kc3-lang/angle/src/image_util/loadimage_paletted.cpp

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• Hash : ff7aa214
  Author :
  Date : 2022-09-29T19:56:28
  

  GL_PALETTE* sampling
  
  Implement GL_PALETTE* formats by decoding them into
  a R8G8B8A8_UNORM image at load time.
  
  Test: angle_end2end_tests --gtest_filter="PalettedTextureTest.*"
  Bug: angleproject:7599
  Bug: angleproject:7688
  Bug: angleproject:7710
  Change-Id: I94d51e2c480fcdd39f1a0ad241b311d3b4de1579
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3863251
  Reviewed-by: Cody Northrop <cnorthrop@google.com>
  Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
  Commit-Queue: Constantine Shablya <constantine.shablya@collabora.com>
  

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• src/image_util/loadimage_paletted.cpp

• //
  // Copyright 2022 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  
  // loadimage_paletted.cpp: Decodes GL_PALETTE_* textures.
  
  #include "image_util/loadimage.h"
  
  #include <type_traits>
  #include "common/mathutil.h"
  
  #include "image_util/imageformats.h"
  
  namespace angle
  {
  
  namespace
  {
  
  template <typename T>
  R8G8B8A8 ReadColor(const T *src)
  {
      gl::ColorF tmp;
      T::readColor(&tmp, src);
      R8G8B8A8 rgba;
      R8G8B8A8::writeColor(&rgba, &tmp);
      return rgba;
  }
  
  size_t DecodeIndexIntoPalette(const uint8_t *row, size_t i, uint32_t indexBits)
  {
      switch (indexBits)
      {
          case 4:
          {
              // From OES_compressed_paletted_texture, section Additions to
              // Chapter 3 of the OpenGL 1.3 Specification (Rasterization):
              //
              // Texel Data Formats for compressed paletted textures
              //
              // PALETTE4_xxx:
              //
              //      7 6 5 4 3 2 1 0
              //      ---------------
              //     |  1st  |  2nd  |
              //     | texel | texel |
              //      ---------------
  
              bool even = i % 2 == 0;
              return (row[i / 2] >> (even ? 4 : 0)) & 0x0f;
          }
  
          case 8:
              return row[i];
  
          default:
              UNREACHABLE();
              return 0;
      }
  }
  
  R8G8B8A8 DecodeColor(const uint8_t *src,
                       uint32_t redBlueBits,
                       uint32_t greenBits,
                       uint32_t alphaBits)
  {
      switch (redBlueBits)
      {
          case 8:
              ASSERT(greenBits == 8);
              switch (alphaBits)
              {
                  case 0:
                      return ReadColor<>(reinterpret_cast<const R8G8B8 *>(src));
                  case 8:
                      return ReadColor<>(reinterpret_cast<const R8G8B8A8 *>(src));
                  default:
                      UNREACHABLE();
                      break;
              }
              break;
  
          case 5:
              switch (greenBits)
              {
                  case 6:
                      ASSERT(alphaBits == 0);
                      return ReadColor<>(reinterpret_cast<const R5G6B5 *>(src));
                  case 5:
                      ASSERT(alphaBits == 1);
                      return ReadColor<>(reinterpret_cast<const R5G5B5A1 *>(src));
                  default:
                      UNREACHABLE();
                      break;
              }
              break;
  
          case 4:
              ASSERT(greenBits == 4 && alphaBits == 4);
              return ReadColor<>(reinterpret_cast<const R4G4B4A4 *>(src));
  
          default:
              UNREACHABLE();
              break;
      }
  
      UNREACHABLE();
      return R8G8B8A8{0, 0, 0, 255};
  }
  
  }  // namespace
  
  // See LoadPalettedToRGBA8.
  void LoadPalettedToRGBA8Impl(size_t width,
                               size_t height,
                               size_t depth,
                               uint32_t indexBits,
                               uint32_t redBlueBits,
                               uint32_t greenBits,
                               uint32_t alphaBits,
                               const uint8_t *input,
                               size_t inputRowPitch,
                               size_t inputDepthPitch,
                               uint8_t *output,
                               size_t outputRowPitch,
                               size_t outputDepthPitch)
  {
      size_t colorBytes   = (redBlueBits + greenBits + redBlueBits + alphaBits) / 8;
      size_t paletteSize  = 1 << indexBits;
      size_t paletteBytes = paletteSize * colorBytes;
  
      const uint8_t *palette = input;
  
      const uint8_t *texels = input + paletteBytes;  // + TODO(http://anglebug.com/7688): mip levels
  
      for (size_t z = 0; z < depth; z++)
      {
          for (size_t y = 0; y < height; y++)
          {
              const uint8_t *srcRow =
                  priv::OffsetDataPointer<uint8_t>(texels, y, z, inputRowPitch, inputDepthPitch);
              R8G8B8A8 *dstRow =
                  priv::OffsetDataPointer<R8G8B8A8>(output, y, z, outputRowPitch, outputDepthPitch);
  
              for (size_t x = 0; x < width; x++)
              {
                  size_t indexIntoPalette = DecodeIndexIntoPalette(srcRow, x, indexBits);
  
                  dstRow[x] = DecodeColor(palette + indexIntoPalette * colorBytes, redBlueBits,
                                          greenBits, alphaBits);
              }
          }
      }
  }
  
  }  // namespace angle
  

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