/*

 * jcsample.c

 *

 * This file was part of the Independent JPEG Group's software:

 * Copyright (C) 1991-1996, Thomas G. Lane.

 * Lossless JPEG Modifications:

 * Copyright (C) 1999, Ken Murchison.

 * libjpeg-turbo Modifications:

 * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB

 * Copyright (C) 2014, MIPS Technologies, Inc., California.

 * Copyright (C) 2015, 2019, 2022, D. R. Commander.

 * For conditions of distribution and use, see the accompanying README.ijg

 * file.

 *

 * This file contains downsampling routines.

 *

 * Downsampling input data is counted in "row groups".  A row group

 * is defined to be max_v_samp_factor pixel rows of each component,

 * from which the downsampler produces v_samp_factor sample rows.

 * A single row group is processed in each call to the downsampler module.

 *

 * The downsampler is responsible for edge-expansion of its output data

 * to fill an integral number of DCT blocks horizontally.  The source buffer

 * may be modified if it is helpful for this purpose (the source buffer is

 * allocated wide enough to correspond to the desired output width).

 * The caller (the prep controller) is responsible for vertical padding.

 *

 * The downsampler may request "context rows" by setting need_context_rows

 * during startup.  In this case, the input arrays will contain at least

 * one row group's worth of pixels above and below the passed-in data;

 * the caller will create dummy rows at image top and bottom by replicating

 * the first or last real pixel row.

 *

 * An excellent reference for image resampling is

 *   Digital Image Warping, George Wolberg, 1990.

 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.

 *

 * The downsampling algorithm used here is a simple average of the source

 * pixels covered by the output pixel.  The hi-falutin sampling literature

 * refers to this as a "box filter".  In general the characteristics of a box

 * filter are not very good, but for the specific cases we normally use (1:1

 * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not

 * nearly so bad.  If you intend to use other sampling ratios, you'd be well

 * advised to improve this code.

 *

 * A simple input-smoothing capability is provided.  This is mainly intended

 * for cleaning up color-dithered GIF input files (if you find it inadequate,

 * we suggest using an external filtering program such as pnmconvol).  When

 * enabled, each input pixel P is replaced by a weighted sum of itself and its

 * eight neighbors.  P's weight is 1-8*SF and each neighbor's weight is SF,

 * where SF = (smoothing_factor / 1024).

 * Currently, smoothing is only supported for 2h2v sampling factors.

 */

#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

#include "jsimd.h"

#include "jsamplecomp.h"

#if BITS_IN_JSAMPLE != 16 || defined(C_LOSSLESS_SUPPORTED)

/* Pointer to routine to downsample a single component */

typedef void (*downsample1_ptr) (j_compress_ptr cinfo,

                                 jpeg_component_info *compptr,

                                 _JSAMPARRAY input_data,

                                 _JSAMPARRAY output_data);

/* Private subobject */

typedef struct {

  struct jpeg_downsampler pub;  /* public fields */

  /* Downsampling method pointers, one per component */

  downsample1_ptr methods[MAX_COMPONENTS];

} my_downsampler;

typedef my_downsampler *my_downsample_ptr;

/*

 * Initialize for a downsampling pass.

 */

METHODDEF(void)

start_pass_downsample(j_compress_ptr cinfo)

{

  /* no work for now */

}

/*

 * Expand a component horizontally from width input_cols to width output_cols,

 * by duplicating the rightmost samples.

 */

LOCAL(void)

expand_right_edge(_JSAMPARRAY image_data, int num_rows, JDIMENSION input_cols,

                  JDIMENSION output_cols)

{

  register _JSAMPROW ptr;

  register _JSAMPLE pixval;

  register int count;

  int row;

  int numcols = (int)(output_cols - input_cols);

  if (numcols > 0) {

    for (row = 0; row < num_rows; row++) {

      ptr = image_data[row] + input_cols;

      pixval = ptr[-1];

      for (count = numcols; count > 0; count--)

        *ptr++ = pixval;

    }

  }

}

/*

 * Do downsampling for a whole row group (all components).

