/src/astc-encoder/Source/astcenc_ideal_endpoints_and_weights.cpp

Source
// SPDX-License-Identifier: Apache-2.0
// ----------------------------------------------------------------------------
// Copyright 2011-2024 Arm Limited
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at:
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
// ----------------------------------------------------------------------------

#if !defined(ASTCENC_DECOMPRESS_ONLY)

/**
 * @brief Functions for computing color endpoints and texel weights.
 */

#include <cassert>

#include "astcenc_internal.h"
#include "astcenc_vecmathlib.h"

/**
 * @brief Compute the infilled weight for N texel indices in a decimated grid.
 *
 * @param di        The weight grid decimation to use.
 * @param weights   The decimated weight values to use.
 * @param index     The first texel index to interpolate.
 *
 * @return The interpolated weight for the given set of SIMD_WIDTH texels.
 */
static vfloat bilinear_infill_vla(
  const decimation_info& di,
  const float* weights,
  unsigned int index
) {
  // Load the bilinear filter texel weight indexes in the decimated grid
  const uint8_t* weight_idx0 = di.texel_weights_tr[0] + index;
  const uint8_t* weight_idx1 = di.texel_weights_tr[1] + index;
  const uint8_t* weight_idx2 = di.texel_weights_tr[2] + index;
  const uint8_t* weight_idx3 = di.texel_weights_tr[3] + index;

  // Load the bilinear filter weights from the decimated grid
  vfloat weight_val0 = gatherf_byte_inds<vfloat>(weights, weight_idx0);
  vfloat weight_val1 = gatherf_byte_inds<vfloat>(weights, weight_idx1);
  vfloat weight_val2 = gatherf_byte_inds<vfloat>(weights, weight_idx2);
  vfloat weight_val3 = gatherf_byte_inds<vfloat>(weights, weight_idx3);

  // Load the weight contribution factors for each decimated weight
  vfloat tex_weight_float0 = loada(di.texel_weight_contribs_float_tr[0] + index);
  vfloat tex_weight_float1 = loada(di.texel_weight_contribs_float_tr[1] + index);
  vfloat tex_weight_float2 = loada(di.texel_weight_contribs_float_tr[2] + index);
  vfloat tex_weight_float3 = loada(di.texel_weight_contribs_float_tr[3] + index);

  // Compute the bilinear interpolation to generate the per-texel weight
  return (weight_val0 * tex_weight_float0 + weight_val1 * tex_weight_float1) +
         (weight_val2 * tex_weight_float2 + weight_val3 * tex_weight_float3);
}

/**
 * @brief Compute the infilled weight for N texel indices in a decimated grid.
 *
 * This is specialized version which computes only two weights per texel for
 * encodings that are only decimated in a single axis.
 *
 * @param di        The weight grid decimation to use.
 * @param weights   The decimated weight values to use.
 * @param index     The first texel index to interpolate.
 *
 * @return The interpolated weight for the given set of SIMD_WIDTH texels.
 */
static vfloat bilinear_infill_vla_2(
  const decimation_info& di,
  const float* weights,
  unsigned int index
) {
  // Load the bilinear filter texel weight indexes in the decimated grid
  const uint8_t* weight_idx0 = di.texel_weights_tr[0] + index;
  const uint8_t* weight_idx1 = di.texel_weights_tr[1] + index;

  // Load the bilinear filter weights from the decimated grid
  vfloat weight_val0 = gatherf_byte_inds<vfloat>(weights, weight_idx0);
  vfloat weight_val1 = gatherf_byte_inds<vfloat>(weights, weight_idx1);

  // Load the weight contribution factors for each decimated weight
  vfloat tex_weight_float0 = loada(di.texel_weight_contribs_float_tr[0] + index);
  vfloat tex_weight_float1 = loada(di.texel_weight_contribs_float_tr[1] + index);

  // Compute the bilinear interpolation to generate the per-texel weight
  return (weight_val0 * tex_weight_float0 + weight_val1 * tex_weight_float1);
}

/**
 * @brief Compute the ideal endpoints and weights for 1 color component.
 *
 * @param      blk         The image block color data to compress.
 * @param      pi          The partition info for the current trial.
 * @param[out] ei          The computed ideal endpoints and weights.
 * @param      component   The color component to compute.
 */
static void compute_ideal_colors_and_weights_1_comp(
  const image_block& blk,
  const partition_info& pi,
  endpoints_and_weights& ei,
  unsigned int component
) {
  unsigned int partition_count = pi.partition_count;
  ei.ep.partition_count = partition_count;
  promise(partition_count > 0);

  unsigned int texel_count = blk.texel_count;
  promise(texel_count > 0);

  float error_weight;
  const float* data_vr = nullptr;

  assert(component < BLOCK_MAX_COMPONENTS);
  switch (component)
  {
  case 0:
    error_weight = blk.channel_weight.lane<0>();
    data_vr = blk.data_r;
    break;
  case 1:
    error_weight = blk.channel_weight.lane<1>();
    data_vr = blk.data_g;
    break;
  case 2:
    error_weight = blk.channel_weight.lane<2>();
    data_vr = blk.data_b;
    break;
  default:
    assert(component == 3);
    error_weight = blk.channel_weight.lane<3>();
    data_vr = blk.data_a;
    break;
  }

  vmask4 sep_mask = vint4::lane_id() == vint4(component);
  bool is_constant_wes { true };
  float partition0_len_sq { 0.0f };

  for (unsigned int i = 0; i < partition_count; i++)
  {
    float lowvalue { 1e10f };
    float highvalue { -1e10f };

    unsigned int partition_texel_count = pi.partition_texel_count[i];
    for (unsigned int j = 0; j < partition_texel_count; j++)
    {
      unsigned int tix = pi.texels_of_partition[i][j];
      float value = data_vr[tix];
      lowvalue = astc::min(value, lowvalue);
      highvalue = astc::max(value, highvalue);
    }

    if (highvalue <= lowvalue)
    {
      lowvalue = 0.0f;
      highvalue = 1e-7f;
    }

    float length = highvalue - lowvalue;
    float length_squared = length * length;
    float scale = 1.0f / length;

    if (i == 0)
    {
      partition0_len_sq = length_squared;
    }
    else
    {
      is_constant_wes = is_constant_wes && length_squared == partition0_len_sq;
    }

    for (unsigned int j = 0; j < partition_texel_count; j++)
    {
      unsigned int tix = pi.texels_of_partition[i][j];
      float value = (data_vr[tix] - lowvalue) * scale;
      value = astc::clamp1f(value);

      ei.weights[tix] = value;
      ei.weight_error_scale[tix] = length_squared * error_weight;
      assert(!astc::isnan(ei.weight_error_scale[tix]));
    }

    ei.ep.endpt0[i] = select(blk.data_min, vfloat4(lowvalue), sep_mask);
    ei.ep.endpt1[i] = select(blk.data_max, vfloat4(highvalue), sep_mask);
  }

