C++ SkAlphaMulQ函数代码示例

void SkARGB32_Blitter::blitV(int x, int y, int height, SkAlpha alpha) {
    if (alpha == 0 || fSrcA == 0) {
        return;
    }

    uint32_t* device = fDevice.getAddr32(x, y);
    uint32_t  color = fPMColor;

    if (alpha != 255) {
        color = SkAlphaMulQ(color, SkAlpha255To256(alpha));
    }

    unsigned dst_scale = 255 - SkGetPackedA32(color);
    uint32_t prevDst = ~device[0];
    uint32_t result  SK_INIT_TO_AVOID_WARNING;
    uint32_t rowBytes = fDevice.rowBytes();

    while (--height >= 0) {
        uint32_t dst = device[0];
        if (dst != prevDst) {
            result = color + SkAlphaMulQ(dst, dst_scale);
            prevDst = dst;
        }
        device[0] = result;
        device = (uint32_t*)((char*)device + rowBytes);
    }
}

void SkARGB32_Blitter::blitAntiH(int x, int y, const SkAlpha antialias[],
                                 const int16_t runs[]) {
    if (fSrcA == 0) {
        return;
    }

    uint32_t    color = fPMColor;
    uint32_t*   device = fDevice.getAddr32(x, y);
    unsigned    opaqueMask = fSrcA; // if fSrcA is 0xFF, then we will catch the fast opaque case

    for (;;) {
        int count = runs[0];
        SkASSERT(count >= 0);
        if (count <= 0) {
            return;
        }
        unsigned aa = antialias[0];
        if (aa) {
            if ((opaqueMask & aa) == 255) {
                sk_memset32(device, color, count);
            } else {
                uint32_t sc = SkAlphaMulQ(color, aa);
                unsigned dst_scale = 255 - SkGetPackedA32(sc);
                int n = count;
                do {
                    --n;
                    device[n] = sc + SkAlphaMulQ(device[n], dst_scale);
                } while (n > 0);
            }
        }
        runs += count;
        antialias += count;
        device += count;
    }
}

void SkComposeShader::ComposeShaderContext::shadeSpan(int x, int y, SkPMColor result[], int count) {
    SkShader::Context* shaderContextA = fShaderContextA;
    SkShader::Context* shaderContextB = fShaderContextB;
    SkBlendMode        mode = static_cast<const SkComposeShader&>(fShader).fMode;
    unsigned           scale = SkAlpha255To256(this->getPaintAlpha());

    SkPMColor   tmp[TMP_COLOR_COUNT];

    SkXfermode* xfer = SkXfermode::Peek(mode);
    if (nullptr == xfer) {   // implied SRC_OVER
        // TODO: when we have a good test-case, should use SkBlitRow::Proc32
        // for these loops
        do {
            int n = count;
            if (n > TMP_COLOR_COUNT) {
                n = TMP_COLOR_COUNT;
            }

            shaderContextA->shadeSpan(x, y, result, n);
            shaderContextB->shadeSpan(x, y, tmp, n);

            if (256 == scale) {
                for (int i = 0; i < n; i++) {
                    result[i] = SkPMSrcOver(tmp[i], result[i]);
                }
            } else {
                for (int i = 0; i < n; i++) {
                    result[i] = SkAlphaMulQ(SkPMSrcOver(tmp[i], result[i]),
                                            scale);
                }
            }

            result += n;
            x += n;
            count -= n;
        } while (count > 0);
    } else {    // use mode for the composition
        do {
            int n = count;
            if (n > TMP_COLOR_COUNT) {
                n = TMP_COLOR_COUNT;
            }

            shaderContextA->shadeSpan(x, y, result, n);
            shaderContextB->shadeSpan(x, y, tmp, n);
            xfer->xfer32(result, tmp, n, nullptr);

            if (256 != scale) {
                for (int i = 0; i < n; i++) {
                    result[i] = SkAlphaMulQ(result[i], scale);
                }
            }

            result += n;
            x += n;
            count -= n;
        } while (count > 0);
    }
}

void SkComposeShader::shadeSpan(int x, int y, SkPMColor result[], int count) {
    SkShader*   shaderA = fShaderA;
    SkShader*   shaderB = fShaderB;
    SkXfermode* mode = fMode;
    unsigned    scale = SkAlpha255To256(this->getPaintAlpha());