 *

 * In this version we simply downsample each component independently.

 */

METHODDEF(void)

sep_downsample(j_compress_ptr cinfo, _JSAMPIMAGE input_buf,

               JDIMENSION in_row_index, _JSAMPIMAGE output_buf,

               JDIMENSION out_row_group_index)

{

  my_downsample_ptr downsample = (my_downsample_ptr)cinfo->downsample;

  int ci;

  jpeg_component_info *compptr;

  _JSAMPARRAY in_ptr, out_ptr;

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    in_ptr = input_buf[ci] + in_row_index;

    out_ptr = output_buf[ci] + (out_row_group_index * compptr->v_samp_factor);

    (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr);

  }

}

/*

 * Downsample pixel values of a single component.

 * One row group is processed per call.

 * This version handles arbitrary integral sampling ratios, without smoothing.

 * Note that this version is not actually used for customary sampling ratios.

 */

METHODDEF(void)

int_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,

               _JSAMPARRAY input_data, _JSAMPARRAY output_data)

{

  int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;

  JDIMENSION outcol, outcol_h;  /* outcol_h == outcol*h_expand */

  int data_unit = cinfo->master->lossless ? 1 : DCTSIZE;

  JDIMENSION output_cols = compptr->width_in_blocks * data_unit;

  _JSAMPROW inptr, outptr;

  JLONG outvalue;

  h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;

  v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;

  numpix = h_expand * v_expand;

  numpix2 = numpix / 2;

  /* Expand input data enough to let all the output samples be generated

   * by the standard loop.  Special-casing padded output would be more

   * efficient.

   */

  expand_right_edge(input_data, cinfo->max_v_samp_factor, cinfo->image_width,

                    output_cols * h_expand);

  inrow = 0;

  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

    outptr = output_data[outrow];

    for (outcol = 0, outcol_h = 0; outcol < output_cols;

         outcol++, outcol_h += h_expand) {

      outvalue = 0;

      for (v = 0; v < v_expand; v++) {

        inptr = input_data[inrow + v] + outcol_h;

        for (h = 0; h < h_expand; h++) {

          outvalue += (JLONG)(*inptr++);

        }

      }

      *outptr++ = (_JSAMPLE)((outvalue + numpix2) / numpix);

    }

    inrow += v_expand;

  }

}

/*

 * Downsample pixel values of a single component.

 * This version handles the special case of a full-size component,

 * without smoothing.

 */

METHODDEF(void)

fullsize_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,

                    _JSAMPARRAY input_data, _JSAMPARRAY output_data)

{

  int data_unit = cinfo->master->lossless ? 1 : DCTSIZE;

  /* Copy the data */

  _jcopy_sample_rows(input_data, 0, output_data, 0, cinfo->max_v_samp_factor,

                     cinfo->image_width);

  /* Edge-expand */

  expand_right_edge(output_data, cinfo->max_v_samp_factor, cinfo->image_width,

                    compptr->width_in_blocks * data_unit);

}

/*

 * Downsample pixel values of a single component.

 * This version handles the common case of 2:1 horizontal and 1:1 vertical,

 * without smoothing.

 *

 * A note about the "bias" calculations: when rounding fractional values to

 * integer, we do not want to always round 0.5 up to the next integer.

 * If we did that, we'd introduce a noticeable bias towards larger values.

 * Instead, this code is arranged so that 0.5 will be rounded up or down at

 * alternate pixel locations (a simple ordered dither pattern).

 */

METHODDEF(void)

h2v1_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,

                _JSAMPARRAY input_data, _JSAMPARRAY output_data)

{

  int outrow;

  JDIMENSION outcol;

  int data_unit = cinfo->master->lossless ? 1 : DCTSIZE;

  JDIMENSION output_cols = compptr->width_in_blocks * data_unit;

  register _JSAMPROW inptr, outptr;

  register int bias;

  /* Expand input data enough to let all the output samples be generated

   * by the standard loop.  Special-casing padded output would be more

   * efficient.