  // Zero initialize any SIMD over-fetch
  size_t texel_count_simd = round_up_to_simd_multiple_vla(texel_count);
  for (size_t i = texel_count; i < texel_count_simd; i++)
  {
    ei.weights[i] = 0.0f;
    ei.weight_error_scale[i] = 0.0f;
  }

  ei.is_constant_weight_error_scale = is_constant_wes;
}

/**
 * @brief Compute the ideal endpoints and weights for 2 color components.
 *
 * @param      blk          The image block color data to compress.
 * @param      pi           The partition info for the current trial.
 * @param[out] ei           The computed ideal endpoints and weights.
 * @param      component1   The first color component to compute.
 * @param      component2   The second color component to compute.
 */
static void compute_ideal_colors_and_weights_2_comp(
  const image_block& blk,
  const partition_info& pi,
  endpoints_and_weights& ei,
  int component1,
  int component2
) {
  unsigned int partition_count = pi.partition_count;
  ei.ep.partition_count = partition_count;
  promise(partition_count > 0);

  unsigned int texel_count = blk.texel_count;
  promise(texel_count > 0);

  partition_metrics pms[BLOCK_MAX_PARTITIONS];

  float error_weight;
  const float* data_vr = nullptr;
  const float* data_vg = nullptr;

  if (component1 == 0 && component2 == 1)
  {
    error_weight = hadd_s(blk.channel_weight.swz<0, 1>()) / 2.0f;

    data_vr = blk.data_r;
    data_vg = blk.data_g;
  }
  else if (component1 == 0 && component2 == 2)
  {
    error_weight = hadd_s(blk.channel_weight.swz<0, 2>()) / 2.0f;

    data_vr = blk.data_r;
    data_vg = blk.data_b;
  }
  else // (component1 == 1 && component2 == 2)
  {
    assert(component1 == 1 && component2 == 2);

    error_weight = hadd_s(blk.channel_weight.swz<1, 2>()) / 2.0f;

    data_vr = blk.data_g;
    data_vg = blk.data_b;
  }

  compute_avgs_and_dirs_2_comp(pi, blk, component1, component2, pms);

  bool is_constant_wes { true };
  float partition0_len_sq { 0.0f };

  vmask4 comp1_mask = vint4::lane_id() == vint4(component1);
  vmask4 comp2_mask = vint4::lane_id() == vint4(component2);

  for (unsigned int i = 0; i < partition_count; i++)
  {
    vfloat4 dir = pms[i].dir;
    if (hadd_s(dir) < 0.0f)
    {
      dir = vfloat4::zero() - dir;
    }

    line2 line { pms[i].avg, normalize_safe(dir, unit2()) };
    float lowparam { 1e10f };
    float highparam { -1e10f };

    unsigned int partition_texel_count = pi.partition_texel_count[i];
    for (unsigned int j = 0; j < partition_texel_count; j++)
    {
      unsigned int tix = pi.texels_of_partition[i][j];
      vfloat4 point = vfloat2(data_vr[tix], data_vg[tix]);
      float param = dot_s(point - line.a, line.b);
      ei.weights[tix] = param;

      lowparam = astc::min(param, lowparam);
      highparam = astc::max(param, highparam);
    }

    // It is possible for a uniform-color partition to produce length=0;
    // this causes NaN issues so set to small value to avoid this problem
    if (highparam <= lowparam)
    {
      lowparam = 0.0f;
      highparam = 1e-7f;
    }

    float length = highparam - lowparam;
    float length_squared = length * length;
    float scale = 1.0f / length;

    if (i == 0)
    {
      partition0_len_sq = length_squared;
    }
    else
    {
      is_constant_wes = is_constant_wes && length_squared == partition0_len_sq;
    }

    for (unsigned int j = 0; j < partition_texel_count; j++)
    {
      unsigned int tix = pi.texels_of_partition[i][j];
      float idx = (ei.weights[tix] - lowparam) * scale;
      idx = astc::clamp1f(idx);

      ei.weights[tix] = idx;
      ei.weight_error_scale[tix] = length_squared * error_weight;
      assert(!astc::isnan(ei.weight_error_scale[tix]));
    }

    vfloat4 lowvalue = line.a + line.b * lowparam;
    vfloat4 highvalue = line.a + line.b * highparam;

    vfloat4 ep0 = select(blk.data_min, vfloat4(lowvalue.lane<0>()), comp1_mask);
    vfloat4 ep1 = select(blk.data_max, vfloat4(highvalue.lane<0>()), comp1_mask);

    ei.ep.endpt0[i] = select(ep0, vfloat4(lowvalue.lane<1>()), comp2_mask);
    ei.ep.endpt1[i] = select(ep1, vfloat4(highvalue.lane<1>()), comp2_mask);
  }

  // Zero initialize any SIMD over-fetch
  size_t texel_count_simd = round_up_to_simd_multiple_vla(texel_count);
  for (size_t i = texel_count; i < texel_count_simd; i++)
  {
    ei.weights[i] = 0.0f;
    ei.weight_error_scale[i] = 0.0f;
  }

  ei.is_constant_weight_error_scale = is_constant_wes;
}

/**
 * @brief Compute the ideal endpoints and weights for 3 color components.
 *
 * @param      blk                 The image block color data to compress.
 * @param      pi                  The partition info for the current trial.
 * @param[out] ei                  The computed ideal endpoints and weights.
 * @param      omitted_component   The color component excluded from the calculation.
 */
static void compute_ideal_colors_and_weights_3_comp(
  const image_block& blk,
  const partition_info& pi,
  endpoints_and_weights& ei,
  unsigned int omitted_component
) {
  unsigned int partition_count = pi.partition_count;
  ei.ep.partition_count = partition_count;
  promise(partition_count > 0);

  unsigned int texel_count = blk.texel_count;
  promise(texel_count > 0);

  partition_metrics pms[BLOCK_MAX_PARTITIONS];

  float error_weight;
  const float* data_vr = nullptr;
  const float* data_vg = nullptr;
  const float* data_vb = nullptr;
  if (omitted_component == 0)
  {
    error_weight = hadd_s(blk.channel_weight.swz<0, 1, 2>());
    data_vr = blk.data_g;
    data_vg = blk.data_b;
    data_vb = blk.data_a;
  }
  else if (omitted_component == 1)
  {
    error_weight = hadd_s(blk.channel_weight.swz<0, 2, 3>());
    data_vr = blk.data_r;
    data_vg = blk.data_b;
    data_vb = blk.data_a;
  }
  else if (omitted_component == 2)
  {
    error_weight = hadd_s(blk.channel_weight.swz<0, 1, 3>());
    data_vr = blk.data_r;
    data_vg = blk.data_g;
    data_vb = blk.data_a;
  }
  else
  {
    assert(omitted_component == 3);

    error_weight = hadd_s(blk.channel_weight.swz<0, 1, 2>());
    data_vr = blk.data_r;
    data_vg = blk.data_g;
    data_vb = blk.data_b;
  }

  error_weight = error_weight * (1.0f / 3.0f);

  if (omitted_component == 3)
  {
    compute_avgs_and_dirs_3_comp_rgb(pi, blk, pms);
  }
  else
  {
    compute_avgs_and_dirs_3_comp(pi, blk, omitted_component, pms);
  }

  bool is_constant_wes { true };
  float partition0_len_sq { 0.0f };

  for (unsigned int i = 0; i < partition_count; i++)
  {
    vfloat4 dir = pms[i].dir;
    if (hadd_rgb_s(dir) < 0.0f)
    {
      dir = vfloat4::zero() - dir;
    }

    line3 line { pms[i].avg, normalize_safe(dir, unit3()) };
    float lowparam { 1e10f };
    float highparam { -1e10f };

    unsigned int partition_texel_count = pi.partition_texel_count[i];
    for (unsigned int j = 0; j < partition_texel_count; j++)
    {
      unsigned int tix = pi.texels_of_partition[i][j];
      vfloat4 point = vfloat3(data_vr[tix], data_vg[tix], data_vb[tix]);
      float param = dot3_s(point - line.a, line.b);
      ei.weights[tix] = param;

      lowparam = astc::min(param, lowparam);
      highparam = astc::max(param, highparam);
    }

