| /* |
| * Copyright 2018 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| // This controls the range of values added to color channels |
| layout(key) in int rangeType; |
| |
| @make { |
| static std::unique_ptr<GrFragmentProcessor> Make(GrPixelConfig dstConfig) { |
| int rangeType; |
| switch (dstConfig) { |
| case kGray_8_GrPixelConfig: |
| case kGray_8_as_Lum_GrPixelConfig: |
| case kGray_8_as_Red_GrPixelConfig: |
| case kRGBA_8888_GrPixelConfig: |
| case kBGRA_8888_GrPixelConfig: |
| case kSRGBA_8888_GrPixelConfig: |
| case kSBGRA_8888_GrPixelConfig: |
| rangeType = 0; |
| break; |
| case kRGB_565_GrPixelConfig: |
| rangeType = 1; |
| break; |
| case kRGBA_4444_GrPixelConfig: |
| rangeType = 2; |
| break; |
| case kUnknown_GrPixelConfig: |
| case kRGBA_1010102_GrPixelConfig: |
| case kAlpha_half_GrPixelConfig: |
| case kAlpha_half_as_Red_GrPixelConfig: |
| case kRGBA_float_GrPixelConfig: |
| case kRG_float_GrPixelConfig: |
| case kRGBA_half_GrPixelConfig: |
| case kAlpha_8_GrPixelConfig: |
| case kAlpha_8_as_Alpha_GrPixelConfig: |
| case kAlpha_8_as_Red_GrPixelConfig: |
| return nullptr; |
| } |
| return std::unique_ptr<GrFragmentProcessor>(new GrDitherEffect(rangeType)); |
| } |
| } |
| |
| void main() { |
| half value; |
| half range; |
| @switch (rangeType) { |
| case 0: |
| range = 1.0 / 255.0; |
| break; |
| case 1: |
| range = 1.0 / 63.0; |
| break; |
| default: |
| // Experimentally this looks better than the expected value of 1/15. |
| range = 1.0 / 15.0; |
| break; |
| } |
| @if (sk_Caps.integerSupport) { |
| // This ordered-dither code is lifted from the cpu backend. |
| uint x = uint(sk_FragCoord.x); |
| uint y = uint(sk_FragCoord.y); |
| uint m = (y & 1) << 5 | (x & 1) << 4 | |
| (y & 2) << 2 | (x & 2) << 1 | |
| (y & 4) >> 1 | (x & 4) >> 2; |
| value = half(m) * 1.0 / 64.0 - 63.0 / 128.0; |
| } else { |
| // Simulate the integer effect used above using step/mod. For speed, simulates a 4x4 |
| // dither pattern rather than an 8x8 one. |
| half4 modValues = mod(sk_FragCoord.xyxy, half4(2.0, 2.0, 4.0, 4.0)); |
| half4 stepValues = step(modValues, half4(1.0, 1.0, 2.0, 2.0)); |
| value = dot(stepValues, half4(8.0 / 16.0, 4.0 / 16.0, 2.0 / 16.0, 1.0 / 16.0)) - 15.0 / 32.0; |
| } |
| // For each color channel, add the random offset to the channel value and then clamp |
| // between 0 and alpha to keep the color premultiplied. |
| sk_OutColor = half4(clamp(sk_InColor.rgb + value * range, 0, sk_InColor.a), sk_InColor.a); |
| } |
| |
| @test(testData) { |
| float range = testData->fRandom->nextRangeF(0.001f, 0.05f); |
| return std::unique_ptr<GrFragmentProcessor>(new GrDitherEffect(range)); |
| } |