alpha threshold bitmap shader
Committed: http://code.google.com/p/skia/source/detail?r=11122
R=reed@google.com
Author: bsalomon@google.com
Review URL: https://chromiumcodereview.appspot.com/23707019
git-svn-id: http://skia.googlecode.com/svn/trunk/include@11131 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/core/SkShader.h b/core/SkShader.h
index e1cab96..2632830 100644
--- a/core/SkShader.h
+++ b/core/SkShader.h
@@ -318,9 +318,11 @@
virtual GradientType asAGradient(GradientInfo* info) const;
/**
- * If the shader subclass has a GrEffect implementation, this installs an effect on the stage.
- * The GrContext may be used by the effect to create textures. The GPU device does not call
- * setContext. Instead we pass the paint here in case the shader needs paint info.
+ * If the shader subclass has a GrEffect implementation, this resturns the effect to install.
+ * The incoming color to the effect has r=g=b=a all extracted from the SkPaint's alpha.
+ * The output color should be the computed SkShader premul color modulated by the incoming
+ * color. The GrContext may be used by the effect to create textures. The GPU device does not
+ * call setContext. Instead we pass the SkPaint here in case the shader needs paint info.
*/
virtual GrEffectRef* asNewEffect(GrContext* context, const SkPaint& paint) const;
diff --git a/effects/SkBitmapAlphaThresholdShader.h b/effects/SkBitmapAlphaThresholdShader.h
new file mode 100644
index 0000000..61596da
--- /dev/null
+++ b/effects/SkBitmapAlphaThresholdShader.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkShader.h"
+#include "SkBitmap.h"
+#include "SkRegion.h"
+#include "SkString.h"
+
+class SK_API SkBitmapAlphaThresholdShader : public SkShader {
+public:
+ /**
+ * Creates a shader that samples a bitmap and a region. If the sample is inside the region
+ * the alpha of the bitmap color is boosted up to a threshold value. If it is
+ * outside the region then the bitmap alpha is decreased to the threshold value.
+ * The 0,0 point of the region corresponds to the upper left corner of the bitmap
+ * Currently, this only has a GPU implementation, doesn't respect the paint's bitmap
+ * filter setting, and always uses clamp mode.
+ */
+ static SkShader* Create(const SkBitmap& bitmap, const SkRegion& region, U8CPU threshold);
+};
diff --git a/gpu/GrEffect.h b/gpu/GrEffect.h
index 942e580..a84810c 100644
--- a/gpu/GrEffect.h
+++ b/gpu/GrEffect.h
@@ -204,8 +204,9 @@
protected:
/**
* Subclasses call this from their constructor to register GrTextureAccesses. The effect
- * subclass manages the lifetime of the accesses (this function only stores a pointer). This
- * must only be called from the constructor because GrEffects are immutable.
+ * subclass manages the lifetime of the accesses (this function only stores a pointer). The
+ * GrTextureAccess is typically a member field of the GrEffet subclass. This must only be
+ * called from the constructor because GrEffects are immutable.
*/
void addTextureAccess(const GrTextureAccess* textureAccess);
diff --git a/gpu/GrTextureAccess.h b/gpu/GrTextureAccess.h
index 0f44807..f8bb554 100644
--- a/gpu/GrTextureAccess.h
+++ b/gpu/GrTextureAccess.h
@@ -18,7 +18,7 @@
* Represents the filtering and tile modes used to access a texture. It is mostly used with
* GrTextureAccess (defined below). Also, some of the texture cache methods require knowledge about
* filtering and tiling to perform a cache lookup. If it wasn't for this latter usage this would
- * be folded into GrTextureAccess.
+ * be folded into GrTextureAccess. The default is clamp tile modes and no filtering.
*/
class GrTextureParams {
public:
