/*

 * DirectDraw Surface image decoder

 * Copyright (C) 2015 Vittorio Giovara <vittorio.giovara@gmail.com>

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

/**

 * @file

 * DDS decoder

 *

 * https://msdn.microsoft.com/en-us/library/bb943982%28v=vs.85%29.aspx

 */

#include <math.h>

#include <stdint.h>

#include "libavutil/attributes.h"

#include "libavutil/imgutils.h"

#include "avcodec.h"

#include "bytestream.h"

#include "codec_internal.h"

#include "decode.h"

#include "texturedsp.h"

#define DDPF_FOURCC    (1 <<  2)

#define DDPF_PALETTE   (1 <<  5)

#define DDPF_NORMALMAP (1U << 31)

enum DDSPostProc {

    DDS_NONE = 0,

    DDS_ALPHA_EXP,

    DDS_NORMAL_MAP,

    DDS_RAW_YCOCG,

    DDS_SWAP_ALPHA,

    DDS_SWIZZLE_A2XY,

    DDS_SWIZZLE_RBXG,

    DDS_SWIZZLE_RGXB,

    DDS_SWIZZLE_RXBG,

    DDS_SWIZZLE_RXGB,

    DDS_SWIZZLE_XGBR,

    DDS_SWIZZLE_XRBG,

    DDS_SWIZZLE_XGXR,

};

enum DDSDXGIFormat {

    DXGI_FORMAT_R16G16B16A16_TYPELESS       =  9,

    DXGI_FORMAT_R16G16B16A16_FLOAT          = 10,

    DXGI_FORMAT_R16G16B16A16_UNORM          = 11,

    DXGI_FORMAT_R16G16B16A16_UINT           = 12,

    DXGI_FORMAT_R16G16B16A16_SNORM          = 13,

    DXGI_FORMAT_R16G16B16A16_SINT           = 14,

    DXGI_FORMAT_R8G8B8A8_TYPELESS           = 27,

    DXGI_FORMAT_R8G8B8A8_UNORM              = 28,

    DXGI_FORMAT_R8G8B8A8_UNORM_SRGB         = 29,

    DXGI_FORMAT_R8G8B8A8_UINT               = 30,

    DXGI_FORMAT_R8G8B8A8_SNORM              = 31,

    DXGI_FORMAT_R8G8B8A8_SINT               = 32,

    DXGI_FORMAT_BC1_TYPELESS                = 70,

    DXGI_FORMAT_BC1_UNORM                   = 71,

    DXGI_FORMAT_BC1_UNORM_SRGB              = 72,

    DXGI_FORMAT_BC2_TYPELESS                = 73,

    DXGI_FORMAT_BC2_UNORM                   = 74,

    DXGI_FORMAT_BC2_UNORM_SRGB              = 75,

    DXGI_FORMAT_BC3_TYPELESS                = 76,

    DXGI_FORMAT_BC3_UNORM                   = 77,

    DXGI_FORMAT_BC3_UNORM_SRGB              = 78,

    DXGI_FORMAT_BC4_TYPELESS                = 79,

    DXGI_FORMAT_BC4_UNORM                   = 80,

    DXGI_FORMAT_BC4_SNORM                   = 81,

    DXGI_FORMAT_BC5_TYPELESS                = 82,

    DXGI_FORMAT_BC5_UNORM                   = 83,

    DXGI_FORMAT_BC5_SNORM                   = 84,

    DXGI_FORMAT_B5G6R5_UNORM                = 85,

    DXGI_FORMAT_B8G8R8A8_UNORM              = 87,

    DXGI_FORMAT_B8G8R8X8_UNORM              = 88,

    DXGI_FORMAT_B8G8R8A8_TYPELESS           = 90,

    DXGI_FORMAT_B8G8R8A8_UNORM_SRGB         = 91,

    DXGI_FORMAT_B8G8R8X8_TYPELESS           = 92,

    DXGI_FORMAT_B8G8R8X8_UNORM_SRGB         = 93,

};

typedef struct DDSContext {

    TextureDSPContext texdsp;

