skia2/tests/ColorTest.cpp

#include "Test.h"
#include "SkColor.h"
#include "SkUnPreMultiply.h"

static void test_premul(skiatest::Reporter* reporter) {
    for (int a = 0; a <= 255; a++) {
        for (int x = 0; x <= 255; x++) {
            SkColor c0 = SkColorSetARGB(a, x, x, x);
            SkPMColor p0 = SkPreMultiplyColor(c0);

            SkColor c1 = SkUnPreMultiply::PMColorToColor(p0);
            SkPMColor p1 = SkPreMultiplyColor(c1);

            // we can't promise that c0 == c1, since c0 -> p0 is a many to one
            // function, however, we can promise that p0 -> c1 -> p1 : p0 == p1
            REPORTER_ASSERT(reporter, p0 == p1);

            {
                int ax = SkMulDiv255Ceiling(x, a);
                REPORTER_ASSERT(reporter, ax <= a);
            }
        }
    }
}


static void TestColor(skiatest::Reporter* reporter) {
    test_premul(reporter);
}

#include "TestClassDef.h"
DEFINE_TESTCLASS("Color", ColorTestClass, TestColor)