C++ SkShader类代码示例

    CameraView() {
        fRX = fRY = fRZ = 0;
        fShaderIndex = 0;
        fFrontFace = false;

        for (int i = 0;; i++) {
            SkString str;
            str.printf("/skimages/elephant%d.jpeg", i);
            SkBitmap bm;
            if (SkImageDecoder::DecodeFile(str.c_str(), &bm)) {
                SkShader* s = SkShader::CreateBitmapShader(bm,
                                                           SkShader::kClamp_TileMode,
                                                           SkShader::kClamp_TileMode);

                SkRect src = { 0, 0, SkIntToScalar(bm.width()), SkIntToScalar(bm.height()) };
                SkRect dst = { -150, -150, 150, 150 };
                SkMatrix matrix;
                matrix.setRectToRect(src, dst, SkMatrix::kFill_ScaleToFit);
                s->setLocalMatrix(matrix);
                *fShaders.append() = s;
            } else {
                break;
            }
        }
        this->setBGColor(0xFFDDDDDD);
    }

    virtual void onDraw(SkCanvas* canvas) {

        SkPoint pts[2] = {
            { 0, 0 },
            { SkIntToScalar(100), SkIntToScalar(100) }
        };
        SkShader::TileMode tm = SkShader::kClamp_TileMode;
        SkRect r = { 0, 0, SkIntToScalar(100), SkIntToScalar(100) };
        SkPaint paint;
        paint.setAntiAlias(true);

        canvas->translate(SkIntToScalar(20), SkIntToScalar(20));
        for (size_t i = 0; i < SK_ARRAY_COUNT(gGradData); i++) {
            canvas->save();
            for (size_t j = 0; j < SK_ARRAY_COUNT(gGradMakers); j++) {
                SkMatrix scale = SkMatrix::I();

                if (i == 5) { // if the clamp case
                    scale.setScale(0.5f, 0.5f);
                    scale.postTranslate(25.f, 25.f);
                }

                SkShader* shader = gGradMakers[j](pts, gGradData[i], tm, scale);

                paint.setShader(shader);
                canvas->drawRect(r, paint);
                shader->unref();
                canvas->translate(0, SkIntToScalar(120));
            }
            canvas->restore();
            canvas->translate(SkIntToScalar(120), 0);
        }
    }

static void gradient_slide(SkCanvas* canvas) {
    SkPoint pts[2] = {
        { 0, 0 },
        { SkIntToScalar(100), SkIntToScalar(100) }
    };
    SkShader::TileMode tm = SkShader::kClamp_TileMode;
    SkRect r = { 0, 0, SkIntToScalar(100), SkIntToScalar(100) };
    SkPaint paint;
    paint.setAntiAlias(true);
    paint.setDither(true);

    canvas->translate(SkIntToScalar(20), SkIntToScalar(10));
    for (size_t i = 0; i < SK_ARRAY_COUNT(gGradData); i++) {
        canvas->save();
        for (size_t j = 0; j < SK_ARRAY_COUNT(gGradMakers); j++) {
            SkShader* shader = gGradMakers[j](pts, gGradData[i], tm);
            paint.setShader(shader);
            canvas->drawRect(r, paint);
            shader->unref();
            canvas->translate(0, SkIntToScalar(120));
        }
        canvas->restore();
        canvas->translate(SkIntToScalar(120), 0);
    }
}

SkPDFShader::State::State(const SkShader& shader,
                          const SkMatrix& canvasTransform, const SkIRect& bbox)
        : fCanvasTransform(canvasTransform),
          fBBox(bbox),
          fPixelGeneration(0) {
    fInfo.fColorCount = 0;
    fInfo.fColors = NULL;
    fInfo.fColorOffsets = NULL;
    fShaderTransform = shader.getLocalMatrix();
    fImageTileModes[0] = fImageTileModes[1] = SkShader::kClamp_TileMode;

    fType = shader.asAGradient(&fInfo);

    if (fType == SkShader::kNone_GradientType) {
        SkShader::BitmapType bitmapType;
        SkMatrix matrix;
        bitmapType = shader.asABitmap(&fImage, &matrix, fImageTileModes);
        if (bitmapType != SkShader::kDefault_BitmapType) {
            fImage.reset();
            return;
        }
        SkASSERT(matrix.isIdentity());
        fPixelGeneration = fImage.getGenerationID();
    } else {
        AllocateGradientInfoStorage();
        shader.asAGradient(&fInfo);
    }
}

/* Hit a few SkPicture::Analysis cases not handled elsewhere. */
static void test_analysis(skiatest::Reporter* reporter) {
    SkPictureRecorder recorder;