    SkPMColor   tmp[TMP_COLOR_COUNT];

    if (NULL == mode) {   // implied SRC_OVER
        // TODO: when we have a good test-case, should use SkBlitRow::Proc32
        // for these loops
        do {
            int n = count;
            if (n > TMP_COLOR_COUNT) {
                n = TMP_COLOR_COUNT;
            }

            shaderA->shadeSpan(x, y, result, n);
            shaderB->shadeSpan(x, y, tmp, n);

            if (256 == scale) {
                for (int i = 0; i < n; i++) {
                    result[i] = SkPMSrcOver(tmp[i], result[i]);
                }
            } else {
                for (int i = 0; i < n; i++) {
                    result[i] = SkAlphaMulQ(SkPMSrcOver(tmp[i], result[i]),
                                            scale);
                }
            }

            result += n;
            x += n;
            count -= n;
        } while (count > 0);
    } else {    // use mode for the composition
        do {
            int n = count;
            if (n > TMP_COLOR_COUNT) {
                n = TMP_COLOR_COUNT;
            }

            shaderA->shadeSpan(x, y, result, n);
            shaderB->shadeSpan(x, y, tmp, n);
            mode->xfer32(result, tmp, n, NULL);

            if (256 == scale) {
                for (int i = 0; i < n; i++) {
                    result[i] = SkAlphaMulQ(result[i], scale);
                }
            }

            result += n;
            x += n;
            count -= n;
        } while (count > 0);
    }
}

//  kSrcOver_Mode,  //!< [Sa + Da - Sa*Da, Sc + (1 - Sa)*Dc] 
static SkPMColor srcover_modeproc(SkPMColor src, SkPMColor dst) {
#if 0
    // this is the old, more-correct way, but it doesn't guarantee that dst==255
    // will always stay opaque
    return src + SkAlphaMulQ(dst, SkAlpha255To256(255 - SkGetPackedA32(src)));
#else
    // this is slightly faster, but more importantly guarantees that dst==255
    // will always stay opaque
    return src + SkAlphaMulQ(dst, 256 - SkGetPackedA32(src));
#endif
}

void SkARGB32_Blitter::blitAntiH(int x, int y, const SkAlpha antialias[],
                                 const int16_t runs[]) {
    if (fSrcA == 0) {
        return;
    }

    uint32_t    color = fPMColor;
    uint32_t*   device = fDevice.writable_addr32(x, y);
    unsigned    opaqueMask = fSrcA; // if fSrcA is 0xFF, then we will catch the fast opaque case

    for (;;) {
        int count = runs[0];
        SkASSERT(count >= 0);
        if (count <= 0) {
            return;
        }
        unsigned aa = antialias[0];
        if (aa) {
            if ((opaqueMask & aa) == 255) {
                sk_memset32(device, color, count);
            } else {
                uint32_t sc = SkAlphaMulQ(color, SkAlpha255To256(aa));
                SkBlitRow::Color32(device, device, count, sc);
            }
        }
        runs += count;
        antialias += count;
        device += count;
    }
}

void SkARGB32_Black_Blitter::blitAntiH(int x, int y, const SkAlpha antialias[],
                                       const int16_t runs[]) {
    uint32_t*   device = fDevice.getAddr32(x, y);
    SkPMColor   black = (SkPMColor)(SK_A32_MASK << SK_A32_SHIFT);

    for (;;) {
        int count = runs[0];
        SkASSERT(count >= 0);
        if (count <= 0) {
            return;
        }
        unsigned aa = antialias[0];
        if (aa) {
            if (aa == 255) {
                sk_memset32(device, black, count);
            } else {
                SkPMColor src = aa << SK_A32_SHIFT;
                unsigned dst_scale = 256 - aa;
                int n = count;
                do {
                    --n;
                    device[n] = src + SkAlphaMulQ(device[n], dst_scale);
                } while (n > 0);
            }
        }
        runs += count;
        antialias += count;
        device += count;
    }
}