    // It is possible for a uniform-color partition to produce length=0;
    // this causes NaN issues so set to small value to avoid this problem
    if (highparam <= lowparam)
    {
      lowparam = 0.0f;
      highparam = 1e-7f;
    }

    float length = highparam - lowparam;
    float length_squared = length * length;
    float scale = 1.0f / length;

    if (i == 0)
    {
      partition0_len_sq = length_squared;
    }
    else
    {
      is_constant_wes = is_constant_wes && length_squared == partition0_len_sq;
    }

    for (unsigned int j = 0; j < partition_texel_count; j++)
    {
      unsigned int tix = pi.texels_of_partition[i][j];
      float idx = (ei.weights[tix] - lowparam) * scale;
      idx = astc::clamp1f(idx);

      ei.weights[tix] = idx;
      ei.weight_error_scale[tix] = length_squared * error_weight;
      assert(!astc::isnan(ei.weight_error_scale[tix]));
    }

    vfloat4 ep0 = line.a + line.b * lowparam;
    vfloat4 ep1 = line.a + line.b * highparam;

    vfloat4 bmin = blk.data_min;
    vfloat4 bmax = blk.data_max;

    assert(omitted_component < BLOCK_MAX_COMPONENTS);
    switch (omitted_component)
    {
      case 0:
        ei.ep.endpt0[i] = vfloat4(bmin.lane<0>(), ep0.lane<0>(), ep0.lane<1>(), ep0.lane<2>());
        ei.ep.endpt1[i] = vfloat4(bmax.lane<0>(), ep1.lane<0>(), ep1.lane<1>(), ep1.lane<2>());
        break;
      case 1:
        ei.ep.endpt0[i] = vfloat4(ep0.lane<0>(), bmin.lane<1>(), ep0.lane<1>(), ep0.lane<2>());
        ei.ep.endpt1[i] = vfloat4(ep1.lane<0>(), bmax.lane<1>(), ep1.lane<1>(), ep1.lane<2>());
        break;
      case 2:
        ei.ep.endpt0[i] = vfloat4(ep0.lane<0>(), ep0.lane<1>(), bmin.lane<2>(), ep0.lane<2>());
        ei.ep.endpt1[i] = vfloat4(ep1.lane<0>(), ep1.lane<1>(), bmax.lane<2>(), ep1.lane<2>());
        break;
      default:
        ei.ep.endpt0[i] = vfloat4(ep0.lane<0>(), ep0.lane<1>(), ep0.lane<2>(), bmin.lane<3>());
        ei.ep.endpt1[i] = vfloat4(ep1.lane<0>(), ep1.lane<1>(), ep1.lane<2>(), bmax.lane<3>());
        break;
    }
  }

  // Zero initialize any SIMD over-fetch
  size_t texel_count_simd = round_up_to_simd_multiple_vla(texel_count);
  for (size_t i = texel_count; i < texel_count_simd; i++)
  {
    ei.weights[i] = 0.0f;
    ei.weight_error_scale[i] = 0.0f;
  }

  ei.is_constant_weight_error_scale = is_constant_wes;
}

/**
 * @brief Compute the ideal endpoints and weights for 4 color components.
 *
 * @param      blk   The image block color data to compress.
 * @param      pi    The partition info for the current trial.
 * @param[out] ei    The computed ideal endpoints and weights.
 */
static void compute_ideal_colors_and_weights_4_comp(
  const image_block& blk,
  const partition_info& pi,
  endpoints_and_weights& ei
) {
  const float error_weight = hadd_s(blk.channel_weight) / 4.0f;

  unsigned int partition_count = pi.partition_count;

  unsigned int texel_count = blk.texel_count;
  promise(texel_count > 0);
  promise(partition_count > 0);

  partition_metrics pms[BLOCK_MAX_PARTITIONS];

  compute_avgs_and_dirs_4_comp(pi, blk, pms);

  bool is_constant_wes { true };
  float partition0_len_sq { 0.0f };

  for (unsigned int i = 0; i < partition_count; i++)
  {
    vfloat4 dir = pms[i].dir;
    if (hadd_rgb_s(dir) < 0.0f)
    {
      dir = vfloat4::zero() - dir;
    }

    line4 line { pms[i].avg, normalize_safe(dir, unit4()) };
    float lowparam { 1e10f };
    float highparam { -1e10f };

    unsigned int partition_texel_count = pi.partition_texel_count[i];
    for (unsigned int j = 0; j < partition_texel_count; j++)
    {
      unsigned int tix = pi.texels_of_partition[i][j];
      vfloat4 point = blk.texel(tix);
      float param = dot_s(point - line.a, line.b);
      ei.weights[tix] = param;

      lowparam = astc::min(param, lowparam);
      highparam = astc::max(param, highparam);
    }

    // It is possible for a uniform-color partition to produce length=0;
    // this causes NaN issues so set to small value to avoid this problem
    if (highparam <= lowparam)
    {
      lowparam = 0.0f;
      highparam = 1e-7f;
    }

    float length = highparam - lowparam;
    float length_squared = length * length;
    float scale = 1.0f / length;

    if (i == 0)
    {
      partition0_len_sq = length_squared;
    }
    else
    {
      is_constant_wes = is_constant_wes && length_squared == partition0_len_sq;
    }

    ei.ep.endpt0[i] = line.a + line.b * lowparam;
    ei.ep.endpt1[i] = line.a + line.b * highparam;

    for (unsigned int j = 0; j < partition_texel_count; j++)
    {
      unsigned int tix = pi.texels_of_partition[i][j];
      float idx = (ei.weights[tix] - lowparam) * scale;
      idx = astc::clamp1f(idx);

      ei.weights[tix] = idx;
      ei.weight_error_scale[tix] = length_squared * error_weight;
      assert(!astc::isnan(ei.weight_error_scale[tix]));
    }
  }

  // Zero initialize any SIMD over-fetch
  size_t texel_count_simd = round_up_to_simd_multiple_vla(texel_count);
  for (size_t i = texel_count; i < texel_count_simd; i++)
  {
    ei.weights[i] = 0.0f;
    ei.weight_error_scale[i] = 0.0f;
  }

  ei.is_constant_weight_error_scale = is_constant_wes;
}

/* See header for documentation. */
void compute_ideal_colors_and_weights_1plane(
  const image_block& blk,
  const partition_info& pi,
  endpoints_and_weights& ei
) {
  bool uses_alpha = !blk.is_constant_channel(3);

  if (uses_alpha)
  {
    compute_ideal_colors_and_weights_4_comp(blk, pi, ei);
  }
  else
  {
    compute_ideal_colors_and_weights_3_comp(blk, pi, ei, 3);
  }
}

/* See header for documentation. */
void compute_ideal_colors_and_weights_2planes(
  const block_size_descriptor& bsd,
  const image_block& blk,
  unsigned int plane2_component,
  endpoints_and_weights& ei1,
  endpoints_and_weights& ei2
) {
  const auto& pi = bsd.get_partition_info(1, 0);
  bool uses_alpha = !blk.is_constant_channel(3);

  assert(plane2_component < BLOCK_MAX_COMPONENTS);
  switch (plane2_component)
  {
  case 0: // Separate weights for red
    if (uses_alpha)
    {
      compute_ideal_colors_and_weights_3_comp(blk, pi, ei1, 0);
    }
    else
    {
      compute_ideal_colors_and_weights_2_comp(blk, pi, ei1, 1, 2);
    }
    compute_ideal_colors_and_weights_1_comp(blk, pi, ei2, 0);
    break;

  case 1: // Separate weights for green
    if (uses_alpha)
    {
      compute_ideal_colors_and_weights_3_comp(blk, pi, ei1, 1);
    }
    else
    {
      compute_ideal_colors_and_weights_2_comp(blk, pi, ei1, 0, 2);
    }
    compute_ideal_colors_and_weights_1_comp(blk, pi, ei2, 1);
    break;

  case 2: // Separate weights for blue
    if (uses_alpha)
    {
      compute_ideal_colors_and_weights_3_comp(blk, pi, ei1, 2);
    }
    else
    {
      compute_ideal_colors_and_weights_2_comp(blk, pi, ei1, 0, 1);
    }
    compute_ideal_colors_and_weights_1_comp(blk, pi, ei2, 2);
    break;

  default: // Separate weights for alpha
    assert(uses_alpha);
    compute_ideal_colors_and_weights_3_comp(blk, pi, ei1, 3);
    compute_ideal_colors_and_weights_1_comp(blk, pi, ei2, 3);
    break;
  }
}

/* See header for documentation. */
float compute_error_of_weight_set_1plane(
  const endpoints_and_weights& eai,
  const decimation_info& di,
  const float* dec_weight_quant_uvalue
) {
  vfloatacc error_summav = vfloatacc::zero();
  unsigned int texel_count = di.texel_count;
  promise(texel_count > 0);

