Merge from Chromium at DEPS revision 37.0.2062.117android-wear-5.0.0_r1android-l-preview_r2android-cts-5.0_r9android-cts-5.0_r8android-cts-5.0_r7android-cts-5.0_r6android-cts-5.0_r5android-cts-5.0_r4android-cts-5.0_r3android-5.0.2_r3android-5.0.2_r1android-5.0.1_r1android-5.0.0_r7android-5.0.0_r6android-5.0.0_r5.1android-5.0.0_r5android-5.0.0_r4android-5.0.0_r3android-5.0.0_r2android-5.0.0_r1lollipop-wear-releaselollipop-releaselollipop-devlollipop-cts-releasel-preview

This commit was generated by merge_to_master.py.

Change-Id: I9cd955d97932b42739ee7e6abb42e1f05d514410

7 files changed, 346 insertions, 141 deletions

diff --git a/include/core/SkBitmap.h b/include/core/SkBitmap.h
index d3c33a8e0..13e9aa372 100644
--- a/include/core/SkBitmap.h
+++ b/include/core/SkBitmap.h
@@ -643,6 +643,28 @@ public:
     }
 
     /**
+     *  Copy the bitmap's pixels into the specified buffer (pixels + rowBytes),
+     *  converting them into the requested format (SkImageInfo). The src pixels are read
+     *  starting at the specified (srcX,srcY) offset, relative to the top-left corner.
+     *
+     *  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 bitmap. 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 bitmap bounds.
+     *  - If the requested colortype/alphatype cannot be converted from the src's types.
+     *  - If the src pixels are not available.
+     */
+    bool readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
+                    int srcX, int srcY) const;
+
+    /**
      *  Returns true if this bitmap's pixels can be converted into the requested
      *  colorType, such that copyTo() could succeed.
      */
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index a08e82800..31429f941 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -230,30 +230,31 @@ public:
     /**
      *  Copy the pixels from the base-layer into the specified buffer (pixels + rowBytes),
      *  converting them into the requested format (SkImageInfo). The base-layer pixels are read
-     *  starting at the specified (x,y) location in the coordinate system of the base-layer.
+     *  starting at the specified (srcX,srcY) location in the coordinate system of the base-layer.
      *
-     *  The specified ImageInfo and (x,y) offset specifies a source rectangle
+     *  The specified ImageInfo and (srcX,srcY) offset specifies a source rectangle
      *
-     *      srcR(x, y, info.width(), info.height());
+     *      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), the "src" specified by base-layer at (x,y)
-     *  and the "dst" by info+pixels+rowBytes. 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).
+     *  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 base-layer bounds.
      *  - If the requested colortype/alphatype cannot be converted from the base-layer's types.
      *  - If this canvas is not backed by pixels (e.g. picture or PDF)
      */
-    bool readPixels(const SkImageInfo&, void* pixels, size_t rowBytes, int x, int y);
+    bool readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
+                    int srcX, int srcY);
 
     /**
      *  Helper for calling readPixels(info, ...). This call will check if bitmap has been allocated.
      *  If not, it will attempt to call allocPixels(). If this fails, it will return false. If not,
      *  it calls through to readPixels(info, ...) and returns its result.
      */
-    bool readPixels(SkBitmap* bitmap, int x, int y);
+    bool readPixels(SkBitmap* bitmap, int srcX, int srcY);
 
     /**
      *  Helper for allocating pixels and then calling readPixels(info, ...). The bitmap is resized
diff --git a/src/core/SkBitmap.cpp b/src/core/SkBitmap.cpp
index 789bf11b4..42254b518 100644
--- a/src/core/SkBitmap.cpp
+++ b/src/core/SkBitmap.cpp
@@ -873,11 +873,13 @@ bool SkBitmap::extractSubset(SkBitmap* result, const SkIRect& subset) const {
 #include "SkPaint.h"
 
 bool SkBitmap::canCopyTo(SkColorType dstColorType) const {
-    if (this->colorType() == kUnknown_SkColorType) {
+    const SkColorType srcCT = this->colorType();
+
+    if (srcCT == kUnknown_SkColorType) {
         return false;
     }
 
-    bool sameConfigs = (this->colorType() == dstColorType);
+    bool sameConfigs = (srcCT == dstColorType);
     switch (dstColorType) {
         case kAlpha_8_SkColorType:
         case kRGB_565_SkColorType:
@@ -890,15 +892,66 @@ bool SkBitmap::canCopyTo(SkColorType dstColorType) const {
             }
             break;
         case kARGB_4444_SkColorType:
-            return sameConfigs || kN32_SkColorType == this->colorType();
+            return sameConfigs || kN32_SkColorType == srcCT || kIndex_8_SkColorType == srcCT;
         default:
             return false;
     }
     return true;
 }
 
