GrGradientShader Namespace Reference

Functions
static GrFPResult	apply_matrix (std::unique_ptr< GrFragmentProcessor > fp, const SkShaders::MatrixRec &rec, const SkMatrix &postInv)
std::unique_ptr< GrFragmentProcessor >	MakeGradientFP (const SkGradientBaseShader &shader, const GrFPArgs &args, const SkShaders::MatrixRec &mRec, std::unique_ptr< GrFragmentProcessor > layout, const SkMatrix *overrideMatrix)
std::unique_ptr< GrFragmentProcessor >	MakeLinear (const SkLinearGradient &shader, const GrFPArgs &args, const SkShaders::MatrixRec &mRec)

Function Documentation

apply_matrix()

static GrFPResult GrGradientShader::apply_matrix ( std::unique_ptr< GrFragmentProcessor >  fp, const SkShaders::MatrixRec &  rec, const SkMatrix &  postInv  )

static

Produces an FP that muls its input coords by the inverse of the pending matrix and then samples the passed FP with those coordinates. 'postInv' is an additional matrix to post-apply to the inverted pending matrix. If the pending matrix is not invertible the GrFPResult's bool will be false and the passed FP will be returned to the caller in the GrFPResult.

Definition at line 781 of file GrGradientShader.cpp.

                                                        {
    auto [total, ok] = rec.applyForFragmentProcessor(postInv);
    if (!ok) {
        return {false, std::move(fp)};
    }
    // GrMatrixEffect returns 'fp' if total worked out to identity.
    return {true, GrMatrixEffect::Make(total, std::move(fp))};
}

MakeGradientFP()

std::unique_ptr< GrFragmentProcessor > GrGradientShader::MakeGradientFP	(	const SkGradientBaseShader &	shader,
		const GrFPArgs &	args,
		const SkShaders::MatrixRec &	mRec,
		std::unique_ptr< GrFragmentProcessor >	layout,
		const SkMatrix *	overrideMatrix
	)

Definition at line 794 of file GrGradientShader.cpp.

                                                                                    {
    // No shader is possible if a layout couldn't be created, e.g. a layout-specific Make() returned
    // null.
    if (layout == nullptr) {
        return nullptr;
    }
 
    // Some two-point conical gradients use a custom matrix here. Otherwise, use
    // SkGradientBaseShader's matrix;
    if (!overrideMatrix) {
        overrideMatrix = &shader.getGradientMatrix();
    }
    bool success;
    std::tie(success, layout) = apply_matrix(std::move(layout), mRec, *overrideMatrix);
    if (!success) {
        return nullptr;
    }
 
    // Convert all colors into destination space and into SkPMColor4fs, and handle
    // premul issues depending on the interpolation mode.
    //
    // SkGradientShader stores positions implicitly when they are evenly spaced, but the getPos()
    // implementation performs a branch for every position index. Since the shader conversion
    // requires lots of position tests, instruct the xformer to calculate all of the positions up
    // front if needed.
    SkColor4fXformer xformedColors(
            &shader, args.fDstColorInfo->colorSpace(), /*forceExplicitPositions=*/true);
    const SkPMColor4f* colors = xformedColors.fColors.begin();
    const SkScalar* positions = xformedColors.fPositions;
    const int colorCount = xformedColors.fColors.size();
 
    bool allOpaque = true;
    for (int i = 0; i < colorCount; i++) {
        if (allOpaque && !SkScalarNearlyEqual(colors[i].fA, 1.0)) {
            allOpaque = false;
        }
    }
 
    // All gradients are colorized the same way, regardless of layout
    std::unique_ptr<GrFragmentProcessor> colorizer = make_uniform_colorizer(
            colors, positions, colorCount, shader.interpolateInPremul(), args);
 
    if (colorizer) {
        // If we made a uniform colorizer, wrap it in a conversion from interpolated space to
        // destination. This also applies any final premultiplication.
        colorizer = make_interpolated_to_dst(std::move(colorizer),
                                             shader.fInterpolation,
                                             xformedColors.fIntermediateColorSpace.get(),
                                             *args.fDstColorInfo,
                                             allOpaque);
    } else {
        // If we failed to make a uniform colorizer, we need to rasterize the gradient to a
        // texture (which can handle arbitrarily complex gradients). This method directly encodes
        // the result of the interpolated-to-dst into the texture, so we skip the wrapper FP above.
        //
        // Also, note that the texture technique has limited sampling resolution, and always blurs
        // hard-stops.)
        colorizer = make_textured_colorizer(colors,
                                            positions,
                                            colorCount,
                                            allOpaque,
                                            shader.fInterpolation,
                                            xformedColors.fIntermediateColorSpace.get(),
                                            args.fDstColorInfo->colorSpace(),
                                            args);
    }
 
