tests/ColorSpaceXformTest.cpp

/*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "Resources.h"
#include "SkCodec.h"
#include "SkColorPriv.h"
#include "SkColorSpace.h"
#include "SkColorSpace_Base.h"
#include "SkColorSpaceXform.h"
#include "Test.h"

class ColorSpaceXformTest {
public:
    static std::unique_ptr<SkColorSpaceXform> CreateIdentityXform(const sk_sp<SkGammas>& gammas) {
        // Logically we can pass any matrix here.  For simplicty, pass I(), i.e. D50 XYZ gamut.
        sk_sp<SkColorSpace> space(new SkColorSpace_Base(nullptr, gammas, SkMatrix::I(), nullptr));
        return SkColorSpaceXform::New(space, space);
    }
};

static bool almost_equal(int x, int y) {
    return SkTAbs(x - y) <= 1;
}

static void test_identity_xform(skiatest::Reporter* r, const sk_sp<SkGammas>& gammas) {
    // Arbitrary set of 10 pixels
    constexpr int width = 10;
    constexpr uint32_t srcPixels[width] = {
            0xFFABCDEF, 0xFF146829, 0xFF382759, 0xFF184968, 0xFFDE8271,
            0xFF32AB52, 0xFF0383BC, 0xFF000102, 0xFFFFFFFF, 0xFFDDEEFF, };
    uint32_t dstPixels[width];

    // Create and perform an identity xform.
    std::unique_ptr<SkColorSpaceXform> xform = ColorSpaceXformTest::CreateIdentityXform(gammas);
    xform->applyTo8888(dstPixels, srcPixels, width);

    // Since the src->dst matrix is the identity, and the gamma curves match,
    // the pixels should be unchanged.
    for (int i = 0; i < width; i++) {
        REPORTER_ASSERT(r, almost_equal(((srcPixels[i] >>  0) & 0xFF),
                                        SkGetPackedR32(dstPixels[i])));
        REPORTER_ASSERT(r, almost_equal(((srcPixels[i] >>  8) & 0xFF),
                                        SkGetPackedG32(dstPixels[i])));
        REPORTER_ASSERT(r, almost_equal(((srcPixels[i] >> 16) & 0xFF),
                                        SkGetPackedB32(dstPixels[i])));
        REPORTER_ASSERT(r, almost_equal(((srcPixels[i] >> 24) & 0xFF),
                                        SkGetPackedA32(dstPixels[i])));
    }
}

DEF_TEST(ColorSpaceXform_TableGamma, r) {
    // Lookup-table based gamma curves
    SkGammaCurve red, green, blue;
    constexpr size_t tableSize = 10;
    red.fTable = std::unique_ptr<float[]>(new float[tableSize]);
    green.fTable = std::unique_ptr<float[]>(new float[tableSize]);
    blue.fTable = std::unique_ptr<float[]>(new float[tableSize]);
    red.fTableSize = green.fTableSize = blue.fTableSize = 10;
    red.fTable[0] = green.fTable[0] = blue.fTable[0] = 0.00f;
    red.fTable[1] = green.fTable[1] = blue.fTable[1] = 0.05f;
    red.fTable[2] = green.fTable[2] = blue.fTable[2] = 0.10f;
    red.fTable[3] = green.fTable[3] = blue.fTable[3] = 0.15f;
    red.fTable[4] = green.fTable[4] = blue.fTable[4] = 0.25f;
    red.fTable[5] = green.fTable[5] = blue.fTable[5] = 0.35f;
    red.fTable[6] = green.fTable[6] = blue.fTable[6] = 0.45f;
    red.fTable[7] = green.fTable[7] = blue.fTable[7] = 0.60f;
    red.fTable[8] = green.fTable[8] = blue.fTable[8] = 0.75f;
    red.fTable[9] = green.fTable[9] = blue.fTable[9] = 1.00f;
    sk_sp<SkGammas> gammas =
            sk_make_sp<SkGammas>(std::move(red), std::move(green), std::move(blue));
    test_identity_xform(r, gammas);
}

DEF_TEST(ColorSpaceXform_ParametricGamma, r) {
    // Parametric gamma curves
    SkGammaCurve red, green, blue;

    // Interval, switch xforms at 0.0031308f
    red.fD = green.fD = blue.fD = 0.04045f;

    // First equation:
    red.fE = green.fE = blue.fE = 1.0f / 12.92f;

    // Second equation:
    // Note that the function is continuous (it's actually sRGB).
    red.fA = green.fA = blue.fA = 1.0f / 1.055f;
    red.fB = green.fB = blue.fB = 0.055f / 1.055f;
    red.fC = green.fC = blue.fC = 0.0f;
    red.fG = green.fG = blue.fG = 2.4f;
    sk_sp<SkGammas> gammas =
            sk_make_sp<SkGammas>(std::move(red), std::move(green), std::move(blue));
    test_identity_xform(r, gammas);
}

DEF_TEST(ColorSpaceXform_ExponentialGamma, r) {
    // Exponential gamma curves
    SkGammaCurve red, green, blue;
    red.fValue = green.fValue = blue.fValue = 1.4f;
    sk_sp<SkGammas> gammas =
            sk_make_sp<SkGammas>(std::move(red), std::move(green), std::move(blue));
    test_identity_xform(r, gammas);
}