-bool SkBitmap::copyTo(SkBitmap* dst, SkColorType dstColorType,
-                      Allocator* alloc) const {
+#include "SkConfig8888.h"
+
+bool SkBitmap::readPixels(const SkImageInfo& requestedDstInfo, void* dstPixels, size_t dstRB,
+                          int x, int y) const {
+    if (kUnknown_SkColorType == requestedDstInfo.colorType()) {
+        return false;
+    }
+    if (NULL == dstPixels || dstRB < requestedDstInfo.minRowBytes()) {
+        return false;
+    }
+    if (0 == requestedDstInfo.width() || 0 == requestedDstInfo.height()) {
+        return false;
+    }
+    
+    SkIRect srcR = SkIRect::MakeXYWH(x, y, requestedDstInfo.width(), requestedDstInfo.height());
+    if (!srcR.intersect(0, 0, this->width(), this->height())) {
+        return false;
+    }
+    
+    SkImageInfo dstInfo = requestedDstInfo;
+    // the intersect may have shrunk info's logical size
+    dstInfo.fWidth = srcR.width();
+    dstInfo.fHeight = srcR.height();
+    
+    // if x or y are negative, then we have to adjust pixels
+    if (x > 0) {
+        x = 0;
+    }
+    if (y > 0) {
+        y = 0;
+    }
+    // here x,y are either 0 or negative
+    dstPixels = ((char*)dstPixels - y * dstRB - x * dstInfo.bytesPerPixel());
+
+    //////////////
+    
+    SkAutoLockPixels alp(*this);
+    
+    // since we don't stop creating un-pixeled devices yet, check for no pixels here
+    if (NULL == this->getPixels()) {
+        return false;
+    }
+    
+    SkImageInfo srcInfo = this->info();
+    srcInfo.fWidth = dstInfo.width();
+    srcInfo.fHeight = dstInfo.height();
+    
+    const void* srcPixels = this->getAddr(srcR.x(), srcR.y());
+    return SkPixelInfo::CopyPixels(dstInfo, dstPixels, dstRB, srcInfo, srcPixels, this->rowBytes(),
+                                   this->getColorTable());
+}
+
+bool SkBitmap::copyTo(SkBitmap* dst, SkColorType dstColorType, Allocator* alloc) const {
     if (!this->canCopyTo(dstColorType)) {
         return false;
     }
@@ -971,59 +1024,21 @@ bool SkBitmap::copyTo(SkBitmap* dst, SkColorType dstColorType,
     // returned false.
     SkASSERT(tmpDst.pixelRef() != NULL);
 
-    /* do memcpy for the same configs cases, else use drawing
-    */
-    if (src->colorType() == dstColorType) {
-        if (tmpDst.getSize() == src->getSize()) {
-            memcpy(tmpDst.getPixels(), src->getPixels(), src->getSafeSize());
+    if (!src->readPixels(tmpDst.info(), tmpDst.getPixels(), tmpDst.rowBytes(), 0, 0)) {
+        return false;
+    }
 
-            SkPixelRef* dstPixelRef = tmpDst.pixelRef();
-            if (dstPixelRef->info() == fPixelRef->info()) {
-                dstPixelRef->cloneGenID(*fPixelRef);
-            }
-        } else {
-            const char* srcP = reinterpret_cast<const char*>(src->getPixels());
-            char* dstP = reinterpret_cast<char*>(tmpDst.getPixels());
-            // to be sure we don't read too much, only copy our logical pixels
-            size_t bytesToCopy = tmpDst.width() * tmpDst.bytesPerPixel();
-            for (int y = 0; y < tmpDst.height(); y++) {
-                memcpy(dstP, srcP, bytesToCopy);
-                srcP += src->rowBytes();
-                dstP += tmpDst.rowBytes();
-            }
-        }
-    } else if (kARGB_4444_SkColorType == dstColorType
-               && kN32_SkColorType == src->colorType()) {
-        if (src->alphaType() == kUnpremul_SkAlphaType) {
-            // Our method for converting to 4444 assumes premultiplied.
-            return false;
+    //  (for BitmapHeap) Clone the pixelref genID even though we have a new pixelref.
+    //  The old copyTo impl did this, so we continue it for now.
+    //
+    //  TODO: should we ignore rowbytes (i.e. getSize)? Then it could just be
+    //      if (src_pixelref->info == dst_pixelref->info)
+    //
+    if (src->colorType() == dstColorType && tmpDst.getSize() == src->getSize()) {
+        SkPixelRef* dstPixelRef = tmpDst.pixelRef();
+        if (dstPixelRef->info() == fPixelRef->info()) {
+            dstPixelRef->cloneGenID(*fPixelRef);
         }
-        SkASSERT(src->height() == tmpDst.height());
-        SkASSERT(src->width() == tmpDst.width());
-        for (int y = 0; y < src->height(); ++y) {
-            SkPMColor16* SK_RESTRICT dstRow = (SkPMColor16*) tmpDst.getAddr16(0, y);
-            SkPMColor* SK_RESTRICT srcRow = (SkPMColor*) src->getAddr32(0, y);
-            DITHER_4444_SCAN(y);
-            for (int x = 0; x < src->width(); ++x) {
-                dstRow[x] = SkDitherARGB32To4444(srcRow[x],
-                                                 DITHER_VALUE(x));
-            }
-        }
-    } else {
-        if (tmpDst.alphaType() == kUnpremul_SkAlphaType) {
-            // We do not support drawing to unpremultiplied bitmaps.
-            return false;
-        }
-
-        // Always clear the dest in case one of the blitters accesses it
-        // TODO: switch the allocation of tmpDst to call sk_calloc_throw
-        tmpDst.eraseColor(SK_ColorTRANSPARENT);
-
-        SkCanvas canvas(tmpDst);
-        SkPaint  paint;
-
-        paint.setDither(true);
-        canvas.drawBitmap(*src, 0, 0, &paint);
     }
 