  // Process SIMD-width chunks, safe to over-fetch - the extra space is zero initialized
  if (di.max_texel_weight_count > 2)
  {
    for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      // Compute the bilinear interpolation of the decimated weight grid
      vfloat current_values = bilinear_infill_vla(di, dec_weight_quant_uvalue, i);

      // Compute the error between the computed value and the ideal weight
      vfloat actual_values = loada(eai.weights + i);
      vfloat diff = current_values - actual_values;
      vfloat significance = loada(eai.weight_error_scale + i);
      vfloat error = diff * diff * significance;

      haccumulate(error_summav, error);
    }
  }
  else if (di.max_texel_weight_count > 1)
  {
    for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      // Compute the bilinear interpolation of the decimated weight grid
      vfloat current_values = bilinear_infill_vla_2(di, dec_weight_quant_uvalue, i);

      // Compute the error between the computed value and the ideal weight
      vfloat actual_values = loada(eai.weights + i);
      vfloat diff = current_values - actual_values;
      vfloat significance = loada(eai.weight_error_scale + i);
      vfloat error = diff * diff * significance;

      haccumulate(error_summav, error);
    }
  }
  else
  {
    for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      // Load the weight set directly, without interpolation
      vfloat current_values = loada(dec_weight_quant_uvalue + i);

      // Compute the error between the computed value and the ideal weight
      vfloat actual_values = loada(eai.weights + i);
      vfloat diff = current_values - actual_values;
      vfloat significance = loada(eai.weight_error_scale + i);
      vfloat error = diff * diff * significance;

      haccumulate(error_summav, error);
    }
  }

  // Resolve the final scalar accumulator sum
  return hadd_s(error_summav);
}

/* See header for documentation. */
float compute_error_of_weight_set_2planes(
  const endpoints_and_weights& eai1,
  const endpoints_and_weights& eai2,
  const decimation_info& di,
  const float* dec_weight_quant_uvalue_plane1,
  const float* dec_weight_quant_uvalue_plane2
) {
  vfloatacc error_summav = vfloatacc::zero();
  unsigned int texel_count = di.texel_count;
  promise(texel_count > 0);

  // Process SIMD-width chunks, safe to over-fetch - the extra space is zero initialized
  if (di.max_texel_weight_count > 2)
  {
    for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      // Plane 1
      // Compute the bilinear interpolation of the decimated weight grid
      vfloat current_values1 = bilinear_infill_vla(di, dec_weight_quant_uvalue_plane1, i);

      // Compute the error between the computed value and the ideal weight
      vfloat actual_values1 = loada(eai1.weights + i);
      vfloat diff = current_values1 - actual_values1;
      vfloat error1 = diff * diff * loada(eai1.weight_error_scale + i);

      // Plane 2
      // Compute the bilinear interpolation of the decimated weight grid
      vfloat current_values2 = bilinear_infill_vla(di, dec_weight_quant_uvalue_plane2, i);

      // Compute the error between the computed value and the ideal weight
      vfloat actual_values2 = loada(eai2.weights + i);
      diff = current_values2 - actual_values2;
      vfloat error2 = diff * diff * loada(eai2.weight_error_scale + i);

      haccumulate(error_summav, error1 + error2);
    }
  }
  else if (di.max_texel_weight_count > 1)
  {
    for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      // Plane 1
      // Compute the bilinear interpolation of the decimated weight grid
      vfloat current_values1 = bilinear_infill_vla_2(di, dec_weight_quant_uvalue_plane1, i);

      // Compute the error between the computed value and the ideal weight
      vfloat actual_values1 = loada(eai1.weights + i);
      vfloat diff = current_values1 - actual_values1;
      vfloat error1 = diff * diff * loada(eai1.weight_error_scale + i);

      // Plane 2
      // Compute the bilinear interpolation of the decimated weight grid
      vfloat current_values2 = bilinear_infill_vla_2(di, dec_weight_quant_uvalue_plane2, i);

      // Compute the error between the computed value and the ideal weight
      vfloat actual_values2 = loada(eai2.weights + i);
      diff = current_values2 - actual_values2;
      vfloat error2 = diff * diff * loada(eai2.weight_error_scale + i);

      haccumulate(error_summav, error1 + error2);
    }
  }
  else
  {
    for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      // Plane 1
      // Load the weight set directly, without interpolation
      vfloat current_values1 = loada(dec_weight_quant_uvalue_plane1 + i);

      // Compute the error between the computed value and the ideal weight
      vfloat actual_values1 = loada(eai1.weights + i);
      vfloat diff = current_values1 - actual_values1;
      vfloat error1 = diff * diff * loada(eai1.weight_error_scale + i);

      // Plane 2
      // Load the weight set directly, without interpolation
      vfloat current_values2 = loada(dec_weight_quant_uvalue_plane2 + i);

      // Compute the error between the computed value and the ideal weight
      vfloat actual_values2 = loada(eai2.weights + i);
      diff = current_values2 - actual_values2;
      vfloat error2 = diff * diff * loada(eai2.weight_error_scale + i);

      haccumulate(error_summav, error1 + error2);
    }
  }

  // Resolve the final scalar accumulator sum
  return hadd_s(error_summav);
}

/* See header for documentation. */
void compute_ideal_weights_for_decimation(
  const endpoints_and_weights& ei,
  const decimation_info& di,
  float* dec_weight_ideal_value
) {
  unsigned int texel_count = di.texel_count;
  unsigned int weight_count = di.weight_count;
  bool is_direct = texel_count == weight_count;
  promise(texel_count > 0);
  promise(weight_count > 0);

  // If we have a 1:1 mapping just shortcut the computation. Transfer enough to also copy the
  // zero-initialized SIMD over-fetch region
  if (is_direct)
  {
    for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      vfloat weight(ei.weights + i);
      storea(weight, dec_weight_ideal_value + i);
    }

    return;
  }

  // Otherwise compute an estimate and perform single refinement iteration

  // Compute an initial average for each decimated weight
  bool constant_wes = ei.is_constant_weight_error_scale;
  vfloat weight_error_scale(ei.weight_error_scale[0]);

  // This overshoots - this is OK as we initialize the array tails in the
  // decimation table structures to safe values ...
  for (unsigned int i = 0; i < weight_count; i += ASTCENC_SIMD_WIDTH)
  {
    // Start with a small value to avoid div-by-zero later
    vfloat weight_weight(1e-10f);
    vfloat initial_weight = vfloat::zero();

    // Accumulate error weighting of all the texels using this weight
    vint weight_texel_count(di.weight_texel_count + i);
    unsigned int max_texel_count = hmax_s(weight_texel_count);
    promise(max_texel_count > 0);

    for (unsigned int j = 0; j < max_texel_count; j++)
    {
      const uint8_t* texel = di.weight_texels_tr[j] + i;
      vfloat weight = loada(di.weights_texel_contribs_tr[j] + i);

      if (!constant_wes)
      {
        weight_error_scale = gatherf_byte_inds<vfloat>(ei.weight_error_scale, texel);
      }

      vfloat contrib_weight = weight * weight_error_scale;

      weight_weight += contrib_weight;
      initial_weight += gatherf_byte_inds<vfloat>(ei.weights, texel) * contrib_weight;
    }

    storea(initial_weight / weight_weight, dec_weight_ideal_value + i);
  }

  // Populate the interpolated weight grid based on the initial average
  // Process SIMD-width texel coordinates at at time while we can. Safe to
  // over-process full SIMD vectors - the tail is zeroed.
  ASTCENC_ALIGNAS float infilled_weights[BLOCK_MAX_TEXELS];
  if (di.max_texel_weight_count <= 2)
  {
    for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      vfloat weight = bilinear_infill_vla_2(di, dec_weight_ideal_value, i);
      storea(weight, infilled_weights + i);
    }
  }
  else
  {
    for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      vfloat weight = bilinear_infill_vla(di, dec_weight_ideal_value, i);
      storea(weight, infilled_weights + i);
    }
  }

