add readPixels to SkSurface (later try to remove it from SkCanvas)

BUG=skia:
TBR=bsalomon, robertphilips

Review URL: https://codereview.chromium.org/789993002

diff --git a/include/core/SkSurface.h b/include/core/SkSurface.h
index 0e238f8..62d2252 100644 (file)
--- a/include/core/SkSurface.h
+++ b/include/core/SkSurface.h
@@ -212,6 +212,35 @@ public:
      */
     const void* peekPixels(SkImageInfo* info, size_t* rowBytes);
 
+    /**
+     *  Copy the pixels from the surface into the specified buffer (pixels + rowBytes),
+     *  converting them into the requested format (dstInfo). The base-layer pixels are read
+     *  starting at the specified (srcX,srcY) location in the coordinate system of the base-layer.
+     *
+     *  The specified ImageInfo and (srcX,srcY) offset specifies a source rectangle
+     *
+     *      srcR.setXYWH(srcX, srcY, dstInfo.width(), dstInfo.height());
+     *
+     *  srcR is intersected with the bounds of the base-layer. If this intersection is not empty,
+     *  then we have two sets of pixels (of equal size). Replace the dst pixels with the
+     *  corresponding src pixels, performing any colortype/alphatype transformations needed
+     *  (in the case where the src and dst have different colortypes or alphatypes).
+     *
+     *  This call can fail, returning false, for several reasons:
+     *  - If srcR does not intersect the surface bounds.
+     *  - If the requested colortype/alphatype cannot be converted from the base-layer's types.
+     */
+    bool readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
+                    int srcX, int srcY);
+
+    /**
+     *  Helper for allocating pixels and then calling readPixels(info, ...). The bitmap is resized
+     *  to the intersection of srcRect and the surface bounds (if srcRect is non-null).
+     *  On success, pixels will be allocated in bitmap and true returned. On failure,
+     *  false is returned and bitmap will be set to empty.
+     */
+    bool readPixels(SkBitmap* dst, const SkIRect* srcRect = NULL);
+
     const SkSurfaceProps& props() const { return fProps; }
 
 protected:

diff --git a/src/image/SkSurface.cpp b/src/image/SkSurface.cpp
index 3ca5747..13b7d65 100644 (file)
--- a/src/image/SkSurface.cpp
+++ b/src/image/SkSurface.cpp
@@ -170,6 +170,20 @@ const void* SkSurface::peekPixels(SkImageInfo* info, size_t* rowBytes) {
     return this->getCanvas()->peekPixels(info, rowBytes);
 }
 
+bool SkSurface::readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
+                           int srcX, int srcY) {
+    return this->getCanvas()->readPixels(dstInfo, dstPixels, dstRowBytes, srcX, srcY);
+}
+
+bool SkSurface::readPixels(SkBitmap* dst, const SkIRect* srcRect) {
+    SkIRect storage;
+    if (NULL == srcRect) {
+        storage.set(0, 0, this->width(), this->height());
+        srcRect = &storage;
+    }
+    return this->getCanvas()->readPixels(*srcRect, dst);
+}
+
 //////////////////////////////////////////////////////////////////////////////////////
 #ifdef SK_SUPPORT_LEGACY_TEXTRENDERMODE