// extract the result vertices and indices from the GrAAConvexTessellator
static void extract_verts(const GrAAConvexTessellator& tess,
                          void* vertices,
                          size_t vertexStride,
                          GrColor color,
                          uint16_t firstIndex,
                          uint16_t* idxs,
                          bool tweakAlphaForCoverage) {
    intptr_t verts = reinterpret_cast<intptr_t>(vertices);

    for (int i = 0; i < tess.numPts(); ++i) {
        *((SkPoint*)((intptr_t)verts + i * vertexStride)) = tess.point(i);
    }

    // Make 'verts' point to the colors
    verts += sizeof(SkPoint);
    for (int i = 0; i < tess.numPts(); ++i) {
        if (tweakAlphaForCoverage) {
            SkASSERT(SkScalarRoundToInt(255.0f * tess.coverage(i)) <= 255);
            unsigned scale = SkScalarRoundToInt(255.0f * tess.coverage(i));
            GrColor scaledColor = (0xff == scale) ? color : SkAlphaMulQ(color, scale);
            *reinterpret_cast<GrColor*>(verts + i * vertexStride) = scaledColor;
        } else {
            *reinterpret_cast<GrColor*>(verts + i * vertexStride) = color;
            *reinterpret_cast<float*>(verts + i * vertexStride + sizeof(GrColor)) = 
                    tess.coverage(i);
        }
    }

    for (int i = 0; i < tess.numIndices(); ++i) {
        idxs[i] = tess.index(i) + firstIndex;
    }
}

void SkTransparentShader::TransparentShaderContext::shadeSpan(int x, int y, SkPMColor span[],
                                                              int count) {
    unsigned scale = SkAlpha255To256(this->getPaintAlpha());

    switch (fDevice->colorType()) {
        case kN32_SkColorType:
            if (scale == 256) {
                SkPMColor* src = fDevice->getAddr32(x, y);
                if (src != span) {
                    memcpy(span, src, count * sizeof(SkPMColor));
                }
            } else {
                const SkPMColor* src = fDevice->getAddr32(x, y);
                for (int i = count - 1; i >= 0; --i) {
                    span[i] = SkAlphaMulQ(src[i], scale);
                }
            }
            break;
        case kRGB_565_SkColorType: {
            const uint16_t* src = fDevice->getAddr16(x, y);
            if (scale == 256) {
                for (int i = count - 1; i >= 0; --i) {
                    span[i] = SkPixel16ToPixel32(src[i]);
                }
            } else {
                unsigned alpha = this->getPaintAlpha();
                for (int i = count - 1; i >= 0; --i) {
                    uint16_t c = src[i];
                    unsigned r = SkPacked16ToR32(c);
                    unsigned g = SkPacked16ToG32(c);
                    unsigned b = SkPacked16ToB32(c);

                    span[i] = SkPackARGB32( alpha,
                                            SkAlphaMul(r, scale),
                                            SkAlphaMul(g, scale),
                                            SkAlphaMul(b, scale));
                }
            }
            break;
        }
        case kAlpha_8_SkColorType: {
            const uint8_t* src = fDevice->getAddr8(x, y);
            if (scale == 256) {
                for (int i = count - 1; i >= 0; --i) {
                    span[i] = SkPackARGB32(src[i], 0, 0, 0);
                }
            } else {
                for (int i = count - 1; i >= 0; --i) {
                    span[i] = SkPackARGB32(SkAlphaMul(src[i], scale), 0, 0, 0);
                }
            }
            break;
        }
        default:
            SkDEBUGFAIL("colorType not supported as a destination device");
            break;
    }
}