     dst->swap(tmpDst);
diff --git a/src/core/SkBitmapDevice.cpp b/src/core/SkBitmapDevice.cpp
index 0f3cc2be5..1dfc3a6c0 100644
--- a/src/core/SkBitmapDevice.cpp
+++ b/src/core/SkBitmapDevice.cpp
@@ -155,59 +155,8 @@ void* SkBitmapDevice::onAccessPixels(SkImageInfo* info, size_t* rowBytes) {
     return NULL;
 }
 
-static void rect_memcpy(void* dst, size_t dstRB, const void* src, size_t srcRB, size_t bytesPerRow,
-                        int rowCount) {
-    SkASSERT(bytesPerRow <= srcRB);
-    SkASSERT(bytesPerRow <= dstRB);
-    for (int i = 0; i < rowCount; ++i) {
-        memcpy(dst, src, bytesPerRow);
-        dst = (char*)dst + dstRB;
-        src = (const char*)src + srcRB;
-    }
-}
-
 #include "SkConfig8888.h"
 
-static bool copy_pixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
-                        const SkImageInfo& srcInfo, const void* srcPixels, size_t srcRowBytes) {
-    if (srcInfo.dimensions() != dstInfo.dimensions()) {
-        return false;
-    }
-    if (4 == srcInfo.bytesPerPixel() && 4 == dstInfo.bytesPerPixel()) {
-        SkDstPixelInfo dstPI;
-        dstPI.fColorType = dstInfo.colorType();
-        dstPI.fAlphaType = dstInfo.alphaType();
-        dstPI.fPixels = dstPixels;
-        dstPI.fRowBytes = dstRowBytes;
-
-        SkSrcPixelInfo srcPI;
-        srcPI.fColorType = srcInfo.colorType();
-        srcPI.fAlphaType = srcInfo.alphaType();
-        srcPI.fPixels = srcPixels;
-        srcPI.fRowBytes = srcRowBytes;
-
-        return srcPI.convertPixelsTo(&dstPI, srcInfo.width(), srcInfo.height());
-    }
-    if (srcInfo.colorType() == dstInfo.colorType()) {
-        switch (srcInfo.colorType()) {
-            case kRGB_565_SkColorType:
-            case kAlpha_8_SkColorType:
-                break;
-            case kARGB_4444_SkColorType:
-                if (srcInfo.alphaType() != dstInfo.alphaType()) {
-                    return false;
-                }
-                break;
-            default:
-                return false;
-        }
-        rect_memcpy(dstPixels, dstRowBytes, srcPixels, srcRowBytes,
-                    srcInfo.width() * srcInfo.bytesPerPixel(), srcInfo.height());
-    }
-    // TODO: add support for more conversions as needed
-    return false;
-}
-
 bool SkBitmapDevice::onWritePixels(const SkImageInfo& srcInfo, const void* srcPixels,
                                    size_t srcRowBytes, int x, int y) {
     // since we don't stop creating un-pixeled devices yet, check for no pixels here
@@ -222,7 +171,7 @@ bool SkBitmapDevice::onWritePixels(const SkImageInfo& srcInfo, const void* srcPi
     void* dstPixels = fBitmap.getAddr(x, y);
     size_t dstRowBytes = fBitmap.rowBytes();
 
