| /* |
| * Copyright 2017 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "gm/gm.h" |
| #include "include/core/SkBlendMode.h" |
| #include "include/core/SkCanvas.h" |
| #include "include/core/SkColor.h" |
| #include "include/core/SkFont.h" |
| #include "include/core/SkPaint.h" |
| #include "include/core/SkTypeface.h" |
| #include "include/core/SkTypes.h" |
| #include "tools/Resources.h" |
| #include "tools/ToolUtils.h" |
| |
| // Hue, Saturation, Color, and Luminosity blend modes are oddballs. |
| // They nominally convert their inputs to unpremul, then to HSL, then |
| // mix-and-match H,S,and L from Src and Dst, then convert back, then premul. |
| // |
| // In practice that's slow, so instead we pick the color with the correct |
| // Hue, and then (approximately) apply the other's Saturation and/or Luminosity. |
| // This isn't just an optimization... it's how the modes are specified. |
| // |
| // Each mode's name describes the Src H,S,L components to keep, taking the |
| // others from Dst, where Color == Hue + Saturation. Color and Luminosity |
| // are each other's complements; Hue and Saturation have no complement. |
| // |
| // All these modes were originally designed to operate on gamma-encoded values, |
| // and that's what everyone's used to seeing. It's unclear wehther they make |
| // any sense in a gamma-correct world. They certainly won't look at all similar. |
| // |
| // We have had many inconsistent implementations of these modes. |
| // This GM tries to demonstrate unambigously how they should work. |
| // |
| // To go along with our inconsistent implementations, there are two slightly |
| // inconsistent specifications of how to perform these blends, |
| // web: https://www.w3.org/TR/compositing-1/#blendingnonseparable |
| // KHR: https://www.khronos.org/registry/OpenGL/extensions/KHR/KHR_blend_equation_advanced.txt |
| // It looks like these are meant to be identical, but they disagree on at least ClipColor(). |
| // |
| // I think the KHR version is just wrong... it produces values >1. So we use the web version. |
| |
| static float min(float r, float g, float b) { return std::min(r, std::min(g, b)); } |
| static float max(float r, float g, float b) { return std::max(r, std::max(g, b)); } |
| |
| static float sat(float r, float g, float b) { return max(r,g,b) - min(r,g,b); } |
| static float lum(float r, float g, float b) { return r*0.30f + g*0.59f + b*0.11f; } |
| |
| // The two SetSat() routines in the specs look different, but they're logically equivalent. |
| // Both map the minimum channel to 0, maximum to s, and scale the middle proportionately. |
| // The KHR version has done a better job at simplifying its math, so we use it here. |
| static void set_sat(float* r, float* g, float* b, float s) { |
| float mn = min(*r,*g,*b), |
| mx = max(*r,*g,*b); |
| auto channel = [=](float c) { |
| return mx == mn ? 0 |
| : (c - mn) * s / (mx - mn); |
| }; |
| *r = channel(*r); |
| *g = channel(*g); |
| *b = channel(*b); |
| } |
| static void clip_color(float* r, float* g, float* b) { |
| float l = lum(*r,*g,*b), |
| mn = min(*r,*g,*b), |
| mx = max(*r,*g,*b); |
| auto clip = [=](float c) { |
| if (mn < 0) { c = l + (c - l) * ( l) / (l - mn); } |
| if (mx > 1) { c = l + (c - l) * (1 - l) / (mx - l); } |
| SkASSERT(-0.0001f < c); // This may end up very slightly negative... |
| SkASSERT( c <= 1); |
| return c; |
| }; |
| *r = clip(*r); |
| *g = clip(*g); |
| *b = clip(*b); |
| } |
| static void set_lum(float* r, float* g, float* b, float l) { |
| float diff = l - lum(*r,*g,*b); |
| *r += diff; |
| *g += diff; |
| *b += diff; |
| clip_color(r,g,b); |
| } |
| |
| |
| static void hue(float dr, float dg, float db, |
| float* sr, float* sg, float* sb) { |
| // Hue of Src, Saturation and Luminosity of Dst. |
| float R = *sr, |
| G = *sg, |
| B = *sb; |
| set_sat(&R,&G,&B, sat(dr,dg,db)); |
| set_lum(&R,&G,&B, lum(dr,dg,db)); |
| *sr = R; |
| *sg = G; |
| *sb = B; |
| } |
| |
| static void saturation(float dr, float dg, float db, |
| float* sr, float* sg, float* sb) { |
| // Saturation of Src, Hue and Luminosity of Dst |
| float R = dr, |
| G = dg, |
| B = db; |
| set_sat(&R,&G,&B, sat(*sr,*sg,*sb)); |
| set_lum(&R,&G,&B, lum( dr, dg, db)); // This may seem redundant, but it is not. |
| *sr = R; |
| *sg = G; |
