text: /*
   * Copyright 2014 Google Inc.
   *
   * Use of this source code is governed by a BSD-style license that can be
   * found in the LICENSE file.
   */
  
  #include "SkBitmap.h"
  #include "SkCanvas.h"
  #include "SkConfig8888.h"
  #include "SkColorPriv.h"
  #include "SkDither.h"
  #include "SkMathPriv.h"
  #include "SkUnPreMultiply.h"
  
  enum AlphaVerb {
      kNothing_AlphaVerb,
      kPremul_AlphaVerb,
      kUnpremul_AlphaVerb,
  };
  
  template <bool doSwapRB, AlphaVerb doAlpha> uint32_t convert32(uint32_t c) {
      if (doSwapRB) {
          c = SkSwizzle_RB(c);
      }
  
      // Lucky for us, in both RGBA and BGRA, the alpha component is always in the same place, so
      // we can perform premul or unpremul the same way without knowing the swizzles for RGB.
      switch (doAlpha) {
          case kNothing_AlphaVerb:
              // no change
              break;
          case kPremul_AlphaVerb:
              c = SkPreMultiplyARGB(SkGetPackedA32(c), SkGetPackedR32(c),
                                    SkGetPackedG32(c), SkGetPackedB32(c));
              break;
          case kUnpremul_AlphaVerb:
              c = SkUnPreMultiply::UnPreMultiplyPreservingByteOrder(c);
              break;
      }
      return c;
  }
  
  template <bool doSwapRB, AlphaVerb doAlpha>
  void convert32_row(uint32_t* dst, const uint32_t* src, int count) {
      // This has to be correct if src == dst (but not partial overlap)
      for (int i = 0; i < count; ++i) {
          dst[i] = convert32<doSwapRB, doAlpha>(src[i]);
      }
  }
  
  static bool is_32bit_colortype(SkColorType ct) {
      return kRGBA_8888_SkColorType == ct || kBGRA_8888_SkColorType == ct;
  }
  
  static AlphaVerb compute_AlphaVerb(SkAlphaType src, SkAlphaType dst) {
      SkASSERT(kUnknown_SkAlphaType != src);
      SkASSERT(kUnknown_SkAlphaType != dst);
  
      if (kOpaque_SkAlphaType == src || kOpaque_SkAlphaType == dst || src == dst) {
          return kNothing_AlphaVerb;
      }
      if (kPremul_SkAlphaType == dst) {
          SkASSERT(kUnpremul_SkAlphaType == src);
          return kPremul_AlphaVerb;
      } else {
          SkASSERT(kPremul_SkAlphaType == src);
          SkASSERT(kUnpremul_SkAlphaType == dst);
          return kUnpremul_AlphaVerb;
      }
  }
  
  static void memcpy32_row(uint32_t* dst, const uint32_t* src, int count) {
      memcpy(dst, src, count * 4);
  }
  
  bool SkSrcPixelInfo::convertPixelsTo(SkDstPixelInfo* dst, int width, int height) const {
      if (width <= 0 || height <= 0) {
          return false;
      }
  
      if (!is_32bit_colortype(fColorType) || !is_32bit_colortype(dst->fColorType)) {
          return false;
      }
  
      void (*proc)(uint32_t* dst, const uint32_t* src, int count);
      AlphaVerb doAlpha = compute_AlphaVerb(fAlphaType, dst->fAlphaType);
      bool doSwapRB = fColorType != dst->fColorType;
  
      switch (doAlpha) {
          case kNothing_AlphaVerb:
              if (doSwapRB) {
                  proc = convert32_row<true, kNothing_AlphaVerb>;
              } else {
                  if (fPixels == dst->fPixels) {
                      return true;
                  }
                  proc = memcpy32_row;
              }
              break;
          case kPremul_AlphaVerb:
              if (doSwapRB) {
                  proc = convert32_row<true, kPremul_AlphaVerb>;
              } else {
                  proc = convert32_row<false, kPremul_AlphaVerb>;
              }
              break;
          case kUnpremul_AlphaVerb:
              if (doSwapRB) {
                  proc = convert32_row<true, kUnpremul_AlphaVerb>;
              } else {
                  proc = convert32_row<false, kUnpremul_AlphaVerb>;
              }
              break;
      }
  