    GetByteContext gbc;

    int compressed;

    int paletted;

    int bpp;

    enum DDSPostProc postproc;

    TextureDSPThreadContext dec;

} DDSContext;

static int parse_pixel_format(AVCodecContext *avctx)

{

    DDSContext *ctx = avctx->priv_data;

    GetByteContext *gbc = &ctx->gbc;

    uint32_t flags, fourcc, gimp_tag;

    enum DDSDXGIFormat dxgi;

    int size, bpp, r, g, b, a;

    int alpha_exponent, ycocg_classic, ycocg_scaled, normal_map, array;

    /* Alternative DDS implementations use reserved1 as custom header. */

    bytestream2_skip(gbc, 4 * 3);

    gimp_tag = bytestream2_get_le32(gbc);

    alpha_exponent = gimp_tag == MKTAG('A', 'E', 'X', 'P');

    ycocg_classic  = gimp_tag == MKTAG('Y', 'C', 'G', '1');

    ycocg_scaled   = gimp_tag == MKTAG('Y', 'C', 'G', '2');

    bytestream2_skip(gbc, 4 * 7);

    /* Now the real DDPF starts. */

    size = bytestream2_get_le32(gbc);

    if (size != 32) {

        av_log(avctx, AV_LOG_ERROR, "Invalid pixel format header %d.\n", size);

        return AVERROR_INVALIDDATA;

    }

    flags = bytestream2_get_le32(gbc);

    ctx->compressed = flags & DDPF_FOURCC;

    ctx->paletted   = flags & DDPF_PALETTE;

    normal_map      = flags & DDPF_NORMALMAP;

    fourcc = bytestream2_get_le32(gbc);

    if (ctx->compressed && ctx->paletted) {

        av_log(avctx, AV_LOG_WARNING,

               "Disabling invalid palette flag for compressed dds.\n");

        ctx->paletted = 0;

    }

    bpp = ctx->bpp = bytestream2_get_le32(gbc); // rgbbitcount

    r   = bytestream2_get_le32(gbc); // rbitmask

    g   = bytestream2_get_le32(gbc); // gbitmask

    b   = bytestream2_get_le32(gbc); // bbitmask

    a   = bytestream2_get_le32(gbc); // abitmask

    bytestream2_skip(gbc, 4); // caps

    bytestream2_skip(gbc, 4); // caps2

    bytestream2_skip(gbc, 4); // caps3

    bytestream2_skip(gbc, 4); // caps4

    bytestream2_skip(gbc, 4); // reserved2

    av_log(avctx, AV_LOG_VERBOSE, "fourcc %s bpp %d "

           "r 0x%x g 0x%x b 0x%x a 0x%x\n", av_fourcc2str(fourcc), bpp, r, g, b, a);

    if (gimp_tag)

        av_log(avctx, AV_LOG_VERBOSE, "and GIMP-DDS tag %s\n", av_fourcc2str(gimp_tag));

    if (ctx->compressed)

        avctx->pix_fmt = AV_PIX_FMT_RGBA;

    if (ctx->compressed) {

        ctx->dec.raw_ratio = 16;

        switch (fourcc) {

        case MKTAG('D', 'X', 'T', '1'):

            ctx->dec.tex_ratio = 8;

            ctx->dec.tex_funct = ctx->texdsp.dxt1a_block;

            break;

        case MKTAG('D', 'X', 'T', '2'):

            ctx->dec.tex_ratio = 16;

            ctx->dec.tex_funct = ctx->texdsp.dxt2_block;

            break;

        case MKTAG('D', 'X', 'T', '3'):

            ctx->dec.tex_ratio = 16;

            ctx->dec.tex_funct = ctx->texdsp.dxt3_block;

            break;

        case MKTAG('D', 'X', 'T', '4'):

            ctx->dec.tex_ratio = 16;

            ctx->dec.tex_funct = ctx->texdsp.dxt4_block;

            break;

        case MKTAG('D', 'X', 'T', '5'):

            ctx->dec.tex_ratio = 16;

            if (ycocg_scaled)

                ctx->dec.tex_funct = ctx->texdsp.dxt5ys_block;

            else if (ycocg_classic)

                ctx->dec.tex_funct = ctx->texdsp.dxt5y_block;

            else

                ctx->dec.tex_funct = ctx->texdsp.dxt5_block;

            break;

        case MKTAG('R', 'X', 'G', 'B'):

            ctx->dec.tex_ratio = 16;

            ctx->dec.tex_funct = ctx->texdsp.dxt5_block;

