add shadermaskfilter

next steps:
- gpu impl (will look a lot like shader's asFragProcessor
- special-case rect-input (?)
- explore stages w/ mtklein

Bug: skia:7500
Change-Id: I71089e421d32443a3ddded6967b3e5bc67ed43f2
Reviewed-on: https://skia-review.googlesource.com/95104
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>

1 files changed, 117 insertions, 0 deletions

diff --git a/src/effects/SkShaderMaskFilter.cpp b/src/effects/SkShaderMaskFilter.cpp
new file mode 100644
index 0000000000..8693751899
--- /dev/null
+++ b/src/effects/SkShaderMaskFilter.cpp
@@ -0,0 +1,117 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCanvas.h"
+#include "SkReadBuffer.h"
+#include "SkShaderMaskFilter.h"
+#include "SkShader.h"
+#include "SkString.h"
+
+class SkShaderMF : public SkMaskFilter {
+public:
+    SkShaderMF(sk_sp<SkShader> shader) : fShader(std::move(shader)) {}
+
+    SkMask::Format getFormat() const override { return SkMask::kA8_Format; }
+
+    bool filterMask(SkMask* dst, const SkMask& src, const SkMatrix&,
+                    SkIPoint* margin) const override;
+
+    void computeFastBounds(const SkRect& src, SkRect* dst) const override {
+        *dst = src;
+    }
+
+    bool asABlur(BlurRec*) const override { return false; }
+
+    SK_TO_STRING_OVERRIDE()
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkShaderMF)
+
+private:
+    sk_sp<SkShader> fShader;
+
+    SkShaderMF(SkReadBuffer&);
+    void flatten(SkWriteBuffer&) const override;
+
+    friend class SkShaderMaskFilter;
+
+    typedef SkMaskFilter INHERITED;
+};
+
+#ifndef SK_IGNORE_TO_STRING
+void SkShaderMF::toString(SkString* str) const {
+    str->set("SkShaderMF:");
+}
+#endif
+
+sk_sp<SkFlattenable> SkShaderMF::CreateProc(SkReadBuffer& buffer) {
+    return SkShaderMaskFilter::Make(buffer.readShader());
+}
+
+void SkShaderMF::flatten(SkWriteBuffer& buffer) const {
+    buffer.writeFlattenable(fShader.get());
+}
+
+static void rect_memcpy(void* dst, size_t dstRB, const void* src, size_t srcRB,
+                        size_t copyBytes, int rows) {
+    for (int i = 0; i < rows; ++i) {
+        memcpy(dst, src, copyBytes);
+        dst = (char*)dst + dstRB;
+        src = (const char*)src + srcRB;
+    }
+}
+
+bool SkShaderMF::filterMask(SkMask* dst, const SkMask& src, const SkMatrix& ctm,
+                            SkIPoint* margin) const {
+    SkASSERT(src.fFormat == SkMask::kA8_Format);
+
+    if (margin) {
+        margin->set(0, 0);
+    }
+    dst->fBounds   = src.fBounds;
+    dst->fRowBytes = src.fBounds.width();   // need alignment?
+    dst->fFormat   = SkMask::kA8_Format;
+
+    if (src.fImage == nullptr) {
+        dst->fImage = nullptr;
+        return true;
+    }
+    size_t size = dst->computeImageSize();
+    if (0 == size) {
+        return false;   // too big to allocate, abort
+    }
+
+    // Allocate and initialize dst image with a copy of the src image
+    dst->fImage = SkMask::AllocImage(size);
+    rect_memcpy(dst->fImage, dst->fRowBytes, src.fImage, src.fRowBytes,
+                src.fBounds.width() * sizeof(uint8_t), src.fBounds.height());
+
+    // Now we have a dst-mask, just need to setup a canvas and draw into it
+    SkBitmap bitmap;
+    if (!bitmap.installMaskPixels(*dst)) {
+        return false;
+    }
+
+    SkPaint paint;
+    paint.setShader(fShader);
+    // this blendmode is the trick: we only draw the shader where the mask is
+    paint.setBlendMode(SkBlendMode::kSrcIn);
+
+    SkCanvas canvas(bitmap);
+    canvas.translate(-SkIntToScalar(dst->fBounds.fLeft), -SkIntToScalar(dst->fBounds.fTop));
+    canvas.concat(ctm);
+    canvas.drawPaint(paint);
+    return true;
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkMaskFilter> SkShaderMaskFilter::Make(sk_sp<SkShader> shader) {
+    return shader ? sk_sp<SkMaskFilter>(new SkShaderMF(std::move(shader))) : nullptr;
+}
+
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkShaderMaskFilter)
+    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkShaderMF)
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END