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Unified Diff: include/core/SkCanvas.h

Issue 161733002: add peekPixels to SkCanvas and SkSurface (Closed) Base URL: https://skia.googlecode.com/svn/trunk
Patch Set: Created 6 years, 10 months ago
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Index: include/core/SkCanvas.h
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index 7235efb2f0a9cd3b23132541d9c695b0c81e1704..971e4402d8fc0d20787877ba1f6976f6d07d59b0 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -76,6 +76,12 @@ public:
SkMetaData& getMetaData();
+ /**
+ * Return ImageInfo for this canvas. If the canvas is not backed by pixels
+ * (cpu or gpu), then the info's ColorType will be kUnknown_SkColorType.
+ */
+ SkImageInfo imageInfo() const;
+
///////////////////////////////////////////////////////////////////////////
/**
@@ -84,16 +90,19 @@ public:
void flush();
/**
+ * DEPRECATED: call imageInfo() instead.
* Return the width/height of the underlying device. The current drawable
* area may be small (due to clipping or saveLayer). For a canvas with
* no device, 0,0 will be returned.
*/
SkISize getDeviceSize() const;
- /** Return the canvas' device object, which may be null. The device holds
- the bitmap of the pixels that the canvas draws into. The reference count
- of the returned device is not changed by this call.
- */
+ /**
+ * DEPRECATED.
+ * Return the canvas' device object, which may be null. The device holds
+ * the bitmap of the pixels that the canvas draws into. The reference count
+ * of the returned device is not changed by this call.
+ */
SkBaseDevice* getDevice() const;
/**
@@ -126,6 +135,20 @@ public:
///////////////////////////////////////////////////////////////////////////
/**
+ * If the canvas has pixels (and is not recording to a picture or other
+ * non-raster target) and has direct access to its pixels (i.e. they are in
+ * local RAM) return the const-address of those pixels, and if not null,
+ * return the ImageInfo and rowBytes. The returned address is only valid
+ * while the canvas object is in scope and unchanged. Any API calls made on
+ * canvas (or its parent surface if any) will invalidate the
+ * returned address (and associated information).
+ *
+ * On failure, returns NULL and the info and rowBytes parameters are
+ * ignored.
+ */
+ const void* peekPixels(SkImageInfo* info, size_t* rowBytes);
+
+ /**
* This enum can be used with read/writePixels to perform a pixel ops to or
* from an 8888 config other than Skia's native config (SkPMColor). There
* are three byte orders supported: native, BGRA, and RGBA. Each has a
@@ -1019,6 +1042,9 @@ protected:
// default impl defers to getDevice()->newSurface(info)
virtual SkSurface* onNewSurface(const SkImageInfo&);
+ // default impl defers to its device
+ virtual const void* onPeekPixels(SkImageInfo*, size_t* rowBytes);
+
// Returns the canvas to be used by DrawIter. Default implementation
// returns this. Subclasses that encapsulate an indirect canvas may
// need to overload this method. The impl must keep track of this, as it
@@ -1206,4 +1232,47 @@ private:
};
#define SkAutoCommentBlock(...) SK_REQUIRE_LOCAL_VAR(SkAutoCommentBlock)
+/**
+ * If the caller wants read-only access to the pixels in a canvas, it can just
+ * call canvas->peekPixels(), since that is the fastest way to "peek" at the
+ * pixels on a raster-backed canvas.
+ *
+ * If the canvas has pixels, but they are not readily available to the CPU
+ * (e.g. gpu-backed), then peekPixels() will fail, but readPixels() will
+ * succeed (though be slower, since it will return a copy of the pixels).
+ *
+ * SkAutoROCanvasPixels encapsulates these two techniques, trying first to call
+ * peekPixels() (for performance), but if that fails, calling readPixels() and
+ * storing the copy locally.
+ *
+ * The caller must respect the restrictions associated with peekPixels(), since
+ * that may have been called: The returned information is invalidated if...
+ * - any API is called on the canvas (or its parent surface if present)
+ * - the canvas goes out of scope
+ */
+class SkAutoROCanvasPixels : SkNoncopyable {
+public:
+ SkAutoROCanvasPixels(SkCanvas* canvas);
+
+ // returns NULL on failure
+ const void* addr() const { return fAddr; }
+
+ // undefined if addr() == NULL
+ size_t rowBytes() const { return fRowBytes; }
+
+ // undefined if addr() == NULL
+ const SkImageInfo& info() const { return fInfo; }
+
+ // helper that, if returns true, installs the pixels into the bitmap. Note
+ // that the bitmap may reference the address returned by peekPixels(), so
+ // the caller must respect the restrictions associated with peekPixels().
+ bool asROBitmap(SkBitmap*) const;
+
+private:
+ SkBitmap fBitmap; // used if peekPixels() fails
+ const void* fAddr; // NULL on failure
+ SkImageInfo fInfo;
+ size_t fRowBytes;
+};
+
#endif
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