  // Perform a single iteration of refinement
  // Empirically determined step size; larger values don't help but smaller drops image quality
  constexpr float stepsize = 0.25f;
  constexpr float chd_scale = -WEIGHTS_TEXEL_SUM;

  for (unsigned int i = 0; i < weight_count; i += ASTCENC_SIMD_WIDTH)
  {
    vfloat weight_val = loada(dec_weight_ideal_value + i);

    // Accumulate error weighting of all the texels using this weight
    // Start with a small value to avoid div-by-zero later
    vfloat error_change0(1e-10f);
    vfloat error_change1(0.0f);

    // Accumulate error weighting of all the texels using this weight
    vint weight_texel_count(di.weight_texel_count + i);
    unsigned int max_texel_count = hmax_s(weight_texel_count);
    promise(max_texel_count > 0);

    for (unsigned int j = 0; j < max_texel_count; j++)
    {
      const uint8_t* texel = di.weight_texels_tr[j] + i;
      vfloat contrib_weight = loada(di.weights_texel_contribs_tr[j] + i);

      if (!constant_wes)
      {
        weight_error_scale = gatherf_byte_inds<vfloat>(ei.weight_error_scale, texel);
      }

      vfloat scale = weight_error_scale * contrib_weight;
      vfloat old_weight = gatherf_byte_inds<vfloat>(infilled_weights, texel);
      vfloat ideal_weight = gatherf_byte_inds<vfloat>(ei.weights, texel);

      error_change0 += contrib_weight * scale;
      error_change1 += (old_weight - ideal_weight) * scale;
    }

    vfloat step = (error_change1 * chd_scale) / error_change0;
    step = clamp(-stepsize, stepsize, step);

    // Update the weight; note this can store negative values
    storea(weight_val + step, dec_weight_ideal_value + i);
  }
}

/* See header for documentation. */
void compute_quantized_weights_for_decimation(
  const decimation_info& di,
  float low_bound,
  float high_bound,
  const float* dec_weight_ideal_value,
  float* weight_set_out,
  uint8_t* quantized_weight_set,
  quant_method quant_level
) {
  int weight_count = di.weight_count;
  promise(weight_count > 0);
  const quant_and_transfer_table& qat = quant_and_xfer_tables[quant_level];

  // The available quant levels, stored with a minus 1 bias
  static const float quant_levels_m1[12] {
    1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 7.0f, 9.0f, 11.0f, 15.0f, 19.0f, 23.0f, 31.0f
  };

  vint steps_m1(get_quant_level(quant_level) - 1);
  float quant_level_m1 = quant_levels_m1[quant_level];

  // Quantize the weight set using both the specified low/high bounds and standard 0..1 bounds

  // TODO: Oddity to investigate; triggered by test in issue #265.
  if (high_bound <= low_bound)
  {
    low_bound = 0.0f;
    high_bound = 1.0f;
  }

  float rscale = high_bound - low_bound;
  float scale = 1.0f / rscale;

  float scaled_low_bound = low_bound * scale;
  rscale *= 1.0f / 64.0f;

  vfloat scalev(scale);
  vfloat scaled_low_boundv(scaled_low_bound);
  vfloat quant_level_m1v(quant_level_m1);
  vfloat rscalev(rscale);
  vfloat low_boundv(low_bound);

  // This runs to the rounded-up SIMD size, which is safe as the loop tail is filled with known
  // safe data in compute_ideal_weights_for_decimation and arrays are always 64 elements
  if (get_quant_level(quant_level) <= 16)
  {
    vtable_16x8 table;
    vtable_prepare(table, qat.quant_to_unquant);

    for (int i = 0; i < weight_count; i += ASTCENC_SIMD_WIDTH)
    {
      vfloat ix = loada(dec_weight_ideal_value + i) * scalev - scaled_low_boundv;
      ix = clampzo(ix);

      // Look up the two closest indexes and return the one that was closest
      vfloat ix1 = ix * quant_level_m1v;

      vint weightl = float_to_int(ix1);
      vint weighth = min(weightl + vint(1), steps_m1);

      vint ixli = vtable_lookup_32bit(table, weightl);
      vint ixhi = vtable_lookup_32bit(table, weighth);

      vfloat ixl = int_to_float(ixli);
      vfloat ixh = int_to_float(ixhi);

      vmask mask = (ixl + ixh) < (vfloat(128.0f) * ix);
      vint weight = select(ixli, ixhi, mask);
      ixl = select(ixl, ixh, mask);

      // Invert the weight-scaling that was done initially
      storea(ixl * rscalev + low_boundv, weight_set_out + i);
      pack_and_store_low_bytes(weight, quantized_weight_set + i);
    }
  }
  else
  {
    vtable_32x8 table;
    vtable_prepare(table, qat.quant_to_unquant);

    for (int i = 0; i < weight_count; i += ASTCENC_SIMD_WIDTH)
    {
      vfloat ix = loada(dec_weight_ideal_value + i) * scalev - scaled_low_boundv;
      ix = clampzo(ix);

      // Look up the two closest indexes and return the one that was closest
      vfloat ix1 = ix * quant_level_m1v;

      vint weightl = float_to_int(ix1);
      vint weighth = min(weightl + vint(1), steps_m1);

      vint ixli = vtable_lookup_32bit(table, weightl);
      vint ixhi = vtable_lookup_32bit(table, weighth);

      vfloat ixl = int_to_float(ixli);
      vfloat ixh = int_to_float(ixhi);

      vmask mask = (ixl + ixh) < (vfloat(128.0f) * ix);
      vint weight = select(ixli, ixhi, mask);
      ixl = select(ixl, ixh, mask);

      // Invert the weight-scaling that was done initially
      storea(ixl * rscalev + low_boundv, weight_set_out + i);
      pack_and_store_low_bytes(weight, quantized_weight_set + i);
    }
  }
}

/**
 * @brief Compute the RGB + offset for a HDR endpoint mode #7.
 *
 * Since the matrix needed has a regular structure we can simplify the inverse calculation. This
 * gives us ~24 multiplications vs. 96 for a generic inverse.
 *
 *  mat[0] = vfloat4(rgba_ws.x,      0.0f,      0.0f, wght_ws.x);
 *  mat[1] = vfloat4(     0.0f, rgba_ws.y,      0.0f, wght_ws.y);
 *  mat[2] = vfloat4(     0.0f,      0.0f, rgba_ws.z, wght_ws.z);
 *  mat[3] = vfloat4(wght_ws.x, wght_ws.y, wght_ws.z,      psum);
 *  mat = invert(mat);
 *
 * @param rgba_weight_sum     Sum of partition component error weights.
 * @param weight_weight_sum   Sum of partition component error weights * texel weight.
 * @param rgbq_sum            Sum of partition component error weights * texel weight * color data.
 * @param psum                Sum of RGB color weights * texel weight^2.
 */
static inline vfloat4 compute_rgbo_vector(
  vfloat4 rgba_weight_sum,
  vfloat4 weight_weight_sum,
  vfloat4 rgbq_sum,
  float psum
) {
  float X = rgba_weight_sum.lane<0>();
  float Y = rgba_weight_sum.lane<1>();
  float Z = rgba_weight_sum.lane<2>();
  float P = weight_weight_sum.lane<0>();
  float Q = weight_weight_sum.lane<1>();
  float R = weight_weight_sum.lane<2>();
  float S = psum;

  float PP = P * P;
  float QQ = Q * Q;
  float RR = R * R;

  float SZmRR = S * Z - RR;
  float DT = SZmRR * Y - Z * QQ;
  float YP = Y * P;
  float QX = Q * X;
  float YX = Y * X;
  float mZYP = -Z * YP;
  float mZQX = -Z * QX;
  float mRYX = -R * YX;
  float ZQP = Z * Q * P;
  float RYP = R * YP;
  float RQX = R * QX;

  // Compute the reciprocal of matrix determinant
  float rdet = 1.0f / (DT * X + mZYP * P);

  // Actually compute the adjugate, and then apply 1/det separately
  vfloat4 mat0(DT, ZQP, RYP, mZYP);
  vfloat4 mat1(ZQP, SZmRR * X - Z * PP, RQX, mZQX);
  vfloat4 mat2(RYP, RQX, (S * Y - QQ) * X - Y * PP, mRYX);
  vfloat4 mat3(mZYP, mZQX, mRYX, Z * YX);
  vfloat4 vect = rgbq_sum * rdet;

  return vfloat4(dot_s(mat0, vect),
                 dot_s(mat1, vect),
                 dot_s(mat2, vect),
                 dot_s(mat3, vect));
}

/* See header for documentation. */
void recompute_ideal_colors_1plane(
  const image_block& blk,
  const partition_info& pi,
  const decimation_info& di,
  const uint8_t* dec_weights_uquant,
  endpoints& ep,
  vfloat4 rgbs_vectors[BLOCK_MAX_PARTITIONS],
  vfloat4 rgbo_vectors[BLOCK_MAX_PARTITIONS]
) {
  unsigned int weight_count = di.weight_count;
  unsigned int total_texel_count = blk.texel_count;
  unsigned int partition_count = pi.partition_count;

  promise(weight_count > 0);
  promise(total_texel_count > 0);
  promise(partition_count > 0);

  ASTCENC_ALIGNAS float dec_weight[BLOCK_MAX_WEIGHTS];
  for (unsigned int i = 0; i < weight_count; i += ASTCENC_SIMD_WIDTH)
  {
    vint unquant_value(dec_weights_uquant + i);
    vfloat unquant_valuef = int_to_float(unquant_value) * vfloat(1.0f / 64.0f);
    storea(unquant_valuef, dec_weight + i);
  }

  ASTCENC_ALIGNAS float undec_weight[BLOCK_MAX_TEXELS];
  float* undec_weight_ref;
  if (di.max_texel_weight_count == 1)
  {
    undec_weight_ref = dec_weight;
  }
  else if (di.max_texel_weight_count <= 2)
  {
    for (unsigned int i = 0; i < total_texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      vfloat weight = bilinear_infill_vla_2(di, dec_weight, i);
      storea(weight, undec_weight + i);
    }

    undec_weight_ref = undec_weight;
  }
  else
  {
    for (unsigned int i = 0; i < total_texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      vfloat weight = bilinear_infill_vla(di, dec_weight, i);
      storea(weight, undec_weight + i);
    }

    undec_weight_ref = undec_weight;
  }

  vfloat4 rgba_sum(blk.data_mean * static_cast<float>(blk.texel_count));

  for (unsigned int i = 0; i < partition_count; i++)
  {
    unsigned int texel_count = pi.partition_texel_count[i];
    const uint8_t *texel_indexes = pi.texels_of_partition[i];

    // Only compute a partition mean if more than one partition
    if (partition_count > 1)
    {
      rgba_sum = vfloat4::zero();
      promise(texel_count > 0);
      for (unsigned int j = 0; j < texel_count; j++)
      {
        unsigned int tix = texel_indexes[j];
        rgba_sum += blk.texel(tix);
      }
    }

    rgba_sum = rgba_sum * blk.channel_weight;
    vfloat4 rgba_weight_sum = max(blk.channel_weight * static_cast<float>(texel_count), 1e-17f);
    vfloat4 scale_dir = normalize((rgba_sum / rgba_weight_sum).swz<0, 1, 2>());

    float scale_max = 0.0f;
    float scale_min = 1e10f;

    float wmin1 = 1.0f;
    float wmax1 = 0.0f;

    float left_sum_s = 0.0f;
    float middle_sum_s = 0.0f;
    float right_sum_s = 0.0f;

    vfloat4 color_vec_x = vfloat4::zero();
    vfloat4 color_vec_y = vfloat4::zero();

    vfloat4 scale_vec = vfloat4::zero();

    float weight_weight_sum_s = 1e-17f;

    vfloat4 color_weight = blk.channel_weight;
    float ls_weight = hadd_rgb_s(color_weight);

    for (unsigned int j = 0; j < texel_count; j++)
    {
      unsigned int tix = texel_indexes[j];
      vfloat4 rgba = blk.texel(tix);

      float idx0 = undec_weight_ref[tix];

      float om_idx0 = 1.0f - idx0;
      wmin1 = astc::min(idx0, wmin1);
      wmax1 = astc::max(idx0, wmax1);

      float scale = dot3_s(scale_dir, rgba);
      scale_min = astc::min(scale, scale_min);
      scale_max = astc::max(scale, scale_max);

      left_sum_s   += om_idx0 * om_idx0;
      middle_sum_s += om_idx0 * idx0;
      right_sum_s  += idx0 * idx0;
      weight_weight_sum_s += idx0;

      vfloat4 color_idx(idx0);
      vfloat4 cwprod = rgba;
      vfloat4 cwiprod = cwprod * color_idx;

      color_vec_y += cwiprod;
      color_vec_x += cwprod - cwiprod;

      scale_vec += vfloat2(om_idx0, idx0) * (scale * ls_weight);
    }

    vfloat4 left_sum   = vfloat4(left_sum_s) * color_weight;
    vfloat4 middle_sum = vfloat4(middle_sum_s) * color_weight;
    vfloat4 right_sum  = vfloat4(right_sum_s) * color_weight;
    vfloat4 lmrs_sum   = vfloat3(left_sum_s, middle_sum_s, right_sum_s) * ls_weight;

    color_vec_x = color_vec_x * color_weight;
    color_vec_y = color_vec_y * color_weight;

    // Initialize the luminance and scale vectors with a reasonable default
    float scalediv = scale_min / astc::max(scale_max, 1e-10f);
    scalediv = astc::clamp1f(scalediv);

    vfloat4 sds = scale_dir * scale_max;

    rgbs_vectors[i] = vfloat4(sds.lane<0>(), sds.lane<1>(), sds.lane<2>(), scalediv);

    if (wmin1 >= wmax1 * 0.999f)
    {
      // If all weights in the partition were equal, then just take average of all colors in
      // the partition and use that as both endpoint colors
      vfloat4 avg = (color_vec_x + color_vec_y) / rgba_weight_sum;

      vmask4 notnan_mask = avg == avg;
      ep.endpt0[i] = select(ep.endpt0[i], avg, notnan_mask);
      ep.endpt1[i] = select(ep.endpt1[i], avg, notnan_mask);

      rgbs_vectors[i] = vfloat4(sds.lane<0>(), sds.lane<1>(), sds.lane<2>(), 1.0f);
    }
    else
    {
      // Otherwise, complete the analytic calculation of ideal-endpoint-values for the given
      // set of texel weights and pixel colors
      vfloat4 color_det1 = (left_sum * right_sum) - (middle_sum * middle_sum);
      vfloat4 color_rdet1 = 1.0f / color_det1;

      float ls_det1  = (lmrs_sum.lane<0>() * lmrs_sum.lane<2>()) - (lmrs_sum.lane<1>() * lmrs_sum.lane<1>());
      float ls_rdet1 = 1.0f / ls_det1;

      vfloat4 color_mss1 = (left_sum * left_sum)
                         + (2.0f * middle_sum * middle_sum)
                         + (right_sum * right_sum);

      float ls_mss1 = (lmrs_sum.lane<0>() * lmrs_sum.lane<0>())
                    + (2.0f * lmrs_sum.lane<1>() * lmrs_sum.lane<1>())
                    + (lmrs_sum.lane<2>() * lmrs_sum.lane<2>());

      vfloat4 ep0 = (right_sum * color_vec_x - middle_sum * color_vec_y) * color_rdet1;
      vfloat4 ep1 = (left_sum * color_vec_y - middle_sum * color_vec_x) * color_rdet1;

      vmask4 det_mask = abs(color_det1) > (color_mss1 * 1e-4f);
      vmask4 notnan_mask = (ep0 == ep0) & (ep1 == ep1);
      vmask4 full_mask = det_mask & notnan_mask;

      ep.endpt0[i] = select(ep.endpt0[i], ep0, full_mask);
      ep.endpt1[i] = select(ep.endpt1[i], ep1, full_mask);

      float scale_ep0 = (lmrs_sum.lane<2>() * scale_vec.lane<0>() - lmrs_sum.lane<1>() * scale_vec.lane<1>()) * ls_rdet1;
      float scale_ep1 = (lmrs_sum.lane<0>() * scale_vec.lane<1>() - lmrs_sum.lane<1>() * scale_vec.lane<0>()) * ls_rdet1;

      if (fabsf(ls_det1) > (ls_mss1 * 1e-4f) && scale_ep0 == scale_ep0 && scale_ep1 == scale_ep1 && scale_ep0 < scale_ep1)
      {
        float scalediv2 = scale_ep0 / scale_ep1;
        vfloat4 sdsm = scale_dir * scale_ep1;
        rgbs_vectors[i] = vfloat4(sdsm.lane<0>(), sdsm.lane<1>(), sdsm.lane<2>(), scalediv2);
      }
    }