            /* This format may be considered as a normal map,

             * but it is handled differently in a separate postproc. */

            ctx->postproc = DDS_SWIZZLE_RXGB;

            normal_map = 0;

            break;

        case MKTAG('A', 'T', 'I', '1'):

        case MKTAG('B', 'C', '4', 'U'):

            ctx->dec.tex_ratio = 8;

            ctx->dec.tex_funct = ctx->texdsp.rgtc1u_block;

            break;

        case MKTAG('B', 'C', '4', 'S'):

            ctx->dec.tex_ratio = 8;

            ctx->dec.tex_funct = ctx->texdsp.rgtc1s_block;

            break;

        case MKTAG('A', 'T', 'I', '2'):

            /* RGT2 variant with swapped R and G (3Dc)*/

            ctx->dec.tex_ratio = 16;

            ctx->dec.tex_funct = ctx->texdsp.dxn3dc_block;

            break;

        case MKTAG('B', 'C', '5', 'U'):

            ctx->dec.tex_ratio = 16;

            ctx->dec.tex_funct = ctx->texdsp.rgtc2u_block;

            break;

        case MKTAG('B', 'C', '5', 'S'):

            ctx->dec.tex_ratio = 16;

            ctx->dec.tex_funct = ctx->texdsp.rgtc2s_block;

            break;

        case MKTAG('U', 'Y', 'V', 'Y'):

            ctx->compressed = 0;

            avctx->pix_fmt = AV_PIX_FMT_UYVY422;

            break;

        case MKTAG('Y', 'U', 'Y', '2'):

            ctx->compressed = 0;

            avctx->pix_fmt = AV_PIX_FMT_YUYV422;

            break;

        case MKTAG('P', '8', ' ', ' '):

            /* ATI Palette8, same as normal palette */

            ctx->compressed = 0;

            ctx->paletted   = 1;

            avctx->pix_fmt  = AV_PIX_FMT_PAL8;

            break;

        case MKTAG('G', '1', ' ', ' '):

            ctx->compressed = 0;

            avctx->pix_fmt  = AV_PIX_FMT_MONOBLACK;

            break;

        case MKTAG('D', 'X', '1', '0'):

            /* DirectX 10 extra header */

            dxgi = bytestream2_get_le32(gbc);

            bytestream2_skip(gbc, 4); // resourceDimension

            bytestream2_skip(gbc, 4); // miscFlag

            array = bytestream2_get_le32(gbc);

            bytestream2_skip(gbc, 4); // miscFlag2

            if (array != 0)

                av_log(avctx, AV_LOG_VERBOSE,

                       "Found array of size %d (ignored).\n", array);

            /* Only BC[1-5] are actually compressed. */

            ctx->compressed = (dxgi >= 70) && (dxgi <= 84);

            av_log(avctx, AV_LOG_VERBOSE, "DXGI format %d.\n", dxgi);

            switch (dxgi) {

            /* RGB types. */

            case DXGI_FORMAT_R16G16B16A16_TYPELESS:

            case DXGI_FORMAT_R16G16B16A16_FLOAT:

            case DXGI_FORMAT_R16G16B16A16_UNORM:

            case DXGI_FORMAT_R16G16B16A16_UINT:

            case DXGI_FORMAT_R16G16B16A16_SNORM:

            case DXGI_FORMAT_R16G16B16A16_SINT:

                avctx->pix_fmt = AV_PIX_FMT_BGRA64;

                break;

            case DXGI_FORMAT_R8G8B8A8_UNORM_SRGB:

                avctx->colorspace = AVCOL_SPC_RGB;