void SkARGB32_Blitter::blitV(int x, int y, int height, SkAlpha alpha) {
    if (alpha == 0 || fSrcA == 0) {
        return;
    }

    uint32_t* device = fDevice.getAddr32(x, y);
    uint32_t  color = fPMColor;

    if (alpha != 255) {
        color = SkAlphaMulQ(color, SkAlpha255To256(alpha));
    }

    unsigned dst_scale = 255 - SkGetPackedA32(color);
    uint32_t rowBytes = fDevice.rowBytes();
    while (--height >= 0) {
        device[0] = color + SkAlphaMulQ(device[0], dst_scale);
        device = (uint32_t*)((char*)device + rowBytes);
    }
}

    virtual void xfer32(SK_RESTRICT SkPMColor dst[],
                        const SK_RESTRICT SkPMColor[], int count,
                        const SK_RESTRICT SkAlpha aa[]) {
        SkASSERT(dst && count >= 0);

        if (NULL == aa) {
            memset(dst, 0, count << 2);
        } else {
            for (int i = count - 1; i >= 0; --i) {
                unsigned a = aa[i];
                if (0xFF == a) {
                    dst[i] = 0;
                } else if (a != 0) {
                    dst[i] = SkAlphaMulQ(dst[i], SkAlpha255To256(255 - a));
                }
            }
        }
    }

//  kDstOut_Mode,   //!< [Da * (1 - Sa), Dc * (1 - Sa)]
static SkPMColor dstout_modeproc(SkPMColor src, SkPMColor dst) {
    return SkAlphaMulQ(dst, SkAlpha255To256(255 - SkGetPackedA32(src)));
}

//  kSrcIn_Mode,    //!< [Sa * Da, Sc * Da]
static SkPMColor srcin_modeproc(SkPMColor src, SkPMColor dst) {
    return SkAlphaMulQ(src, SkAlpha255To256(SkGetPackedA32(dst)));
}

//  kDstOver_Mode,  //!< [Sa + Da - Sa*Da, Dc + (1 - Da)*Sc]
static SkPMColor dstover_modeproc(SkPMColor src, SkPMColor dst) {
    // this is the reverse of srcover, just flipping src and dst
    // see srcover's comment about the 256 for opaqueness guarantees
    return dst + SkAlphaMulQ(src, 256 - SkGetPackedA32(dst));
}

    void generateAAStrokeRectGeometry(void* vertices,
                                      size_t offset,
                                      size_t vertexStride,
                                      int outerVertexNum,
                                      int innerVertexNum,
                                      GrColor color,
                                      const SkRect& devOutside,
                                      const SkRect& devOutsideAssist,
                                      const SkRect& devInside,
                                      bool miterStroke,
                                      bool tweakAlphaForCoverage) const {
        intptr_t verts = reinterpret_cast<intptr_t>(vertices) + offset;

        // We create vertices for four nested rectangles. There are two ramps from 0 to full
        // coverage, one on the exterior of the stroke and the other on the interior.
        // The following pointers refer to the four rects, from outermost to innermost.
        SkPoint* fan0Pos = reinterpret_cast<SkPoint*>(verts);
        SkPoint* fan1Pos = reinterpret_cast<SkPoint*>(verts + outerVertexNum * vertexStride);
        SkPoint* fan2Pos = reinterpret_cast<SkPoint*>(verts + 2 * outerVertexNum * vertexStride);
        SkPoint* fan3Pos = reinterpret_cast<SkPoint*>(verts +
                                                      (2 * outerVertexNum + innerVertexNum) *
                                                      vertexStride);