    SkCanvas* canvas = recorder.beginRecording(100, 100);
    {
        canvas->drawRect(SkRect::MakeWH(10, 10), SkPaint ());
    }
    SkAutoTUnref<SkPicture> picture(recorder.endRecording());
    REPORTER_ASSERT(reporter, !picture->willPlayBackBitmaps());

    canvas = recorder.beginRecording(100, 100);
    {
        SkPaint paint;
        // CreateBitmapShader is too smart for us; an empty (or 1x1) bitmap shader
        // gets optimized into a non-bitmap form, so we create a 2x2 bitmap here.
        SkBitmap bitmap;
        bitmap.allocPixels(SkImageInfo::MakeN32Premul(2, 2));
        bitmap.eraseColor(SK_ColorBLUE);
        *(bitmap.getAddr32(0, 0)) = SK_ColorGREEN;
        SkShader* shader = SkShader::CreateBitmapShader(bitmap, SkShader::kClamp_TileMode,
                                                        SkShader::kClamp_TileMode);
        paint.setShader(shader)->unref();
        REPORTER_ASSERT(reporter,
                        shader->asABitmap(NULL, NULL, NULL) == SkShader::kDefault_BitmapType);

        canvas->drawRect(SkRect::MakeWH(10, 10), paint);
    }
    picture.reset(recorder.endRecording());
    REPORTER_ASSERT(reporter, picture->willPlayBackBitmaps());
}

void PlatformContextSkiaJava::drawRect(SkRect rect)
{
    SkPaint paint;
    int fillcolorNotTransparent = m_state->m_fillColor & 0xFF000000;
    if (fillcolorNotTransparent) {
        setupPaintForFilling(&paint);
        canvas()->drawRect(rect, paint);
    }

    if (m_state->m_strokeStyle != WebCore::NoStroke &&
        (m_state->m_strokeColor & 0xFF000000)) {
        // We do a fill of four rects to simulate the stroke of a border.
        SkColor oldFillColor = m_state->m_fillColor;

        // setFillColor() will set the shader to NULL, so save a ref to it now. 
        SkShader* oldFillShader = m_state->m_fillShader;
        oldFillShader->safeRef();
        setFillColor(m_state->m_strokeColor);
        paint.reset();
        setupPaintForFilling(&paint);
        SkRect topBorder = { rect.fLeft, rect.fTop, rect.fRight, rect.fTop + 1 };
        canvas()->drawRect(topBorder, paint);
        SkRect bottomBorder = { rect.fLeft, rect.fBottom - 1, rect.fRight, rect.fBottom };
        canvas()->drawRect(bottomBorder, paint);
        SkRect leftBorder = { rect.fLeft, rect.fTop + 1, rect.fLeft + 1, rect.fBottom - 1 };
        canvas()->drawRect(leftBorder, paint);
        SkRect rightBorder = { rect.fRight - 1, rect.fTop + 1, rect.fRight, rect.fBottom - 1 };
        canvas()->drawRect(rightBorder, paint);
        setFillColor(oldFillColor);
        setFillShader(oldFillShader);
        oldFillShader->safeUnref();
    }
}

SkPDFShader::State::State(const SkShader& shader,
                          const SkMatrix& canvasTransform, const SkIRect& bbox)
        : fCanvasTransform(canvasTransform),
          fBBox(bbox),
          fPixelGeneration(0) {
    fInfo.fColorCount = 0;
    fInfo.fColors = NULL;
    fInfo.fColorOffsets = NULL;
    shader.getLocalMatrix(&fShaderTransform);
    fImageTileModes[0] = fImageTileModes[1] = SkShader::kClamp_TileMode;

    fType = shader.asAGradient(&fInfo);

    if (fType == SkShader::kNone_GradientType) {
        SkShader::BitmapType bitmapType;
        SkMatrix matrix;
        bitmapType = shader.asABitmap(&fImage, &matrix, fImageTileModes, NULL);
        if (bitmapType != SkShader::kDefault_BitmapType) {
            fImage.reset();
            return;
        }
        SkASSERT(matrix.isIdentity());
        fPixelGeneration = fImage.getGenerationID();
    } else {
        fColorData.set(sk_malloc_throw(
                    fInfo.fColorCount * (sizeof(SkColor) + sizeof(SkScalar))));
        fInfo.fColors = reinterpret_cast<SkColor*>(fColorData.get());
        fInfo.fColorOffsets =
            reinterpret_cast<SkScalar*>(fInfo.fColors + fInfo.fColorCount);
        shader.asAGradient(&fInfo);
    }
}

void
DrawTargetSkia::DrawSurface(SourceSurface *aSurface,
                            const Rect &aDest,
                            const Rect &aSource,
                            const DrawSurfaceOptions &aSurfOptions,
                            const DrawOptions &aOptions)
{
    if (aSurface->GetType() != SURFACE_SKIA) {
        return;
    }

    if (aSource.IsEmpty()) {
        return;
    }

    MarkChanged();