    // Calculations specific to mode #7, the HDR RGB-scale mode - skip if known LDR
    if (blk.rgb_lns[0] || blk.alpha_lns[0])
    {
      vfloat4 weight_weight_sum = vfloat4(weight_weight_sum_s) * color_weight;
      float psum = right_sum_s * hadd_rgb_s(color_weight);

      vfloat4 rgbq_sum = color_vec_x + color_vec_y;
      rgbq_sum.set_lane<3>(hadd_rgb_s(color_vec_y));

      vfloat4 rgbovec = compute_rgbo_vector(rgba_weight_sum, weight_weight_sum, rgbq_sum, psum);
      rgbo_vectors[i] = rgbovec;

      // We can get a failure due to the use of a singular (non-invertible) matrix
      // If it failed, compute rgbo_vectors[] with a different method ...
      if (astc::isnan(dot_s(rgbovec, rgbovec)))
      {
        vfloat4 v0 = ep.endpt0[i];
        vfloat4 v1 = ep.endpt1[i];

        float avgdif = hadd_rgb_s(v1 - v0) * (1.0f / 3.0f);
        avgdif = astc::max(avgdif, 0.0f);

        vfloat4 avg = (v0 + v1) * 0.5f;
        vfloat4 ep0 = avg - vfloat4(avgdif) * 0.5f;
        rgbo_vectors[i] = vfloat4(ep0.lane<0>(), ep0.lane<1>(), ep0.lane<2>(), avgdif);
      }
    }
  }
}

/* See header for documentation. */
void recompute_ideal_colors_2planes(
  const image_block& blk,
  const block_size_descriptor& bsd,
  const decimation_info& di,
  const uint8_t* dec_weights_uquant_plane1,
  const uint8_t* dec_weights_uquant_plane2,
  endpoints& ep,
  vfloat4& rgbs_vector,
  vfloat4& rgbo_vector,
  int plane2_component
) {
  unsigned int weight_count = di.weight_count;
  unsigned int total_texel_count = blk.texel_count;

  promise(total_texel_count > 0);
  promise(weight_count > 0);

  ASTCENC_ALIGNAS float dec_weight_plane1[BLOCK_MAX_WEIGHTS_2PLANE];
  ASTCENC_ALIGNAS float dec_weight_plane2[BLOCK_MAX_WEIGHTS_2PLANE];

  assert(weight_count <= BLOCK_MAX_WEIGHTS_2PLANE);

  for (unsigned int i = 0; i < weight_count; i += ASTCENC_SIMD_WIDTH)
  {
    vint unquant_value1(dec_weights_uquant_plane1 + i);
    vfloat unquant_value1f = int_to_float(unquant_value1) * vfloat(1.0f / 64.0f);
    storea(unquant_value1f, dec_weight_plane1 + i);

    vint unquant_value2(dec_weights_uquant_plane2 + i);
    vfloat unquant_value2f = int_to_float(unquant_value2) * vfloat(1.0f / 64.0f);
    storea(unquant_value2f, dec_weight_plane2 + i);
  }

  ASTCENC_ALIGNAS float undec_weight_plane1[BLOCK_MAX_TEXELS];
  ASTCENC_ALIGNAS float undec_weight_plane2[BLOCK_MAX_TEXELS];

  float* undec_weight_plane1_ref;
  float* undec_weight_plane2_ref;

  if (di.max_texel_weight_count == 1)
  {
    undec_weight_plane1_ref = dec_weight_plane1;
    undec_weight_plane2_ref = dec_weight_plane2;
  }
  else if (di.max_texel_weight_count <= 2)
  {
    for (unsigned int i = 0; i < total_texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      vfloat weight = bilinear_infill_vla_2(di, dec_weight_plane1, i);
      storea(weight, undec_weight_plane1 + i);

      weight = bilinear_infill_vla_2(di, dec_weight_plane2, i);
      storea(weight, undec_weight_plane2 + i);
    }

    undec_weight_plane1_ref = undec_weight_plane1;
    undec_weight_plane2_ref = undec_weight_plane2;
  }
  else
  {
    for (unsigned int i = 0; i < total_texel_count; i += ASTCENC_SIMD_WIDTH)
    {
      vfloat weight = bilinear_infill_vla(di, dec_weight_plane1, i);
      storea(weight, undec_weight_plane1 + i);

      weight = bilinear_infill_vla(di, dec_weight_plane2, i);
      storea(weight, undec_weight_plane2 + i);
    }

    undec_weight_plane1_ref = undec_weight_plane1;
    undec_weight_plane2_ref = undec_weight_plane2;
  }

  unsigned int texel_count = bsd.texel_count;
  vfloat4 rgba_weight_sum = max(blk.channel_weight * static_cast<float>(texel_count), 1e-17f);
  vfloat4 scale_dir = normalize(blk.data_mean.swz<0, 1, 2>());

  float scale_max = 0.0f;
  float scale_min = 1e10f;

  float wmin1 = 1.0f;
  float wmax1 = 0.0f;

  float wmin2 = 1.0f;
  float wmax2 = 0.0f;

  float left1_sum_s = 0.0f;
  float middle1_sum_s = 0.0f;
  float right1_sum_s = 0.0f;

  float left2_sum_s = 0.0f;
  float middle2_sum_s = 0.0f;
  float right2_sum_s = 0.0f;

  vfloat4 color_vec_x = vfloat4::zero();
  vfloat4 color_vec_y = vfloat4::zero();

  vfloat4 scale_vec = vfloat4::zero();

  vfloat4 weight_weight_sum = vfloat4(1e-17f);

  vmask4 p2_mask = vint4::lane_id() == vint4(plane2_component);
  vfloat4 color_weight = blk.channel_weight;
  float ls_weight = hadd_rgb_s(color_weight);

  for (unsigned int j = 0; j < texel_count; j++)
  {
    vfloat4 rgba = blk.texel(j);

    float idx0 = undec_weight_plane1_ref[j];

    float om_idx0 = 1.0f - idx0;
    wmin1 = astc::min(idx0, wmin1);
    wmax1 = astc::max(idx0, wmax1);

    float scale = dot3_s(scale_dir, rgba);
    scale_min = astc::min(scale, scale_min);
    scale_max = astc::max(scale, scale_max);

    left1_sum_s   += om_idx0 * om_idx0;
    middle1_sum_s += om_idx0 * idx0;
    right1_sum_s  += idx0 * idx0;

    float idx1 = undec_weight_plane2_ref[j];

    float om_idx1 = 1.0f - idx1;
    wmin2 = astc::min(idx1, wmin2);
    wmax2 = astc::max(idx1, wmax2);

    left2_sum_s   += om_idx1 * om_idx1;
    middle2_sum_s += om_idx1 * idx1;
    right2_sum_s  += idx1 * idx1;

    vfloat4 color_idx = select(vfloat4(idx0), vfloat4(idx1), p2_mask);

    vfloat4 cwprod = rgba;
    vfloat4 cwiprod = cwprod * color_idx;

    color_vec_y += cwiprod;
    color_vec_x += cwprod - cwiprod;

    scale_vec += vfloat2(om_idx0, idx0) * (ls_weight * scale);
    weight_weight_sum += color_idx;
  }

  vfloat4 left1_sum   = vfloat4(left1_sum_s) * color_weight;
  vfloat4 middle1_sum = vfloat4(middle1_sum_s) * color_weight;
  vfloat4 right1_sum  = vfloat4(right1_sum_s) * color_weight;
  vfloat4 lmrs_sum    = vfloat3(left1_sum_s, middle1_sum_s, right1_sum_s) * ls_weight;

  vfloat4 left2_sum   = vfloat4(left2_sum_s) * color_weight;
  vfloat4 middle2_sum = vfloat4(middle2_sum_s) * color_weight;
  vfloat4 right2_sum  = vfloat4(right2_sum_s) * color_weight;

  color_vec_x = color_vec_x * color_weight;
  color_vec_y = color_vec_y * color_weight;

