C++ SkPreMultiplyColor函数代码示例

    /**
     * Create a red & green stripes on black texture
     */
    void createTexture() {
        if (fTextureCreated) {
            return;
        }

        static const int xSize = 16;
        static const int ySize = 16;

        fTexture.allocN32Pixels(xSize, ySize);
        SkPMColor* addr = fTexture.getAddr32(0, 0);

        for (int y = 0; y < ySize; ++y) {
            for (int x = 0; x < xSize; ++x) {
                addr[y*xSize+x] = SkPreMultiplyColor(SK_ColorBLACK);

                if ((y % 5) == 0) {
                    addr[y*xSize+x] = SkPreMultiplyColor(SK_ColorRED);
                }
                if ((x % 7) == 0) {
                    addr[y*xSize+x] = SkPreMultiplyColor(SK_ColorGREEN);
                }
            }
        }

        fTextureCreated = true;
    }

static bool compare_procs(SkXfermodeProc proc32, SkXfermodeProc4f proc4f) {
    const float kTolerance = 1.0f / 255;

    const SkColor colors[] = {
        0, 0xFF000000, 0xFFFFFFFF, 0x80FF0000
    };

    for (auto s32 : colors) {
        SkPMColor s_pm32 = SkPreMultiplyColor(s32);
        SkPM4f    s_pm4f = SkColor4f::FromColor(s32).premul();
        for (auto d32 : colors) {
            SkPMColor d_pm32 = SkPreMultiplyColor(d32);
            SkPM4f    d_pm4f = SkColor4f::FromColor(d32).premul();

            SkPMColor r32 = proc32(s_pm32, d_pm32);
            SkPM4f    r4f = proc4f(s_pm4f, d_pm4f);

            SkPM4f r32_4f = SkPM4f::FromPMColor(r32);
            if (!nearly_equal(r4f, r32_4f, kTolerance)) {
                return false;
            }
        }
    }
    return true;
}

/** Create a black and white checked bitmap with 2 1-pixel rings around the outside edge.
    The inner ring is red and the outer ring is blue. */
static bool make_ringed_color_bitmap(TestPixels* result, int width, int height) {
    const SkPMColor kBlue  = SkPreMultiplyColor(SK_ColorBLUE);
    const SkPMColor kRed   = SkPreMultiplyColor(SK_ColorRED);
    const SkPMColor kBlack = SkPreMultiplyColor(SK_ColorBLACK);
    const SkPMColor kWhite = SkPreMultiplyColor(SK_ColorWHITE);
    return make_ringed_bitmap<SkPMColor>(result, width, height, kN32_SkColorType,
                                         kPremul_SkAlphaType, kBlue, kRed, kBlack, kWhite);
}

	OvalTestView() {
        fSize.set(SK_Scalar1, SK_Scalar1);

        fBitmap.setConfig(SkBitmap::kARGB_8888_Config, kILimit, kILimit);
        fBitmap.allocPixels();

        fInsideColor = SkPreMultiplyColor(SK_ColorRED);
        fOutsideColor = SkPreMultiplyColor(SK_ColorGREEN);
    }

/** Make the color version of the oversized texture-backed bitmap */
static bool make_ringed_oversized_color_texture_bitmap(GrContext* ctx, TestPixels* result,
                                                       int width, int height) {
    static const SkPMColor kBlue = SkPreMultiplyColor(SK_ColorBLUE);
    static const SkPMColor kRed = SkPreMultiplyColor(SK_ColorRED);
    static const SkPMColor kBlack = SkPreMultiplyColor(SK_ColorBLACK);
    static const SkPMColor kWhite = SkPreMultiplyColor(SK_ColorWHITE);
    static const SkPMColor kGreen = SkPreMultiplyColor(SK_ColorGREEN);
    return make_oversized_texture_bitmap<SkPMColor>(
        ctx, result, width, height, kSkia8888_GrPixelConfig, kBlue, kRed, kBlack, kWhite, kGreen);
}