    if (colorizer == nullptr) {
        return nullptr;
    }
 
    // If interpolation space is different than destination, wrap the colorizer in a conversion.
    // This also handles any final premultiplication, etc.
 
    // All tile modes are supported (unless something was added to SkShader)
    std::unique_ptr<GrFragmentProcessor> gradient;
    switch(shader.getTileMode()) {
        case SkTileMode::kRepeat:
            gradient = make_tiled_gradient(args, std::move(colorizer), std::move(layout),
                                           /* mirror */ false, allOpaque);
            break;
        case SkTileMode::kMirror:
            gradient = make_tiled_gradient(args, std::move(colorizer), std::move(layout),
                                           /* mirror */ true, allOpaque);
            break;
        case SkTileMode::kClamp: {
            // For the clamped mode, the border colors are the first and last colors, corresponding
            // to t=0 and t=1, because SkGradientBaseShader enforces that by adding color stops as
            // appropriate. If there is a hard stop, this grabs the expected outer colors for the
            // border.
 
            // However, we need to finish converting to destination color space. (These are still
            // in the interpolated color space).
            SkPMColor4f borderColors[2] = { colors[0], colors[colorCount - 1] };
            SkArenaAlloc alloc(/*firstHeapAllocation=*/0);
            SkRasterPipeline p(&alloc);
            SkRasterPipeline_MemoryCtx ctx = { borderColors, 0 };
 
            p.append(SkRasterPipelineOp::load_f32, &ctx);
            SkGradientBaseShader::AppendInterpolatedToDstStages(
                    &p,
                    &alloc,
                    allOpaque,
                    shader.fInterpolation,
                    xformedColors.fIntermediateColorSpace.get(),
                    args.fDstColorInfo->colorSpace());
            p.append(SkRasterPipelineOp::store_f32, &ctx);
            p.run(0, 0, 2, 1);
 
            gradient = make_clamped_gradient(std::move(colorizer), std::move(layout),
                                             borderColors[0], borderColors[1], allOpaque);
            break;
        }
        case SkTileMode::kDecal:
            // Even if the gradient colors are opaque, the decal borders are transparent so
            // disable that optimization
            gradient = make_clamped_gradient(std::move(colorizer), std::move(layout),
                                             SK_PMColor4fTRANSPARENT, SK_PMColor4fTRANSPARENT,
                                             /* colorsAreOpaque */ false);
            break;
    }
 
    return gradient;
}

MakeLinear()

std::unique_ptr< GrFragmentProcessor > GrGradientShader::MakeLinear	(	const SkLinearGradient &	shader,
		const GrFPArgs &	args,
		const SkShaders::MatrixRec &	mRec
	)

Definition at line 923 of file GrGradientShader.cpp.

                                                                                {
    // We add a tiny delta to t. When gradient stops are set up so that a hard stop in a vertically
    // or horizontally oriented gradient falls exactly at a column or row of pixel centers we can
    // get slightly different interpolated t values along the column/row. By adding the delta
    // we will consistently get the color to the "right" of the stop. Of course if the hard stop
    // falls at X.5 - delta then we still could get inconsistent results, but that is much less
    // likely. crbug.com/938592
    // If/when we add filtering of the gradient this can be removed.
    static const SkRuntimeEffect* effect = SkMakeRuntimeEffect(SkRuntimeEffect::MakeForShader,
        "half4 main(float2 coord) {"
            "return half4(half(coord.x) + 0.00001, 1, 0, 0);" // y = 1 for always valid
        "}"
    );
    // The linear gradient never rejects a pixel so it doesn't change opacity
    auto fp = GrSkSLFP::Make(effect, "LinearLayout", /*inputFP=*/nullptr,
                             GrSkSLFP::OptFlags::kPreservesOpaqueInput);
    return MakeGradientFP(shader, args, mRec, std::move(fp));
}