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/*
* 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.h"
#include "sk_tool_utils.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.
//
// 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.
//
// We have had many inconsistent implementations of these modes.
// This GM tries to demonstrate unambigously how they should work.
//
// TODO: double- and triple-check expected colors
// TODO: how does gamma-correction factor into this?
DEF_SIMPLE_GM(hsl, canvas, 600, 100) {
SkPaint label;
sk_tool_utils::set_portable_typeface(&label);
label.setAntiAlias(true);
const char* comment = "HSL blend modes are correct when you see no circles in the squares.";
canvas->drawText(comment, strlen(comment), 10,10, label);
// 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;
SkColor expected;
} tests[] = {
{ SkBlendMode::kSrc, fg.getColor() },
{ SkBlendMode::kDst, bg.getColor() },
{ SkBlendMode::kHue, 0xffff00ff }, // bright magenta, H = 300°, S = 100%, L = 50%
{ SkBlendMode::kSaturation, 0xff55aa55 }, // a duller green, H = 120°, S = ~33%, L = 50%
{ SkBlendMode::kColor, 0xffaa55aa }, // a lighter fg, H = 300°, S = ~33%, L = 50%
{ SkBlendMode::kLuminosity, 0xff00bd00 }, // a darker bg, H = 120°, S = 100%, L = ~37%
};
for (auto test : tests) {
canvas->drawRect({20,20,80,80}, bg);
fg.setBlendMode(test.mode);
canvas->drawRect({20,20,80,80}, fg);
SkPaint expected;
expected.setColor(test.expected);
canvas->drawCircle(50,50, 20, expected);
const char* name = SkBlendMode_Name(test.mode);
canvas->drawText(name, strlen(name), 20,90, label);
canvas->translate(100,0);
}
}
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