    SkRect destRect = RectToSkRect(aDest);
    SkRect sourceRect = RectToSkRect(aSource);

    SkMatrix matrix;
    matrix.setRectToRect(sourceRect, destRect, SkMatrix::kFill_ScaleToFit);

    const SkBitmap& bitmap = static_cast<SourceSurfaceSkia*>(aSurface)->GetBitmap();

    AutoPaintSetup paint(mCanvas.get(), aOptions);
    SkShader *shader = SkShader::CreateBitmapShader(bitmap, SkShader::kClamp_TileMode, SkShader::kClamp_TileMode);
    shader->setLocalMatrix(matrix);
    SkSafeUnref(paint.mPaint.setShader(shader));
    if (aSurfOptions.mFilter != FILTER_LINEAR) {
        paint.mPaint.setFilterBitmap(false);
    }
    mCanvas->drawRect(destRect, paint.mPaint);
}

    virtual void onDraw(SkCanvas* canvas) {

        SkPoint pts[2] = {
            { 0, 0 },
            { SkIntToScalar(100), SkIntToScalar(100) }
        };
        SkShader::TileMode tm = SkShader::kClamp_TileMode;
        SkRect r = { 0, 0, SkIntToScalar(100), SkIntToScalar(100) };
        SkPaint paint;
        paint.setAntiAlias(true);

        canvas->translate(SkIntToScalar(20), SkIntToScalar(20));
        for (size_t i = 0; i < SK_ARRAY_COUNT(gGradData); i++) {
            canvas->save();
            for (size_t j = 0; j < SK_ARRAY_COUNT(gGradMakers); j++) {
                SkShader* shader = gGradMakers[j](pts, gGradData[i], tm, NULL);

                // apply an increasing y perspective as we move to the right
                SkMatrix perspective;
                perspective.setIdentity();
                perspective.setPerspY(SkScalarDiv(SkIntToScalar((unsigned) i+1),
                                      SkIntToScalar(500)));
                perspective.setSkewX(SkScalarDiv(SkIntToScalar((unsigned) i+1),
                                     SkIntToScalar(10)));
                shader->setLocalMatrix(perspective);

                paint.setShader(shader);
                canvas->drawRect(r, paint);
                shader->unref();
                canvas->translate(0, SkIntToScalar(120));
            }
            canvas->restore();
            canvas->translate(SkIntToScalar(120), 0);
        }
    }

/*
 * When a function want to use the paint associated with a canvas to
 * draw, it should call _prepare_paint() can make the paint ready.
 * And, call _finish_paint() when the paint is no more used.
 */
static void
_prepare_paint(mbe_t *mbe, SkPaint::Style style) {
    SkPaint *paint = mbe->paint;
    mbe_pattern_t *ptn = mbe->states->ptn;
    SkShader *shader;
    co_aix matrix[6];
    SkMatrix skmatrix;

    paint->setStyle(style);

    if(ptn != NULL) {
	/* Local matrix of SkShader is a mapping from source pattern to
	 * user space.  Unlikely, for Cairo is a mapping from user space
	 * to source pattern.
	 */
	shader = ptn->shader;
	matrix_mul(mbe->states->matrix, ptn->matrix, matrix);
	MB_MATRIX_2_SKMATRIX(skmatrix, matrix);
	shader->setLocalMatrix(skmatrix);
	paint->setShader(shader);
    }

    if(style == SkPaint::kStroke_Style)
	paint->setStrokeWidth(CO_AIX_2_SKSCALAR(mbe->states->line_width));

    if(ptn != NULL && ptn->has_size)
	_prepare_sized_pattern(mbe, ptn);
}

	ShaderView()
    {
        SkImageDecoder::DecodeFile("/cover.png", &fBitmap);

        SkPoint pts[2];
        SkColor colors[2];
        
        pts[0].set(0, 0);
        pts[1].set(SkIntToScalar(100), 0);
        colors[0] = SK_ColorRED;
        colors[1] = SK_ColorBLUE;
        SkShader* shaderA = SkGradientShader::CreateLinear(pts, colors, NULL, 2, SkShader::kClamp_TileMode);
        
        pts[0].set(0, 0);
        pts[1].set(0, SkIntToScalar(100));
        colors[0] = SK_ColorBLACK;
        colors[1] = SkColorSetARGB(0x80, 0, 0, 0);
        SkShader* shaderB = SkGradientShader::CreateLinear(pts, colors, NULL, 2, SkShader::kClamp_TileMode);
        
