void draw(SkCanvas* canvas) {
SkBitmap bitmap;
bitmap.setInfo(SkImageInfo::MakeN32(16, 32, kPremul_SkAlphaType,
SkColorSpace::MakeSRGBLinear()));
SkColorSpace* colorSpace = bitmap.colorSpace();
SkDebugf("gammaCloseToSRGB: %s gammaIsLinear: %s isSRGB: %s\n",
colorSpace->gammaCloseToSRGB() ? "true" : "false",
colorSpace->gammaIsLinear() ? "true" : "false",
colorSpace->isSRGB() ? "true" : "false");
}
sk_sp<SkData> encode_bitmap_for_png(SkBitmap bitmap) {
const int w = bitmap.width(),
h = bitmap.height();
// PNG wants unpremultiplied 8-bit RGBA pixels (16-bit could work fine too).
// We leave the gamma of these bytes unspecified, to continue the status quo,
// which we think generally is to interpret them as sRGB.
SkAutoTMalloc<uint32_t> rgba(w*h);
auto srgbColorSpace = SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named);
if (bitmap. colorType() == kN32_SkColorType &&
bitmap.colorSpace() == srgbColorSpace.get()) {
// These are premul sRGB 8-bit pixels in SkPMColor order.
// We want unpremul sRGB 8-bit pixels in RGBA order. We'll get there via floats.
bitmap.lockPixels();
auto px = (const uint32_t*)bitmap.getPixels();
if (!px) {
return nullptr;
}
for (int i = 0; i < w*h; i++) {
Sk4f fs = Sk4f_fromS32(px[i]); // Convert up to linear floats.
#if defined(SK_PMCOLOR_IS_BGRA)
fs = SkNx_shuffle<2,1,0,3>(fs); // Shuffle to RGBA, if not there already.
#endif
float invA = 1.0f / fs[3];
fs = fs * Sk4f(invA, invA, invA, 1); // Unpremultiply.
rgba[i] = Sk4f_toS32(fs); // Pack down to sRGB bytes.
}
} else if (bitmap.colorType() == kRGBA_F16_SkColorType) {
// These are premul linear half-float pixels in RGBA order.
// We want unpremul sRGB 8-bit pixels in RGBA order. We'll get there via floats.
bitmap.lockPixels();
auto px = (const uint64_t*)bitmap.getPixels();
if (!px) {
return nullptr;
}
for (int i = 0; i < w*h; i++) {
// Convert up to linear floats.
Sk4f fs(SkHalfToFloat(static_cast<SkHalf>(px[i] >> (0 * 16))),
SkHalfToFloat(static_cast<SkHalf>(px[i] >> (1 * 16))),
SkHalfToFloat(static_cast<SkHalf>(px[i] >> (2 * 16))),
SkHalfToFloat(static_cast<SkHalf>(px[i] >> (3 * 16))));
fs = Sk4f::Max(0.0f, Sk4f::Min(fs, 1.0f)); // Clamp
float invA = 1.0f / fs[3];
fs = fs * Sk4f(invA, invA, invA, 1); // Unpremultiply.
rgba[i] = Sk4f_toS32(fs); // Pack down to sRGB bytes.
}
} else {