DEF_GPUTEST_FOR_NATIVE_CONTEXT(SkImage_NewFromTexture, reporter, context) {
    GrTextureProvider* provider = context->textureProvider();
    const int w = 10;
    const int h = 10;
    SkPMColor storage[w * h];
    const SkPMColor expected0 = SkPreMultiplyColor(SK_ColorRED);
    sk_memset32(storage, expected0, w * h);
    GrSurfaceDesc desc;
    desc.fFlags = kRenderTarget_GrSurfaceFlag;  // needs to be a rendertarget for readpixels();
    desc.fOrigin = kDefault_GrSurfaceOrigin;
    desc.fWidth = w;
    desc.fHeight = h;
    desc.fConfig = kSkia8888_GrPixelConfig;
    desc.fSampleCnt = 0;
    SkAutoTUnref<GrTexture> tex(provider->createTexture(desc, false, storage, w * 4));
    if (!tex) {
        REPORTER_ASSERT(reporter, false);
        return;
    }

    GrBackendTextureDesc backendDesc;
    backendDesc.fConfig = kSkia8888_GrPixelConfig;
    backendDesc.fFlags = kRenderTarget_GrBackendTextureFlag;
    backendDesc.fWidth = w;
    backendDesc.fHeight = h;
    backendDesc.fSampleCnt = 0;
    backendDesc.fTextureHandle = tex->getTextureHandle();
    TextureReleaseChecker releaseChecker;
    SkAutoTUnref<SkImage> refImg(
        SkImage::NewFromTexture(context, backendDesc, kPremul_SkAlphaType,
                                TextureReleaseChecker::Release, &releaseChecker));
    SkAutoTUnref<SkImage> cpyImg(SkImage::NewFromTextureCopy(context, backendDesc,
                                                             kPremul_SkAlphaType));

    check_image_color(reporter, refImg, expected0);
    check_image_color(reporter, cpyImg, expected0);

    // Now lets jam new colors into our "external" texture, and see if the images notice
    const SkPMColor expected1 = SkPreMultiplyColor(SK_ColorBLUE);
    sk_memset32(storage, expected1, w * h);
    tex->writePixels(0, 0, w, h, kSkia8888_GrPixelConfig, storage, GrContext::kFlushWrites_PixelOp);

    // The cpy'd one should still see the old color
#if 0
    // There is no guarantee that refImg sees the new color. We are free to have made a copy. Our
    // write pixels call violated the contract with refImg and refImg is now undefined.
    check_image_color(reporter, refImg, expected1);
#endif
    check_image_color(reporter, cpyImg, expected0);

    // Now exercise the release proc
    REPORTER_ASSERT(reporter, 0 == releaseChecker.fReleaseCount);
    refImg.reset(nullptr); // force a release of the image
    REPORTER_ASSERT(reporter, 1 == releaseChecker.fReleaseCount);
}

static SkColor xferColor(SkColor src, SkColor dst, SkXfermode::Mode mode) {
    switch (mode) {
        case SkXfermode::kSrc_Mode:
            return src;
        case SkXfermode::kDst_Mode:
            return dst;
        default: {
            SkPMColor pmS = SkPreMultiplyColor(src);
            SkPMColor pmD = SkPreMultiplyColor(dst);
            SkPMColor result = SkXfermode::GetProc(mode)(pmS, pmD);
            return SkUnPreMultiply::PMColorToColor(result);
        }
    }
}

static inline void test_fast_interp(skiatest::Reporter* reporter) {
    SkRandom r;

    U8CPU a0 = 0;
    U8CPU a255 = 255;
    for (int i = 0; i < 200; i++) {
        SkColor colorSrc = r.nextU();
        SkColor colorDst = r.nextU();
        SkPMColor src = SkPreMultiplyColor(colorSrc);
        SkPMColor dst = SkPreMultiplyColor(colorDst);

        REPORTER_ASSERT(reporter, SkFastFourByteInterp(src, dst, a0) == dst);
        REPORTER_ASSERT(reporter, SkFastFourByteInterp(src, dst, a255) == src);
    }
}

static void make_bm(SkBitmap* bm) {
    const SkPMColor colors[] = {
        SkPreMultiplyColor(SK_ColorRED), SkPreMultiplyColor(SK_ColorGREEN),
        SkPreMultiplyColor(SK_ColorBLUE), SkPreMultiplyColor(SK_ColorWHITE)
    };
    SkColorTable* ctable = new SkColorTable(colors, 4);
    bm->allocPixels(SkImageInfo::Make(2, 2, kIndex_8_SkColorType,
                                      kOpaque_SkAlphaType),
                    nullptr, ctable);
    ctable->unref();