   */

  expand_right_edge(input_data, cinfo->max_v_samp_factor, cinfo->image_width,

                    output_cols * 2);

  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

    outptr = output_data[outrow];

    inptr = input_data[outrow];

    bias = 0;                   /* bias = 0,1,0,1,... for successive samples */

    for (outcol = 0; outcol < output_cols; outcol++) {

      *outptr++ = (_JSAMPLE)((inptr[0] + inptr[1] + bias) >> 1);

      bias ^= 1;                /* 0=>1, 1=>0 */

      inptr += 2;

    }

  }

}

/*

 * Downsample pixel values of a single component.

 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,

 * without smoothing.

 */

METHODDEF(void)

h2v2_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,

                _JSAMPARRAY input_data, _JSAMPARRAY output_data)

{

  int inrow, outrow;

  JDIMENSION outcol;

  int data_unit = cinfo->master->lossless ? 1 : DCTSIZE;

  JDIMENSION output_cols = compptr->width_in_blocks * data_unit;

  register _JSAMPROW inptr0, inptr1, outptr;

  register int bias;

  /* Expand input data enough to let all the output samples be generated

   * by the standard loop.  Special-casing padded output would be more

   * efficient.

   */

  expand_right_edge(input_data, cinfo->max_v_samp_factor, cinfo->image_width,

                    output_cols * 2);

  inrow = 0;

  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

    outptr = output_data[outrow];

    inptr0 = input_data[inrow];

    inptr1 = input_data[inrow + 1];

    bias = 1;                   /* bias = 1,2,1,2,... for successive samples */

    for (outcol = 0; outcol < output_cols; outcol++) {

      *outptr++ = (_JSAMPLE)

        ((inptr0[0] + inptr0[1] + inptr1[0] + inptr1[1] + bias) >> 2);

      bias ^= 3;                /* 1=>2, 2=>1 */

      inptr0 += 2;  inptr1 += 2;

    }

    inrow += 2;

  }

}

#ifdef INPUT_SMOOTHING_SUPPORTED

/*

 * Downsample pixel values of a single component.

 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,

 * with smoothing.  One row of context is required.

 */

METHODDEF(void)

h2v2_smooth_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,

                       _JSAMPARRAY input_data, _JSAMPARRAY output_data)

{

  int inrow, outrow;

  JDIMENSION colctr;

  int data_unit = cinfo->master->lossless ? 1 : DCTSIZE;

  JDIMENSION output_cols = compptr->width_in_blocks * data_unit;

  register _JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;

  JLONG membersum, neighsum, memberscale, neighscale;

  /* Expand input data enough to let all the output samples be generated

   * by the standard loop.  Special-casing padded output would be more

   * efficient.

   */

  expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,

                    cinfo->image_width, output_cols * 2);

  /* We don't bother to form the individual "smoothed" input pixel values;

   * we can directly compute the output which is the average of the four

   * smoothed values.  Each of the four member pixels contributes a fraction

   * (1-8*SF) to its own smoothed image and a fraction SF to each of the three

   * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final

   * output.  The four corner-adjacent neighbor pixels contribute a fraction

   * SF to just one smoothed pixel, or SF/4 to the final output; while the

   * eight edge-adjacent neighbors contribute SF to each of two smoothed

   * pixels, or SF/2 overall.  In order to use integer arithmetic, these

   * factors are scaled by 2^16 = 65536.

   * Also recall that SF = smoothing_factor / 1024.