                av_fallthrough;

            case DXGI_FORMAT_R8G8B8A8_TYPELESS:

            case DXGI_FORMAT_R8G8B8A8_UNORM:

            case DXGI_FORMAT_R8G8B8A8_UINT:

            case DXGI_FORMAT_R8G8B8A8_SNORM:

            case DXGI_FORMAT_R8G8B8A8_SINT:

                avctx->pix_fmt = AV_PIX_FMT_BGRA;

                break;

            case DXGI_FORMAT_B8G8R8A8_UNORM_SRGB:

                avctx->colorspace = AVCOL_SPC_RGB;

                av_fallthrough;

            case DXGI_FORMAT_B8G8R8A8_TYPELESS:

            case DXGI_FORMAT_B8G8R8A8_UNORM:

                avctx->pix_fmt = AV_PIX_FMT_RGBA;

                break;

            case DXGI_FORMAT_B8G8R8X8_UNORM_SRGB:

                avctx->colorspace = AVCOL_SPC_RGB;

                av_fallthrough;

            case DXGI_FORMAT_B8G8R8X8_TYPELESS:

            case DXGI_FORMAT_B8G8R8X8_UNORM:

                avctx->pix_fmt = AV_PIX_FMT_RGBA; // opaque

                break;

            case DXGI_FORMAT_B5G6R5_UNORM:

                avctx->pix_fmt = AV_PIX_FMT_RGB565LE;

                break;

            /* Texture types. */

            case DXGI_FORMAT_BC1_UNORM_SRGB:

                avctx->colorspace = AVCOL_SPC_RGB;

                av_fallthrough;

            case DXGI_FORMAT_BC1_TYPELESS:

            case DXGI_FORMAT_BC1_UNORM:

                ctx->dec.tex_ratio = 8;

                ctx->dec.tex_funct = ctx->texdsp.dxt1a_block;

                break;

            case DXGI_FORMAT_BC2_UNORM_SRGB:

                avctx->colorspace = AVCOL_SPC_RGB;

                av_fallthrough;

            case DXGI_FORMAT_BC2_TYPELESS:

            case DXGI_FORMAT_BC2_UNORM:

                ctx->dec.tex_ratio = 16;

                ctx->dec.tex_funct = ctx->texdsp.dxt3_block;

                break;

            case DXGI_FORMAT_BC3_UNORM_SRGB:

                avctx->colorspace = AVCOL_SPC_RGB;

                av_fallthrough;

            case DXGI_FORMAT_BC3_TYPELESS:

            case DXGI_FORMAT_BC3_UNORM:

                ctx->dec.tex_ratio = 16;

                ctx->dec.tex_funct = ctx->texdsp.dxt5_block;

                break;

            case DXGI_FORMAT_BC4_TYPELESS:

            case DXGI_FORMAT_BC4_UNORM:

                ctx->dec.tex_ratio = 8;

                ctx->dec.tex_funct = ctx->texdsp.rgtc1u_block;

                break;

            case DXGI_FORMAT_BC4_SNORM:

                ctx->dec.tex_ratio = 8;

                ctx->dec.tex_funct = ctx->texdsp.rgtc1s_block;

                break;

            case DXGI_FORMAT_BC5_TYPELESS:

            case DXGI_FORMAT_BC5_UNORM:

                ctx->dec.tex_ratio = 16;

                ctx->dec.tex_funct = ctx->texdsp.rgtc2u_block;

                break;

            case DXGI_FORMAT_BC5_SNORM:

                ctx->dec.tex_ratio = 16;

                ctx->dec.tex_funct = ctx->texdsp.rgtc2s_block;

                break;

            default:

                av_log(avctx, AV_LOG_ERROR,

                       "Unsupported DXGI format %d.\n", dxgi);

                return AVERROR_INVALIDDATA;

            }

            break;

        default:

            av_log(avctx, AV_LOG_ERROR, "Unsupported %s fourcc.\n", av_fourcc2str(fourcc));

            return AVERROR_INVALIDDATA;