| *sb = B; |
| } |
| |
| static void color(float dr, float dg, float db, |
| float* sr, float* sg, float* sb) { |
| // Hue and Saturation of Src, Luminosity of Dst. |
| float R = *sr, |
| G = *sg, |
| B = *sb; |
| set_lum(&R,&G,&B, lum(dr,dg,db)); |
| *sr = R; |
| *sg = G; |
| *sb = B; |
| } |
| |
| static void luminosity(float dr, float dg, float db, |
| float* sr, float* sg, float* sb) { |
| // Luminosity of Src, Hue and Saturation of Dst. |
| float R = dr, |
| G = dg, |
| B = db; |
| set_lum(&R,&G,&B, lum(*sr,*sg,*sb)); |
| *sr = R; |
| *sg = G; |
| *sb = B; |
| } |
| |
| static SkColor blend(SkColor dst, SkColor src, |
| void (*mode)(float,float,float, float*,float*,float*)) { |
| |
| SkASSERT(SkColorGetA(dst) == 0xff |
| && SkColorGetA(src) == 0xff); // Not fundamental, just simplifying for this GM. |
| |
| SkColor4f d = SkColor4f::FromColor(dst), |
| s = SkColor4f::FromColor(src); |
| |
| mode( d.fR, d.fG, d.fB, |
| &s.fR, &s.fG, &s.fB); |
| |
| return s.toSkColor(); |
| } |
| |
| DEF_SIMPLE_GM(hsl, canvas, 600, 100) { |
| SkPaint paint; |
| SkFont font(ToolUtils::create_portable_typeface()); |
| |
| const char* comment = "HSL blend modes are correct when you see no circles in the squares."; |
| canvas->drawString(comment, 10,10, font, paint); |
| |
| // Just to keep things reaaaal simple, we'll only use opaque colors. |
| SkPaint bg, fg; |
| bg.setColor(0xff00ff00); // Fully-saturated bright green, H = 120°, S = 100%, L = 50%. |
| fg.setColor(0xff7f3f7f); // Partly-saturated dim magenta, H = 300°, S = ~33%, L = ~37%. |
| |
| struct { |
| SkBlendMode mode; |
| void (*reference)(float,float,float, float*,float*,float*); |
| } tests[] = { |
| { SkBlendMode::kSrc, nullptr }, |
| { SkBlendMode::kDst, nullptr }, |
| { SkBlendMode::kHue, hue }, |
| { SkBlendMode::kSaturation, saturation }, |
| { SkBlendMode::kColor, color }, |
| { SkBlendMode::kLuminosity, luminosity }, |
| }; |
| for (auto test : tests) { |
| canvas->drawRect({20,20,80,80}, bg); |
| |
| fg.setBlendMode(test.mode); |
| canvas->drawRect({20,20,80,80}, fg); |
| |
| if (test.reference) { |
| SkPaint ref; |
| ref.setColor(blend(bg.getColor(), fg.getColor(), test.reference)); |
| canvas->drawCircle(50,50, 20, ref); |
| } |
| |
| canvas->drawString(SkBlendMode_Name(test.mode), 20, 90, font, paint); |
| |
| canvas->translate(100,0); |
| } |
| } |
| |
| #include "include/effects/SkGradientShader.h" |
| |
| // Trying to match sample images on https://www.w3.org/TR/compositing-1/#blendingnonseparable |
| // |
| static sk_sp<SkShader> make_grad(SkScalar width) { |
| SkColor colors[] = { |
| 0xFF00CCCC, 0xFF0000CC, 0xFFCC00CC, 0xFFCC0000, 0xFFCCCC00, 0xFF00CC00, |
| }; |
| SkPoint pts[] = {{0, 0}, {width, 0}}; |
| |
| return SkGradientShader::MakeLinear(pts, colors, nullptr, std::size(colors), |
| SkTileMode::kClamp); |
| } |
| |
| DEF_SIMPLE_GM(HSL_duck, canvas, 1110, 620) { |
| auto src = GetResourceAsImage("images/ducky.png"); |
| auto dst = make_grad(src->width()); |
| SkRect r = SkRect::MakeIWH(src->width(), src->height()); |
| |
| canvas->translate(10, 50); |
| canvas->scale(0.5f, 0.5f); |
| |
| const struct { |
| SkBlendMode fMode; |
| const char* fName; |
| } recs[] = { |
| { SkBlendMode::kHue, "Hue" }, |
| { SkBlendMode::kSaturation, "Saturation" }, |
| { SkBlendMode::kColor, "Color" }, |
| { SkBlendMode::kLuminosity, "Luminosity" }, |
| }; |
| |
| SkFont font; |
| font.setSize(40); |
| font.setEdging(SkFont::Edging::kAntiAlias); |
| |
| canvas->save(); |
| for (auto [_, name] : recs) { |
| canvas->drawSimpleText(name, strlen(name), SkTextEncoding::kUTF8, 150, -20, |
| font, SkPaint()); |
| canvas->translate(r.width() + 10, 0); |
| } |
| canvas->restore(); |
| |
| for (SkScalar src_a : {1.0f, 0.5f}) { |
| canvas->save(); |
| for (auto [mode, _] : recs) { |
| SkPaint p; |
| p.setShader(dst); |
| canvas->drawRect(r, p); // bg |
| |
| p.setShader(nullptr); |
| p.setBlendMode(mode); |
| p.setAlphaf(src_a); |
| canvas->drawImageRect(src, r, SkSamplingOptions(), &p); |
| |
| canvas->translate(r.width() + 10, 0); |
| } |
| SkString str; |
| str.printf("alpha %g", src_a); |
| canvas->drawSimpleText(str.c_str(), str.size(), SkTextEncoding::kUTF8, 10, r.height()/2, |
| font, SkPaint()); |
| |
| canvas->restore(); |
| canvas->translate(0, r.height() + 10); |
| } |
| } |