   */

  memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */

  neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */

  inrow = 0;

  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

    outptr = output_data[outrow];

    inptr0 = input_data[inrow];

    inptr1 = input_data[inrow + 1];

    above_ptr = input_data[inrow - 1];

    below_ptr = input_data[inrow + 2];

    /* Special case for first column: pretend column -1 is same as column 0 */

    membersum = inptr0[0] + inptr0[1] + inptr1[0] + inptr1[1];

    neighsum = above_ptr[0] + above_ptr[1] + below_ptr[0] + below_ptr[1] +

               inptr0[0] + inptr0[2] + inptr1[0] + inptr1[2];

    neighsum += neighsum;

    neighsum += above_ptr[0] + above_ptr[2] + below_ptr[0] + below_ptr[2];

    membersum = membersum * memberscale + neighsum * neighscale;

    *outptr++ = (_JSAMPLE)((membersum + 32768) >> 16);

    inptr0 += 2;  inptr1 += 2;  above_ptr += 2;  below_ptr += 2;

    for (colctr = output_cols - 2; colctr > 0; colctr--) {

      /* sum of pixels directly mapped to this output element */

      membersum = inptr0[0] + inptr0[1] + inptr1[0] + inptr1[1];

      /* sum of edge-neighbor pixels */

      neighsum = above_ptr[0] + above_ptr[1] + below_ptr[0] + below_ptr[1] +

                 inptr0[-1] + inptr0[2] + inptr1[-1] + inptr1[2];

      /* The edge-neighbors count twice as much as corner-neighbors */

      neighsum += neighsum;

      /* Add in the corner-neighbors */

      neighsum += above_ptr[-1] + above_ptr[2] + below_ptr[-1] + below_ptr[2];

      /* form final output scaled up by 2^16 */

      membersum = membersum * memberscale + neighsum * neighscale;

      /* round, descale and output it */

      *outptr++ = (_JSAMPLE)((membersum + 32768) >> 16);

      inptr0 += 2;  inptr1 += 2;  above_ptr += 2;  below_ptr += 2;

    }

    /* Special case for last column */

    membersum = inptr0[0] + inptr0[1] + inptr1[0] + inptr1[1];

    neighsum = above_ptr[0] + above_ptr[1] + below_ptr[0] + below_ptr[1] +

               inptr0[-1] + inptr0[1] + inptr1[-1] + inptr1[1];

    neighsum += neighsum;

    neighsum += above_ptr[-1] + above_ptr[1] + below_ptr[-1] + below_ptr[1];

    membersum = membersum * memberscale + neighsum * neighscale;

    *outptr = (_JSAMPLE)((membersum + 32768) >> 16);

    inrow += 2;

  }

}

/*

 * Downsample pixel values of a single component.

 * This version handles the special case of a full-size component,

 * with smoothing.  One row of context is required.

 */

METHODDEF(void)

fullsize_smooth_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,

                           _JSAMPARRAY input_data, _JSAMPARRAY output_data)

{

  int outrow;

  JDIMENSION colctr;

  int data_unit = cinfo->master->lossless ? 1 : DCTSIZE;

  JDIMENSION output_cols = compptr->width_in_blocks * data_unit;

  register _JSAMPROW inptr, above_ptr, below_ptr, outptr;

  JLONG membersum, neighsum, memberscale, neighscale;

  int colsum, lastcolsum, nextcolsum;

  /* Expand input data enough to let all the output samples be generated

   * by the standard loop.  Special-casing padded output would be more

   * efficient.

   */

  expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,

                    cinfo->image_width, output_cols);

  /* Each of the eight neighbor pixels contributes a fraction SF to the

   * smoothed pixel, while the main pixel contributes (1-8*SF).  In order

   * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.

   * Also recall that SF = smoothing_factor / 1024.