        }

    } else if (ctx->paletted) {

        if (bpp == 8) {

            avctx->pix_fmt = AV_PIX_FMT_PAL8;

        } else {

            av_log(avctx, AV_LOG_ERROR, "Unsupported palette bpp %d.\n", bpp);

            return AVERROR_INVALIDDATA;

        }

    } else {

        /*  4 bpp */

        if (bpp == 4 && r == 0 && g == 0 && b == 0 && a == 0)

            avctx->pix_fmt = AV_PIX_FMT_PAL8;

        /*  8 bpp */

        else if (bpp == 8 && r == 0xff && g == 0 && b == 0 && a == 0)

            avctx->pix_fmt = AV_PIX_FMT_GRAY8;

        else if (bpp == 8 && r == 0 && g == 0 && b == 0 && a == 0xff)

            avctx->pix_fmt = AV_PIX_FMT_GRAY8;

        /* 16 bpp */

        else if (bpp == 16 && r == 0xff && g == 0 && b == 0 && a == 0xff00)

            avctx->pix_fmt = AV_PIX_FMT_YA8;

        else if (bpp == 16 && r == 0xff00 && g == 0 && b == 0 && a == 0xff) {

            avctx->pix_fmt = AV_PIX_FMT_YA8;

            ctx->postproc = DDS_SWAP_ALPHA;

        }

        else if (bpp == 16 && r == 0xffff && g == 0 && b == 0 && a == 0)

            avctx->pix_fmt = AV_PIX_FMT_GRAY16LE;

        else if (bpp == 16 && r == 0x7c00 && g == 0x3e0 && b == 0x1f && a == 0)

            avctx->pix_fmt = AV_PIX_FMT_RGB555LE;

        else if (bpp == 16 && r == 0x7c00 && g == 0x3e0 && b == 0x1f && a == 0x8000)

            avctx->pix_fmt = AV_PIX_FMT_RGB555LE; // alpha ignored

        else if (bpp == 16 && r == 0xf800 && g == 0x7e0 && b == 0x1f && a == 0)

            avctx->pix_fmt = AV_PIX_FMT_RGB565LE;

        /* 24 bpp */

        else if (bpp == 24 && r == 0xff0000 && g == 0xff00 && b == 0xff && a == 0)

            avctx->pix_fmt = AV_PIX_FMT_BGR24;

        /* 32 bpp */

        else if (bpp == 32 && r == 0xff0000 && g == 0xff00 && b == 0xff && a == 0)

            avctx->pix_fmt = AV_PIX_FMT_BGR0; // opaque

        else if (bpp == 32 && r == 0xff && g == 0xff00 && b == 0xff0000 && a == 0)

            avctx->pix_fmt = AV_PIX_FMT_RGB0; // opaque

        else if (bpp == 32 && r == 0xff0000 && g == 0xff00 && b == 0xff && a == 0xff000000)

            avctx->pix_fmt = AV_PIX_FMT_BGRA;

        else if (bpp == 32 && r == 0xff && g == 0xff00 && b == 0xff0000 && a == 0xff000000)

            avctx->pix_fmt = AV_PIX_FMT_RGBA;

        /* give up */

        else {

            av_log(avctx, AV_LOG_ERROR, "Unknown pixel format "

                   "[bpp %d r 0x%x g 0x%x b 0x%x a 0x%x].\n", bpp, r, g, b, a);

            return AVERROR_INVALIDDATA;

        }

    }

    /* Set any remaining post-proc that should happen before frame is ready. */

    if (alpha_exponent)

        ctx->postproc = DDS_ALPHA_EXP;

    else if (normal_map)

        ctx->postproc = DDS_NORMAL_MAP;

    else if (ycocg_classic && !ctx->compressed)

        ctx->postproc = DDS_RAW_YCOCG;