  // Initialize the luminance and scale vectors with a reasonable default
  float scalediv = scale_min / astc::max(scale_max, 1e-10f);
  scalediv = astc::clamp1f(scalediv);

  vfloat4 sds = scale_dir * scale_max;

  rgbs_vector = vfloat4(sds.lane<0>(), sds.lane<1>(), sds.lane<2>(), scalediv);

  if (wmin1 >= wmax1 * 0.999f)
  {
    // If all weights in the partition were equal, then just take average of all colors in
    // the partition and use that as both endpoint colors
    vfloat4 avg = (color_vec_x + color_vec_y) / rgba_weight_sum;

    vmask4 p1_mask = vint4::lane_id() != vint4(plane2_component);
    vmask4 notnan_mask = avg == avg;
    vmask4 full_mask = p1_mask & notnan_mask;

    ep.endpt0[0] = select(ep.endpt0[0], avg, full_mask);
    ep.endpt1[0] = select(ep.endpt1[0], avg, full_mask);

    rgbs_vector = vfloat4(sds.lane<0>(), sds.lane<1>(), sds.lane<2>(), 1.0f);
  }
  else
  {
    // Otherwise, complete the analytic calculation of ideal-endpoint-values for the given
    // set of texel weights and pixel colors
    vfloat4 color_det1 = (left1_sum * right1_sum) - (middle1_sum * middle1_sum);
    vfloat4 color_rdet1 = 1.0f / color_det1;

    float ls_det1  = (lmrs_sum.lane<0>() * lmrs_sum.lane<2>()) - (lmrs_sum.lane<1>() * lmrs_sum.lane<1>());
    float ls_rdet1 = 1.0f / ls_det1;

    vfloat4 color_mss1 = (left1_sum * left1_sum)
                       + (2.0f * middle1_sum * middle1_sum)
                       + (right1_sum * right1_sum);

    float ls_mss1 = (lmrs_sum.lane<0>() * lmrs_sum.lane<0>())
                  + (2.0f * lmrs_sum.lane<1>() * lmrs_sum.lane<1>())
                  + (lmrs_sum.lane<2>() * lmrs_sum.lane<2>());

    vfloat4 ep0 = (right1_sum * color_vec_x - middle1_sum * color_vec_y) * color_rdet1;
    vfloat4 ep1 = (left1_sum * color_vec_y - middle1_sum * color_vec_x) * color_rdet1;

    float scale_ep0 = (lmrs_sum.lane<2>() * scale_vec.lane<0>() - lmrs_sum.lane<1>() * scale_vec.lane<1>()) * ls_rdet1;
    float scale_ep1 = (lmrs_sum.lane<0>() * scale_vec.lane<1>() - lmrs_sum.lane<1>() * scale_vec.lane<0>()) * ls_rdet1;

    vmask4 p1_mask = vint4::lane_id() != vint4(plane2_component);
    vmask4 det_mask = abs(color_det1) > (color_mss1 * 1e-4f);
    vmask4 notnan_mask = (ep0 == ep0) & (ep1 == ep1);
    vmask4 full_mask = p1_mask & det_mask & notnan_mask;

    ep.endpt0[0] = select(ep.endpt0[0], ep0, full_mask);
    ep.endpt1[0] = select(ep.endpt1[0], ep1, full_mask);

    if (fabsf(ls_det1) > (ls_mss1 * 1e-4f) && scale_ep0 == scale_ep0 && scale_ep1 == scale_ep1 && scale_ep0 < scale_ep1)
    {
      float scalediv2 = scale_ep0 / scale_ep1;
      vfloat4 sdsm = scale_dir * scale_ep1;
      rgbs_vector = vfloat4(sdsm.lane<0>(), sdsm.lane<1>(), sdsm.lane<2>(), scalediv2);
    }
  }

  if (wmin2 >= wmax2 * 0.999f)
  {
    // If all weights in the partition were equal, then just take average of all colors in
    // the partition and use that as both endpoint colors
    vfloat4 avg = (color_vec_x + color_vec_y) / rgba_weight_sum;

    vmask4 notnan_mask = avg == avg;
    vmask4 full_mask = p2_mask & notnan_mask;

    ep.endpt0[0] = select(ep.endpt0[0], avg, full_mask);
    ep.endpt1[0] = select(ep.endpt1[0], avg, full_mask);
  }
  else
  {
    // Otherwise, complete the analytic calculation of ideal-endpoint-values for the given
    // set of texel weights and pixel colors
    vfloat4 color_det2 = (left2_sum * right2_sum) - (middle2_sum * middle2_sum);
    vfloat4 color_rdet2 = 1.0f / color_det2;

    vfloat4 color_mss2 = (left2_sum * left2_sum)
                       + (2.0f * middle2_sum * middle2_sum)
                       + (right2_sum * right2_sum);

    vfloat4 ep0 = (right2_sum * color_vec_x - middle2_sum * color_vec_y) * color_rdet2;
    vfloat4 ep1 = (left2_sum * color_vec_y - middle2_sum * color_vec_x) * color_rdet2;

    vmask4 det_mask = abs(color_det2) > (color_mss2 * 1e-4f);
    vmask4 notnan_mask = (ep0 == ep0) & (ep1 == ep1);
    vmask4 full_mask = p2_mask & det_mask & notnan_mask;

    ep.endpt0[0] = select(ep.endpt0[0], ep0, full_mask);
    ep.endpt1[0] = select(ep.endpt1[0], ep1, full_mask);
  }

  // Calculations specific to mode #7, the HDR RGB-scale mode - skip if known LDR
  if (blk.rgb_lns[0] || blk.alpha_lns[0])
  {
    weight_weight_sum = weight_weight_sum * color_weight;
    float psum = dot3_s(select(right1_sum, right2_sum, p2_mask), color_weight);

    vfloat4 rgbq_sum = color_vec_x + color_vec_y;
    rgbq_sum.set_lane<3>(hadd_rgb_s(color_vec_y));

    rgbo_vector = compute_rgbo_vector(rgba_weight_sum, weight_weight_sum, rgbq_sum, psum);

    // We can get a failure due to the use of a singular (non-invertible) matrix
    // If it failed, compute rgbo_vectors[] with a different method ...
    if (astc::isnan(dot_s(rgbo_vector, rgbo_vector)))
    {
      vfloat4 v0 = ep.endpt0[0];
      vfloat4 v1 = ep.endpt1[0];

      float avgdif = hadd_rgb_s(v1 - v0) * (1.0f / 3.0f);
      avgdif = astc::max(avgdif, 0.0f);

      vfloat4 avg = (v0 + v1) * 0.5f;
      vfloat4 ep0 = avg - vfloat4(avgdif) * 0.5f;

      rgbo_vector = vfloat4(ep0.lane<0>(), ep0.lane<1>(), ep0.lane<2>(), avgdif);
    }
  }
}

#endif

Coverage Report

Created: 2026-09-01 06:58