        SkXfermode* mode = SkPorterDuff::CreateXfermode(SkPorterDuff::kDstIn_Mode);

        fShader = new SkComposeShader(shaderA, shaderB, mode);
        shaderA->unref();
        shaderB->unref();
        mode->unref();
    }

static cairo_status_t
_cairo_skia_context_set_source (void *abstract_cr,
				cairo_pattern_t *source)
{
    cairo_skia_context_t *cr = (cairo_skia_context_t *) abstract_cr;
    SkColor color;

    if (cr->source != NULL) {
	if (cr->source_image != NULL) {
	    _cairo_surface_release_source_image (cr->source, cr->source_image, cr->source_extra);
	    cr->source_image = NULL;
	}
	cairo_surface_destroy (cr->source);
	cr->source = NULL;
    }

    if (pattern_to_sk_color (source, color)) {
	cr->paint->setColor (color);
    } else {
	SkShader *shader = source_to_sk_shader (cr, source);
	if (shader == NULL) {
	    UNSUPPORTED;
	    return CAIRO_STATUS_SUCCESS;
	}

	cr->paint->setShader (shader);
	shader->unref ();

	cr->paint->setFilterBitmap (pattern_filter_to_sk (source));
    }

    /* XXX change notification */
    return CAIRO_STATUS_SUCCESS;
}

bool SkPaint2GrPaint(GrContext* context, GrRenderTarget* rt, const SkPaint& skPaint,
                     const SkMatrix& viewM, bool constantColor, GrPaint* grPaint) {
    SkShader* shader = skPaint.getShader();
    if (NULL == shader) {
        return SkPaint2GrPaintNoShader(context, rt, skPaint, SkColor2GrColor(skPaint.getColor()),
                                       constantColor, grPaint);
    }

    GrColor paintColor = SkColor2GrColor(skPaint.getColor());

    // Start a new block here in order to preserve our context state after calling
    // asFragmentProcessor(). Since these calls get passed back to the client, we don't really
    // want them messing around with the context.
    {
        // Allow the shader to modify paintColor and also create an effect to be installed as
        // the first color effect on the GrPaint.
        GrFragmentProcessor* fp = NULL;
        if (!shader->asFragmentProcessor(context, skPaint, viewM, NULL, &paintColor,
                                         grPaint->getProcessorDataManager(), &fp)) {
            return false;
        }
        if (fp) {
            grPaint->addColorProcessor(fp)->unref();
            constantColor = false;
        }
    }

    // The grcolor is automatically set when calling asFragmentProcessor.
    // If the shader can be seen as an effect it returns true and adds its effect to the grpaint.
    return SkPaint2GrPaintNoShader(context, rt, skPaint, paintColor, constantColor, grPaint);
}

static void drawmarshmallow(SkCanvas* canvas) {
    SkBitmap bitmap;
    SkPaint paint;
    SkRect r;
    SkMatrix m;

    SkImageDecoder::DecodeFile("/Users/reed/Downloads/3elfs.jpg", &bitmap);
    if (!bitmap.pixelRef()) {
        return;
    }

    SkShader* s = SkShader::CreateBitmapShader(bitmap,
                                               SkShader::kRepeat_TileMode,
                                               SkShader::kRepeat_TileMode);
    paint.setShader(s)->unref();
    m.setTranslate(SkIntToScalar(250), SkIntToScalar(134));
    s->setLocalMatrix(m);

    r.set(SkIntToScalar(250),
          SkIntToScalar(134),
          SkIntToScalar(250 + 449),
          SkIntToScalar(134 + 701));
    paint.setFlags(2);

    canvas->drawRect(r, paint);
}

GrFragmentProcessor* GrPerlinNoiseEffect::TestCreate(SkRandom* random,
                                                     GrContext* context,
                                                     const GrCaps&,
                                                     GrTexture**) {
    int      numOctaves = random->nextRangeU(2, 10);
    bool     stitchTiles = random->nextBool();
    SkScalar seed = SkIntToScalar(random->nextU());
    SkISize  tileSize = SkISize::Make(random->nextRangeU(4, 4096), random->nextRangeU(4, 4096));
    SkScalar baseFrequencyX = random->nextRangeScalar(0.01f,
                                                      0.99f);
    SkScalar baseFrequencyY = random->nextRangeScalar(0.01f,
                                                      0.99f);

    SkShader* shader = random->nextBool() ?
        SkPerlinNoiseShader::CreateFractalNoise(baseFrequencyX, baseFrequencyY, numOctaves, seed,
                                                stitchTiles ? &tileSize : NULL) :
        SkPerlinNoiseShader::CreateTurbulence(baseFrequencyX, baseFrequencyY, numOctaves, seed,
                                             stitchTiles ? &tileSize : NULL);

    SkPaint paint;
    GrColor paintColor;
    GrFragmentProcessor* effect;
    SkAssertResult(shader->asFragmentProcessor(context, paint,
                                               GrTest::TestMatrix(random), NULL,
                                               &paintColor, &effect));

    SkDELETE(shader);

    return effect;
}