static inline void test_fast_interp(skiatest::Reporter* reporter) {
SkRandom r;
U8CPU a0 = 0;
U8CPU a255 = 255;
for (int i = 0; i < 200; i++) {
SkColor colorSrc = r.nextU();
SkColor colorDst = r.nextU();
SkPMColor src = SkPreMultiplyColor(colorSrc);
SkPMColor dst = SkPreMultiplyColor(colorDst);
REPORTER_ASSERT(reporter, SkFastFourByteInterp(src, dst, a0) == dst);
REPORTER_ASSERT(reporter, SkFastFourByteInterp(src, dst, a255) == src);
}
}
// Linear interpolation (lerp) is unnecessary if there are no sharp
// discontinuities in the gradient - which must be true if there are
// only 2 colors - but it's cheap.
void shadeSpan_linear_vertical_lerp(TileProc proc, SkFixed dx, SkFixed fx,
SkPMColor* SK_RESTRICT dstC,
const SkPMColor* SK_RESTRICT cache,
int toggle, int count) {
// We're a vertical gradient, so no change in a span.
// If colors change sharply across the gradient, dithering is
// insufficient (it subsamples the color space) and we need to lerp.
unsigned fullIndex = proc(fx);
unsigned fi = fullIndex >> (16 - SkGradientShaderBase::kCache32Bits);
unsigned remainder = fullIndex & SkGradientShaderBase::kLerpRemainderMask32;
SkPMColor lerp =
SkFastFourByteInterp(
cache[toggle + fi + 1],
cache[toggle + fi], remainder);
SkPMColor dlerp =
SkFastFourByteInterp(
cache[(toggle ^ SkGradientShaderBase::kDitherStride32) + fi + 1],
cache[(toggle ^ SkGradientShaderBase::kDitherStride32) + fi], remainder);
sk_memset32_dither(dstC, lerp, dlerp, count);
}
void shadeSpan_linear_clamp(TileProc proc, SkFixed dx, SkFixed fx,
SkPMColor* SK_RESTRICT dstC,
const SkPMColor* SK_RESTRICT cache,
int toggle, int count) {
SkClampRange range;
range.init(fx, dx, count, 0, SkGradientShaderBase::kGradient32Length);