    #ifndef SK_IGNORE_THIN_STROKED_RECT_FIX
        // TODO: this only really works if the X & Y margins are the same all around
        // the rect (or if they are all >= 1.0).
        SkScalar inset = SkMinScalar(SK_Scalar1, devOutside.fRight - devInside.fRight);
        inset = SkMinScalar(inset, devInside.fLeft - devOutside.fLeft);
        inset = SkMinScalar(inset, devInside.fTop - devOutside.fTop);
        if (miterStroke) {
            inset = SK_ScalarHalf * SkMinScalar(inset, devOutside.fBottom - devInside.fBottom);
        } else {
            inset = SK_ScalarHalf * SkMinScalar(inset, devOutsideAssist.fBottom -
                                                       devInside.fBottom);
        }
        SkASSERT(inset >= 0);
    #else
        SkScalar inset = SK_ScalarHalf;
    #endif

        if (miterStroke) {
            // outermost
            set_inset_fan(fan0Pos, vertexStride, devOutside, -SK_ScalarHalf, -SK_ScalarHalf);
            // inner two
            set_inset_fan(fan1Pos, vertexStride, devOutside,  inset,  inset);
            set_inset_fan(fan2Pos, vertexStride, devInside,  -inset, -inset);
            // innermost
            set_inset_fan(fan3Pos, vertexStride, devInside,   SK_ScalarHalf,  SK_ScalarHalf);
        } else {
            SkPoint* fan0AssistPos = reinterpret_cast<SkPoint*>(verts + 4 * vertexStride);
            SkPoint* fan1AssistPos = reinterpret_cast<SkPoint*>(verts +
                                                                (outerVertexNum + 4) *
                                                                vertexStride);
            // outermost
            set_inset_fan(fan0Pos, vertexStride, devOutside, -SK_ScalarHalf, -SK_ScalarHalf);
            set_inset_fan(fan0AssistPos, vertexStride, devOutsideAssist, -SK_ScalarHalf,
                          -SK_ScalarHalf);
            // outer one of the inner two
            set_inset_fan(fan1Pos, vertexStride, devOutside,  inset,  inset);
            set_inset_fan(fan1AssistPos, vertexStride, devOutsideAssist,  inset,  inset);
            // inner one of the inner two
            set_inset_fan(fan2Pos, vertexStride, devInside,  -inset, -inset);
            // innermost
            set_inset_fan(fan3Pos, vertexStride, devInside,   SK_ScalarHalf,  SK_ScalarHalf);
        }

        // Make verts point to vertex color and then set all the color and coverage vertex attrs
        // values. The outermost rect has 0 coverage
        verts += sizeof(SkPoint);
        for (int i = 0; i < outerVertexNum; ++i) {
            if (tweakAlphaForCoverage) {
                *reinterpret_cast<GrColor*>(verts + i * vertexStride) = 0;
            } else {
                *reinterpret_cast<GrColor*>(verts + i * vertexStride) = color;
                *reinterpret_cast<float*>(verts + i * vertexStride + sizeof(GrColor)) = 0;
            }
        }

        // scale is the coverage for the the inner two rects.
        int scale;
        if (inset < SK_ScalarHalf) {
            scale = SkScalarFloorToInt(512.0f * inset / (inset + SK_ScalarHalf));
            SkASSERT(scale >= 0 && scale <= 255);
        } else {
            scale = 0xff;
        }

        float innerCoverage = GrNormalizeByteToFloat(scale);
        GrColor scaledColor = (0xff == scale) ? color : SkAlphaMulQ(color, scale);

        verts += outerVertexNum * vertexStride;
        for (int i = 0; i < outerVertexNum + innerVertexNum; ++i) {
            if (tweakAlphaForCoverage) {
                *reinterpret_cast<GrColor*>(verts + i * vertexStride) = scaledColor;
            } else {
                *reinterpret_cast<GrColor*>(verts + i * vertexStride) = color;
                *reinterpret_cast<float*>(verts + i * vertexStride + sizeof(GrColor)) =
                        innerCoverage;
            }
        }
//.........这里部分代码省略.........