    /* ATI/NVidia variants sometimes add swizzling in bpp. */

    switch (bpp) {

    case MKTAG('A', '2', 'X', 'Y'):

        ctx->postproc = DDS_SWIZZLE_A2XY;

        break;

    case MKTAG('x', 'G', 'B', 'R'):

        ctx->postproc = DDS_SWIZZLE_XGBR;

        break;

    case MKTAG('x', 'R', 'B', 'G'):

        ctx->postproc = DDS_SWIZZLE_XRBG;

        break;

    case MKTAG('R', 'B', 'x', 'G'):

        ctx->postproc = DDS_SWIZZLE_RBXG;

        break;

    case MKTAG('R', 'G', 'x', 'B'):

        ctx->postproc = DDS_SWIZZLE_RGXB;

        break;

    case MKTAG('R', 'x', 'B', 'G'):

        ctx->postproc = DDS_SWIZZLE_RXBG;

        break;

    case MKTAG('x', 'G', 'x', 'R'):

        ctx->postproc = DDS_SWIZZLE_XGXR;

        break;

    case MKTAG('A', '2', 'D', '5'):

        ctx->postproc = DDS_NORMAL_MAP;

        break;

    }

    return 0;

}

static void do_swizzle(AVFrame *frame, int x, int y)

{

    int i;

    for (i = 0; i < frame->linesize[0] * frame->height; i += 4) {

        uint8_t *src = frame->data[0] + i;

        FFSWAP(uint8_t, src[x], src[y]);

    }

}

static void run_postproc(AVCodecContext *avctx, AVFrame *frame)

{

    DDSContext *ctx = avctx->priv_data;

    int i, x_off;

    switch (ctx->postproc) {

    case DDS_ALPHA_EXP:

        /* Alpha-exponential mode divides each channel by the maximum

         * R, G or B value, and stores the multiplying factor in the

         * alpha channel. */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing alpha exponent.\n");

        for (i = 0; i < frame->linesize[0] * frame->height; i += 4) {

            uint8_t *src = frame->data[0] + i;

            int r = src[0];

            int g = src[1];

            int b = src[2];

            int a = src[3];

            src[0] = r * a / 255;

            src[1] = g * a / 255;

            src[2] = b * a / 255;

            src[3] = 255;

        }

        break;

    case DDS_NORMAL_MAP:

        /* Normal maps work in the XYZ color space and they encode

         * X in R or in A, depending on the texture type, Y in G and

         * derive Z with a square root of the distance.

         *

         * http://www.realtimecollisiondetection.net/blog/?p=28 */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing normal map.\n");

        x_off = ctx->dec.tex_ratio == 8 ? 0 : 3;

        for (i = 0; i < frame->linesize[0] * frame->height; i += 4) {

            uint8_t *src = frame->data[0] + i;

            int x = src[x_off];

            int y = src[1];

            int z = 127;

            int d = (255 * 255 - x * x - y * y) / 2;

            if (d > 0)

                z = lrint(sqrtf(d));

            src[0] = x;

            src[1] = y;

            src[2] = z;

            src[3] = 255;

        }

        break;

    case DDS_RAW_YCOCG:

        /* Data is Y-Co-Cg-A and not RGBA, but they are represented

         * with the same masks in the DDPF header. */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing raw YCoCg.\n");

        for (i = 0; i < frame->linesize[0] * frame->height; i += 4) {

            uint8_t *src = frame->data[0] + i;

            int a  = src[0];

            int cg = src[1] - 128;

            int co = src[2] - 128;

            int y  = src[3];

            src[0] = av_clip_uint8(y + co - cg);

            src[1] = av_clip_uint8(y + cg);

            src[2] = av_clip_uint8(y - co - cg);

            src[3] = a;

        }

        break;

    case DDS_SWAP_ALPHA:

        /* Alpha and Luma are stored swapped. */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing swapped Luma/Alpha.\n");

        for (i = 0; i < frame->linesize[0] * frame->height; i += 2) {

            uint8_t *src = frame->data[0] + i;

            FFSWAP(uint8_t, src[0], src[1]);

        }

        break;

    case DDS_SWIZZLE_A2XY:

        /* Swap R and G, often used to restore a standard RGTC2. */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing A2XY swizzle.\n");

        do_swizzle(frame, 0, 1);

        break;

    case DDS_SWIZZLE_RBXG:

        /* Swap G and A, then B and new A (G). */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing RBXG swizzle.\n");

        do_swizzle(frame, 1, 3);

        do_swizzle(frame, 2, 3);

        break;

    case DDS_SWIZZLE_RGXB:

        /* Swap B and A. */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing RGXB swizzle.\n");

        do_swizzle(frame, 2, 3);

        break;

    case DDS_SWIZZLE_RXBG:

        /* Swap G and A. */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing RXBG swizzle.\n");

        do_swizzle(frame, 1, 3);

        break;

    case DDS_SWIZZLE_RXGB:

        /* Swap R and A (misleading name). */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing RXGB swizzle.\n");

        do_swizzle(frame, 0, 3);

        break;

    case DDS_SWIZZLE_XGBR:

        /* Swap B and A, then R and new A (B). */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing XGBR swizzle.\n");

        do_swizzle(frame, 2, 3);

        do_swizzle(frame, 0, 3);

        break;

    case DDS_SWIZZLE_XGXR:

        /* Swap G and A, then R and new A (G), then new R (G) and new G (A).

         * This variant does not store any B component. */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing XGXR swizzle.\n");

        do_swizzle(frame, 1, 3);

        do_swizzle(frame, 0, 3);

        do_swizzle(frame, 0, 1);

        break;

    case DDS_SWIZZLE_XRBG:

        /* Swap G and A, then R and new A (G). */

        av_log(avctx, AV_LOG_DEBUG, "Post-processing XRBG swizzle.\n");

        do_swizzle(frame, 1, 3);

        do_swizzle(frame, 0, 3);

        break;

    }

}

static int dds_decode(AVCodecContext *avctx, AVFrame *frame,

                      int *got_frame, AVPacket *avpkt)

{

    DDSContext *ctx = avctx->priv_data;

    GetByteContext *gbc = &ctx->gbc;

    int mipmap;

    int ret;

    int width, height;

    ff_texturedsp_init(&ctx->texdsp);

    bytestream2_init(gbc, avpkt->data, avpkt->size);

    if (bytestream2_get_bytes_left(gbc) < 128) {

        av_log(avctx, AV_LOG_ERROR, "Frame is too small (%d).\n",

               bytestream2_get_bytes_left(gbc));

        return AVERROR_INVALIDDATA;

    }

    if (bytestream2_get_le32(gbc) != MKTAG('D', 'D', 'S', ' ') ||

        bytestream2_get_le32(gbc) != 124) { // header size

        av_log(avctx, AV_LOG_ERROR, "Invalid DDS header.\n");

        return AVERROR_INVALIDDATA;

    }

    bytestream2_skip(gbc, 4); // flags

    height = bytestream2_get_le32(gbc);

    width  = bytestream2_get_le32(gbc);

    ret = ff_set_dimensions(avctx, width, height);

    if (ret < 0) {

        av_log(avctx, AV_LOG_ERROR, "Invalid image size %dx%d.\n",

               avctx->width, avctx->height);

        return ret;

    }

    /* Since codec is based on 4x4 blocks, size is aligned to 4. */

    avctx->coded_width  = FFALIGN(avctx->width,  TEXTURE_BLOCK_W);

    avctx->coded_height = FFALIGN(avctx->height, TEXTURE_BLOCK_H);

    bytestream2_skip(gbc, 4); // pitch

    bytestream2_skip(gbc, 4); // depth

    mipmap = bytestream2_get_le32(gbc);

    if (mipmap != 0)

        av_log(avctx, AV_LOG_VERBOSE, "Found %d mipmaps (ignored).\n", mipmap);