      uint32_t* dstP = static_cast<uint32_t*>(dst->fPixels);
      const uint32_t* srcP = static_cast<const uint32_t*>(fPixels);
      size_t srcInc = fRowBytes >> 2;
      size_t dstInc = dst->fRowBytes >> 2;
      for (int y = 0; y < height; ++y) {
          proc(dstP, srcP, width);
          dstP += dstInc;
          srcP += srcInc;
      }
      return true;
  }
  
  static void rect_memcpy(void* dst, size_t dstRB, const void* src, size_t srcRB, size_t bytesPerRow,
                          int rowCount) {
      SkASSERT(bytesPerRow <= srcRB);
      SkASSERT(bytesPerRow <= dstRB);
      for (int i = 0; i < rowCount; ++i) {
          memcpy(dst, src, bytesPerRow);
          dst = (char*)dst + dstRB;
          src = (const char*)src + srcRB;
      }
  }
  
  static void copy_g8_to_32(void* dst, size_t dstRB, const void* src, size_t srcRB, int w, int h) {
      uint32_t* dst32 = (uint32_t*)dst;
      const uint8_t* src8 = (const uint8_t*)src;
      
      for (int y = 0; y < h; ++y) {
          for (int x = 0; x < w; ++x) {
              dst32[x] = SkPackARGB32(0xFF, src8[x], src8[x], src8[x]);
          }
          dst32 = (uint32_t*)((char*)dst32 + dstRB);
          src8 += srcRB;
      }
  }
  
  static void copy_32_to_g8(void* dst, size_t dstRB, const void* src, size_t srcRB,
                            const SkImageInfo& srcInfo) {
      uint8_t* dst8 = (uint8_t*)dst;
      const uint32_t* src32 = (const uint32_t*)src;
  
      const int w = srcInfo.width();
      const int h = srcInfo.height();
      const bool isBGRA = (kBGRA_8888_SkColorType == srcInfo.colorType());
  
      for (int y = 0; y < h; ++y) {
          if (isBGRA) {
              // BGRA
              for (int x = 0; x < w; ++x) {
                  uint32_t s = src32[x];
                  dst8[x] = SkComputeLuminance((s >> 16) & 0xFF, (s >> 8) & 0xFF, s & 0xFF);
              }
          } else {
              // RGBA
              for (int x = 0; x < w; ++x) {
                  uint32_t s = src32[x];
                  dst8[x] = SkComputeLuminance(s & 0xFF, (s >> 8) & 0xFF, (s >> 16) & 0xFF);
              }
          }
          src32 = (const uint32_t*)((const char*)src32 + srcRB);
          dst8 += dstRB;
      }
  }
  
  bool SkPixelInfo::CopyPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRB,
                               const SkImageInfo& srcInfo, const void* srcPixels, size_t srcRB,
                               SkColorTable* ctable) {
      if (srcInfo.dimensions() != dstInfo.dimensions()) {
          return false;
      }
  
      const int width = srcInfo.width();
      const int height = srcInfo.height();
  
      // Handle fancy alpha swizzling if both are ARGB32
      if (4 == srcInfo.bytesPerPixel() && 4 == dstInfo.bytesPerPixel()) {
          SkDstPixelInfo dstPI;
          dstPI.fColorType = dstInfo.colorType();
          dstPI.fAlphaType = dstInfo.alphaType();
          dstPI.fPixels = dstPixels;
          dstPI.fRowBytes = dstRB;
  