   */

  memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */

  neighscale = cinfo->smoothing_factor * 64; /* scaled SF */

  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {

    outptr = output_data[outrow];

    inptr = input_data[outrow];

    above_ptr = input_data[outrow - 1];

    below_ptr = input_data[outrow + 1];

    /* Special case for first column */

    colsum = (*above_ptr++) + (*below_ptr++) + inptr[0];

    membersum = *inptr++;

    nextcolsum = above_ptr[0] + below_ptr[0] + inptr[0];

    neighsum = colsum + (colsum - membersum) + nextcolsum;

    membersum = membersum * memberscale + neighsum * neighscale;

    *outptr++ = (_JSAMPLE)((membersum + 32768) >> 16);

    lastcolsum = colsum;  colsum = nextcolsum;

    for (colctr = output_cols - 2; colctr > 0; colctr--) {

      membersum = *inptr++;

      above_ptr++;  below_ptr++;

      nextcolsum = above_ptr[0] + below_ptr[0] + inptr[0];

      neighsum = lastcolsum + (colsum - membersum) + nextcolsum;

      membersum = membersum * memberscale + neighsum * neighscale;

      *outptr++ = (_JSAMPLE)((membersum + 32768) >> 16);

      lastcolsum = colsum;  colsum = nextcolsum;

    }

    /* Special case for last column */

    membersum = *inptr;

    neighsum = lastcolsum + (colsum - membersum) + colsum;

    membersum = membersum * memberscale + neighsum * neighscale;

    *outptr = (_JSAMPLE)((membersum + 32768) >> 16);

  }

}

#endif /* INPUT_SMOOTHING_SUPPORTED */

/*

 * Module initialization routine for downsampling.

 * Note that we must select a routine for each component.

 */

GLOBAL(void)

_jinit_downsampler(j_compress_ptr cinfo)

{

  my_downsample_ptr downsample;

  int ci;

  jpeg_component_info *compptr;

  boolean smoothok = TRUE;

  if (cinfo->data_precision != BITS_IN_JSAMPLE)

    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);

  downsample = (my_downsample_ptr)

    (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,

                                sizeof(my_downsampler));

  cinfo->downsample = (struct jpeg_downsampler *)downsample;

  downsample->pub.start_pass = start_pass_downsample;

  downsample->pub._downsample = sep_downsample;

  downsample->pub.need_context_rows = FALSE;

  if (cinfo->CCIR601_sampling)

    ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

  /* Verify we can handle the sampling factors, and set up method pointers */

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&

        compptr->v_samp_factor == cinfo->max_v_samp_factor) {

#ifdef INPUT_SMOOTHING_SUPPORTED

      if (cinfo->smoothing_factor) {

        downsample->methods[ci] = fullsize_smooth_downsample;

        downsample->pub.need_context_rows = TRUE;

      } else

#endif

        downsample->methods[ci] = fullsize_downsample;

    } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&

               compptr->v_samp_factor == cinfo->max_v_samp_factor) {

      smoothok = FALSE;

#ifdef WITH_SIMD

      if (jsimd_can_h2v1_downsample())

        downsample->methods[ci] = jsimd_h2v1_downsample;

      else

#endif

        downsample->methods[ci] = h2v1_downsample;

    } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&

               compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) {

#ifdef INPUT_SMOOTHING_SUPPORTED

      if (cinfo->smoothing_factor) {

#if defined(WITH_SIMD) && defined(__mips__)

        if (jsimd_can_h2v2_smooth_downsample())

          downsample->methods[ci] = jsimd_h2v2_smooth_downsample;

        else

#endif

          downsample->methods[ci] = h2v2_smooth_downsample;

        downsample->pub.need_context_rows = TRUE;

      } else

#endif

      {

#ifdef WITH_SIMD

        if (jsimd_can_h2v2_downsample())

          downsample->methods[ci] = jsimd_h2v2_downsample;

        else

#endif

          downsample->methods[ci] = h2v2_downsample;

      }

    } else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&

               (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) {

      smoothok = FALSE;

      downsample->methods[ci] = int_downsample;

    } else

      ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);

  }

#ifdef INPUT_SMOOTHING_SUPPORTED

  if (cinfo->smoothing_factor && !smoothok)

    TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL);

#endif

}

Unexecuted instantiation: jinit_downsampler

Unexecuted instantiation: j12init_downsampler

Unexecuted instantiation: j16init_downsampler

#endif /* BITS_IN_JSAMPLE != 16 || defined(C_LOSSLESS_SUPPORTED) */