// Note: SkColorTable claims to store SkPMColors, which is not necessarily
// the case here.
bool SkPngCodec::createColorTable(SkColorType dstColorType, bool premultiply, int* ctableCount) {
int numColors;
png_color* palette;
if (!png_get_PLTE(fPng_ptr, fInfo_ptr, &palette, &numColors)) {
return false;
}
// Note: These are not necessarily SkPMColors.
SkPMColor colorPtr[256];
png_bytep alphas;
int numColorsWithAlpha = 0;
if (png_get_tRNS(fPng_ptr, fInfo_ptr, &alphas, &numColorsWithAlpha, nullptr)) {
// Choose which function to use to create the color table. If the final destination's
// colortype is unpremultiplied, the color table will store unpremultiplied colors.
PackColorProc proc = choose_pack_color_proc(premultiply, dstColorType);
for (int i = 0; i < numColorsWithAlpha; i++) {
// We don't have a function in SkOpts that combines a set of alphas with a set
// of RGBs. We could write one, but it's hardly worth it, given that this
// is such a small fraction of the total decode time.
colorPtr[i] = proc(alphas[i], palette->red, palette->green, palette->blue);
palette++;
}
}
if (numColorsWithAlpha < numColors) {
// The optimized code depends on a 3-byte png_color struct with the colors
// in RGB order. These checks make sure it is safe to use.
static_assert(3 == sizeof(png_color), "png_color struct has changed. Opts are broken.");
#ifdef SK_DEBUG
SkASSERT(&palette->red < &palette->green);
SkASSERT(&palette->green < &palette->blue);
#endif
if (is_rgba(dstColorType)) {
SkOpts::RGB_to_RGB1(colorPtr + numColorsWithAlpha, palette,
numColors - numColorsWithAlpha);
} else {
SkOpts::RGB_to_BGR1(colorPtr + numColorsWithAlpha, palette,
numColors - numColorsWithAlpha);
}
}
// Pad the color table with the last color in the table (or black) in the case that
// invalid pixel indices exceed the number of colors in the table.
const int maxColors = 1 << fBitDepth;
if (numColors < maxColors) {
SkPMColor lastColor = numColors > 0 ? colorPtr[numColors - 1] : SK_ColorBLACK;
sk_memset32(colorPtr + numColors, lastColor, maxColors - numColors);
}
// Set the new color count.
if (ctableCount != nullptr) {
*ctableCount = maxColors;
}
fColorTable.reset(new SkColorTable(colorPtr, maxColors));
return true;
}
// Note: SkColorTable claims to store SkPMColors, which is not necessarily the case here.
bool SkPngCodec::createColorTable(const SkImageInfo& dstInfo, int* ctableCount) {
int numColors;
png_color* palette;
if (!png_get_PLTE(fPng_ptr, fInfo_ptr, &palette, &numColors)) {
return false;
}
// Contents depend on tableColorType and our choice of if/when to premultiply:
// { kPremul, kUnpremul, kOpaque } x { RGBA, BGRA }
SkPMColor colorTable[256];
SkColorType tableColorType = fColorXform ? kRGBA_8888_SkColorType : dstInfo.colorType();
png_bytep alphas;
int numColorsWithAlpha = 0;
if (png_get_tRNS(fPng_ptr, fInfo_ptr, &alphas, &numColorsWithAlpha, nullptr)) {
// If we are performing a color xform, it will handle the premultiply. Otherwise,
// we'll do it here.
bool premultiply = !fColorXform && needs_premul(dstInfo, this->getInfo());
// Choose which function to use to create the color table. If the final destination's
// colortype is unpremultiplied, the color table will store unpremultiplied colors.
PackColorProc proc = choose_pack_color_proc(premultiply, tableColorType);
for (int i = 0; i < numColorsWithAlpha; i++) {
// We don't have a function in SkOpts that combines a set of alphas with a set
// of RGBs. We could write one, but it's hardly worth it, given that this
// is such a small fraction of the total decode time.
colorTable[i] = proc(alphas[i], palette->red, palette->green, palette->blue);
palette++;
}
}
if (numColorsWithAlpha < numColors) {
// The optimized code depends on a 3-byte png_color struct with the colors
// in RGB order. These checks make sure it is safe to use.
static_assert(3 == sizeof(png_color), "png_color struct has changed. Opts are broken.");
#ifdef SK_DEBUG
SkASSERT(&palette->red < &palette->green);
SkASSERT(&palette->green < &palette->blue);
#endif
if (is_rgba(tableColorType)) {
SkOpts::RGB_to_RGB1(colorTable + numColorsWithAlpha, palette,
numColors - numColorsWithAlpha);
} else {
SkOpts::RGB_to_BGR1(colorTable + numColorsWithAlpha, palette,
numColors - numColorsWithAlpha);
}
}
// If we are not decoding to F16, we can color xform now and store the results
// in the color table.
if (fColorXform && kRGBA_F16_SkColorType != dstInfo.colorType()) {
SkColorType xformColorType = is_rgba(dstInfo.colorType()) ?
kRGBA_8888_SkColorType : kBGRA_8888_SkColorType;
SkAlphaType xformAlphaType = xform_alpha_type(dstInfo.alphaType(),
this->getInfo().alphaType());
fColorXform->apply(colorTable, colorTable, numColors, xformColorType, xformAlphaType);
}
// Pad the color table with the last color in the table (or black) in the case that
// invalid pixel indices exceed the number of colors in the table.
const int maxColors = 1 << fBitDepth;
if (numColors < maxColors) {
SkPMColor lastColor = numColors > 0 ? colorTable[numColors - 1] : SK_ColorBLACK;
sk_memset32(colorTable + numColors, lastColor, maxColors - numColors);
}
// Set the new color count.
if (ctableCount != nullptr) {
*ctableCount = maxColors;
}
fColorTable.reset(new SkColorTable(colorTable, maxColors));
return true;
}