          SkSrcPixelInfo srcPI;
          srcPI.fColorType = srcInfo.colorType();
          srcPI.fAlphaType = srcInfo.alphaType();
          srcPI.fPixels = srcPixels;
          srcPI.fRowBytes = srcRB;
  
          return srcPI.convertPixelsTo(&dstPI, width, height);
      }
  
      // If they agree on colorType and the alphaTypes are compatible, then we just memcpy.
      // Note: we've already taken care of 32bit colortypes above.
      if (srcInfo.colorType() == dstInfo.colorType()) {
          switch (srcInfo.colorType()) {
              case kRGB_565_SkColorType:
              case kAlpha_8_SkColorType:
              case kGray_8_SkColorType:
                  break;
              case kIndex_8_SkColorType:
              case kARGB_4444_SkColorType:
                  if (srcInfo.alphaType() != dstInfo.alphaType()) {
                      return false;
                  }
                  break;
              default:
                  return false;
          }
          rect_memcpy(dstPixels, dstRB, srcPixels, srcRB, width * srcInfo.bytesPerPixel(), height);
          return true;
      }
  
      /*
       *  Begin section where we try to change colorTypes along the way. Not all combinations
       *  are supported.
       */
  
      if (kGray_8_SkColorType == srcInfo.colorType() && 4 == dstInfo.bytesPerPixel()) {
          copy_g8_to_32(dstPixels, dstRB, srcPixels, srcRB, width, height);
          return true;
      }
      if (kGray_8_SkColorType == dstInfo.colorType() && 4 == srcInfo.bytesPerPixel()) {
          copy_32_to_g8(dstPixels, dstRB, srcPixels, srcRB, srcInfo);
          return true;
      }
  
      // Can no longer draw directly into 4444, but we can manually whack it for a few combinations
      if (kARGB_4444_SkColorType == dstInfo.colorType() &&
          (kN32_SkColorType == srcInfo.colorType() || kIndex_8_SkColorType == srcInfo.colorType())) {
          if (srcInfo.alphaType() == kUnpremul_SkAlphaType) {
              // Our method for converting to 4444 assumes premultiplied.
              return false;
          }
  
          const SkPMColor* table = NULL;
          if (kIndex_8_SkColorType == srcInfo.colorType()) {
              if (NULL == ctable) {
                  return false;
              }
              table = ctable->readColors();
          }
  
          for (int y = 0; y < height; ++y) {
              DITHER_4444_SCAN(y);
              SkPMColor16* SK_RESTRICT dstRow = (SkPMColor16*)dstPixels;
              if (table) {
                  const uint8_t* SK_RESTRICT srcRow = (const uint8_t*)srcPixels;
                  for (int x = 0; x < width; ++x) {
                      dstRow[x] = SkDitherARGB32To4444(table[srcRow[x]], DITHER_VALUE(x));
                  }
              } else {
                  const SkPMColor* SK_RESTRICT srcRow = (const SkPMColor*)srcPixels;
                  for (int x = 0; x < width; ++x) {
                      dstRow[x] = SkDitherARGB32To4444(srcRow[x], DITHER_VALUE(x));
                  }
              }
              dstPixels = (char*)dstPixels + dstRB;
              srcPixels = (const char*)srcPixels + srcRB;
          }
          return true;
      }
  
      if (dstInfo.alphaType() == kUnpremul_SkAlphaType) {
          // We do not support drawing to unpremultiplied bitmaps.
          return false;
      }
  
      // Final fall-back, draw with a canvas
      //
      // Always clear the dest in case one of the blitters accesses it
      // TODO: switch the allocation of tmpDst to call sk_calloc_throw
      {
          SkBitmap bm;
          if (!bm.installPixels(srcInfo, const_cast<void*>(srcPixels), srcRB, ctable, NULL, NULL)) {
              return false;
          }
          SkAutoTUnref<SkCanvas> canvas(SkCanvas::NewRasterDirect(dstInfo, dstPixels, dstRB));
          if (NULL == canvas.get()) {
              return false;
          }
  
          SkPaint  paint;
          paint.setDither(true);
  
          canvas->clear(0);
          canvas->drawBitmap(bm, 0, 0, &paint);
          return true;
      }
  }
  
  