    *bm->getAddr8(0, 0) = 0;
    *bm->getAddr8(1, 0) = 1;
    *bm->getAddr8(0, 1) = 2;
    *bm->getAddr8(1, 1) = 3;
}

DEF_TEST(Color4f_colorfilter, reporter) {
    struct {
        SkColorFilter* (*fFact)();
        bool           fSupports4f;
        const char*    fName;
    } recs[] = {
        { make_mode_cf,     true, "mode" },
        { make_mx_cf,       true, "matrix" },
        { make_compose_cf,  true, "compose" },
    };

    // prepare the src
    const int N = 100;
    SkPMColor src4b[N];
    SkPM4f    src4f[N];
    SkRandom rand;
    for (int i = 0; i < N; ++i) {
        src4b[i] = SkPreMultiplyColor(rand.nextU());
        src4f[i] = SkPM4f::FromPMColor(src4b[i]);
    }
    // confirm that our srcs are (nearly) equal
    REPORTER_ASSERT(reporter, compare_spans(src4f, src4b, N));

    for (const auto& rec : recs) {
        SkAutoTUnref<SkColorFilter> filter(rec.fFact());
        SkPMColor dst4b[N];
        filter->filterSpan(src4b, N, dst4b);
        SkPM4f dst4f[N];
        filter->filterSpan4f(src4f, N, dst4f);
        REPORTER_ASSERT(reporter, compare_spans(dst4f, dst4b, N));
    }
}

static SkShader* createChecker() {
//    SkColor colors[] = { 0xFFFDFDFD, 0xFFF4F4F4 };
    SkColor colors[] = { 0xFFFFFFFF, 0xFFFFFFFF };
    SkBitmap bm;
    bm.allocN32Pixels(2, 2);
    bm.lockPixels();
    *bm.getAddr32(0, 0) = *bm.getAddr32(1, 1) = SkPreMultiplyColor(colors[0]);
    *bm.getAddr32(0, 1) = *bm.getAddr32(1, 0) = SkPreMultiplyColor(colors[1]);
    SkShader* s = SkShader::CreateBitmapShader(bm, SkShader::kRepeat_TileMode,
                                               SkShader::kRepeat_TileMode);

    SkMatrix m;
    m.setScale(12, 12);
    s->setLocalMatrix(m);
    return s;
}

void SkGL::SetColor(SkColor c) {
    SkPMColor pm = SkPreMultiplyColor(c);
    gl_pmcolor(SkGetPackedR32(pm),
               SkGetPackedG32(pm),
               SkGetPackedB32(pm),
               SkGetPackedA32(pm));
}

SkARGB4444_Blitter::SkARGB4444_Blitter(const SkBitmap& device,
                                   const SkPaint& paint) : INHERITED(device) {
    // cache premultiplied versions in 4444
    SkPMColor c = SkPreMultiplyColor(paint.getColor());
    fPMColor16 = SkPixel32ToPixel4444(c);
    if (paint.isDither()) {
        fPMColor16Other = SkDitherPixel32To4444(c);
    } else {
        fPMColor16Other = fPMColor16;
    }

    // cache raw versions in 4444
    fRawColor16 = SkPackARGB4444(0xFF >> 4, SkColorGetR(c) >> 4,
                                 SkColorGetG(c) >> 4, SkColorGetB(c) >> 4);
    if (paint.isDither()) {
        fRawColor16Other = SkDitherARGB32To4444(0xFF, SkColorGetR(c),
                                                SkColorGetG(c), SkColorGetB(c));
    } else {
        fRawColor16Other = fRawColor16;
    }

    fScale16 = SkAlpha15To16(SkGetPackedA4444(fPMColor16Other));
    if (16 == fScale16) {
        // force the original to also be opaque
        fPMColor16 |= (0xF << SK_A4444_SHIFT);
    }
}

static void FromColor_D32(void* dst, const SkColor src[], int width,
                          int, int) {
    SkPMColor* d = (SkPMColor*)dst;

    for (int i = 0; i < width; i++) {
        *d++ = SkPreMultiplyColor(*src++);
    }
}

static inline 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);
            }
        }
    }
}