    /* Extract pixel format information, considering additional elements

     * in reserved1 and reserved2. */

    ret = parse_pixel_format(avctx);

    if (ret < 0)

        return ret;

    ret = ff_get_buffer(avctx, frame, 0);

    if (ret < 0)

        return ret;

    if (ctx->compressed) {

        int size = (avctx->coded_height / TEXTURE_BLOCK_H) *

                   (avctx->coded_width / TEXTURE_BLOCK_W) * ctx->dec.tex_ratio;

        ctx->dec.slice_count = av_clip(avctx->thread_count, 1,

                                       avctx->coded_height / TEXTURE_BLOCK_H);

        if (bytestream2_get_bytes_left(gbc) < size) {

            av_log(avctx, AV_LOG_ERROR,

                   "Compressed Buffer is too small (%d < %d).\n",

                   bytestream2_get_bytes_left(gbc), size);

            return AVERROR_INVALIDDATA;

        }

        /* Use the decompress function on the texture, one block per thread. */

        ctx->dec.tex_data.in = gbc->buffer;

        ctx->dec.frame_data.out = frame->data[0];

        ctx->dec.stride = frame->linesize[0];

        ctx->dec.width  = avctx->coded_width;

        ctx->dec.height = avctx->coded_height;

        ff_texturedsp_exec_decompress_threads(avctx, &ctx->dec);

    } else if (!ctx->paletted && ctx->bpp == 4 && avctx->pix_fmt == AV_PIX_FMT_PAL8) {

        uint8_t *dst = frame->data[0];

        int x, y, i;

        /* Use the first 64 bytes as palette, then copy the rest. */

        bytestream2_get_buffer(gbc, frame->data[1], 16 * 4);

        for (i = 0; i < 16; i++) {

            AV_WN32(frame->data[1] + i*4,

                    (frame->data[1][2+i*4]<<0)+

                    (frame->data[1][1+i*4]<<8)+

                    (frame->data[1][0+i*4]<<16)+

                    ((unsigned)frame->data[1][3+i*4]<<24)

            );

        }

        if (bytestream2_get_bytes_left(gbc) < frame->height * frame->width / 2) {

            av_log(avctx, AV_LOG_ERROR, "Buffer is too small (%d < %d).\n",

                   bytestream2_get_bytes_left(gbc), frame->height * frame->width / 2);

            return AVERROR_INVALIDDATA;

        }

        for (y = 0; y < frame->height; y++) {

            for (x = 0; x < frame->width; x += 2) {

                uint8_t val = bytestream2_get_byte(gbc);

                dst[x    ] = val & 0xF;

                dst[x + 1] = val >> 4;

            }

            dst += frame->linesize[0];

        }

    } else {

        int linesize = av_image_get_linesize(avctx->pix_fmt, frame->width, 0);

        if (ctx->paletted) {

            int i;

            /* Use the first 1024 bytes as palette, then copy the rest. */

            bytestream2_get_buffer(gbc, frame->data[1], 256 * 4);

            for (i = 0; i < 256; i++)

                AV_WN32(frame->data[1] + i*4,

                        (frame->data[1][2+i*4]<<0)+

                        (frame->data[1][1+i*4]<<8)+

                        (frame->data[1][0+i*4]<<16)+

                        ((unsigned)frame->data[1][3+i*4]<<24)

                );

        }

        if (bytestream2_get_bytes_left(gbc) < frame->height * linesize) {

            av_log(avctx, AV_LOG_ERROR, "Buffer is too small (%d < %d).\n",

                   bytestream2_get_bytes_left(gbc), frame->height * linesize);

            return AVERROR_INVALIDDATA;

        }

        av_image_copy_plane(frame->data[0], frame->linesize[0],

                            gbc->buffer, linesize,

                            linesize, frame->height);

    }

    /* Run any post processing here if needed. */

    if (ctx->postproc != DDS_NONE)

        run_postproc(avctx, frame);

    /* Frame is ready to be output. */

    *got_frame = 1;

    return avpkt->size;

}

const FFCodec ff_dds_decoder = {

    .p.name         = "dds",

    CODEC_LONG_NAME("DirectDraw Surface image decoder"),

    .p.type         = AVMEDIA_TYPE_VIDEO,

    .p.id           = AV_CODEC_ID_DDS,

    FF_CODEC_DECODE_CB(dds_decode),

    .priv_data_size = sizeof(DDSContext),

    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_SLICE_THREADS,

};