-    if (copy_pixels(dstInfo, dstPixels, dstRowBytes, srcInfo, srcPixels, srcRowBytes)) {
+    if (SkPixelInfo::CopyPixels(dstInfo, dstPixels, dstRowBytes, srcInfo, srcPixels, srcRowBytes)) {
         fBitmap.notifyPixelsChanged();
         return true;
     }
@@ -231,28 +180,7 @@ bool SkBitmapDevice::onWritePixels(const SkImageInfo& srcInfo, const void* srcPi
 
 bool SkBitmapDevice::onReadPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
                                   int x, int y) {
-    // since we don't stop creating un-pixeled devices yet, check for no pixels here
-    if (NULL == fBitmap.getPixels()) {
-        return false;
-    }
-
-    SkImageInfo srcInfo = fBitmap.info();
-
-    // perhaps can relax these in the future
-    if (4 != dstInfo.bytesPerPixel()) {
-        return false;
-    }
-    if (4 != srcInfo.bytesPerPixel()) {
-        return false;
-    }
-
-    srcInfo.fWidth = dstInfo.width();
-    srcInfo.fHeight = dstInfo.height();
-
-    const void* srcPixels = fBitmap.getAddr(x, y);
-    const size_t srcRowBytes = fBitmap.rowBytes();
-
-    return copy_pixels(dstInfo, dstPixels, dstRowBytes, srcInfo, srcPixels, srcRowBytes);
+    return fBitmap.readPixels(dstInfo, dstPixels, dstRowBytes, x, y);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/src/core/SkConfig8888.cpp b/src/core/SkConfig8888.cpp
index 189309dae..b0572c054 100644
--- a/src/core/SkConfig8888.cpp
+++ b/src/core/SkConfig8888.cpp
@@ -1,5 +1,15 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkBitmap.h"
+#include "SkCanvas.h"
 #include "SkConfig8888.h"
 #include "SkColorPriv.h"
+#include "SkDither.h"
 #include "SkMathPriv.h"
 #include "SkUnPreMultiply.h"
 
@@ -115,3 +125,135 @@ bool SkSrcPixelInfo::convertPixelsTo(SkDstPixelInfo* dst, int width, int height)
     }
     return true;
 }
+
+static void rect_memcpy(void* dst, size_t dstRB, const void* src, size_t srcRB, size_t bytesPerRow,
+                        int rowCount) {
+    SkASSERT(bytesPerRow <= srcRB);
+    SkASSERT(bytesPerRow <= dstRB);
+    for (int i = 0; i < rowCount; ++i) {
+        memcpy(dst, src, bytesPerRow);
+        dst = (char*)dst + dstRB;
+        src = (const char*)src + srcRB;
+    }
+}
+
+bool SkPixelInfo::CopyPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRB,
+                             const SkImageInfo& srcInfo, const void* srcPixels, size_t srcRB,
+                             SkColorTable* ctable) {
+    if (srcInfo.dimensions() != dstInfo.dimensions()) {
+        return false;
+    }
+
+    const int width = srcInfo.width();
+    const int height = srcInfo.height();
+
+    // Handle fancy alpha swizzling if both are ARGB32
+    if (4 == srcInfo.bytesPerPixel() && 4 == dstInfo.bytesPerPixel()) {
+        SkDstPixelInfo dstPI;
+        dstPI.fColorType = dstInfo.colorType();
+        dstPI.fAlphaType = dstInfo.alphaType();
+        dstPI.fPixels = dstPixels;
+        dstPI.fRowBytes = dstRB;
+        
+        SkSrcPixelInfo srcPI;
+        srcPI.fColorType = srcInfo.colorType();
+        srcPI.fAlphaType = srcInfo.alphaType();
+        srcPI.fPixels = srcPixels;
+        srcPI.fRowBytes = srcRB;
+        
+        return srcPI.convertPixelsTo(&dstPI, width, height);
+    }
+
+    // If they agree on colorType and the alphaTypes are compatible, then we just memcpy.
+    // Note: we've already taken care of 32bit colortypes above.
+    if (srcInfo.colorType() == dstInfo.colorType()) {
+        switch (srcInfo.colorType()) {
+            case kRGB_565_SkColorType:
+            case kAlpha_8_SkColorType:
+                break;
+            case kIndex_8_SkColorType:
+            case kARGB_4444_SkColorType:
+                if (srcInfo.alphaType() != dstInfo.alphaType()) {
+                    return false;
+                }
+                break;
+            default:
+                return false;
+        }
+        rect_memcpy(dstPixels, dstRB, srcPixels, srcRB, width * srcInfo.bytesPerPixel(), height);
+        return true;
+    }
+
+    /*
+     *  Begin section where we try to change colorTypes along the way. Not all combinations
+     *  are supported.
+     */
+
+    // Can no longer draw directly into 4444, but we can manually whack it for a few combinations
+    if (kARGB_4444_SkColorType == dstInfo.colorType() &&
+        (kN32_SkColorType == srcInfo.colorType() || kIndex_8_SkColorType == srcInfo.colorType())) {
+        if (srcInfo.alphaType() == kUnpremul_SkAlphaType) {
+            // Our method for converting to 4444 assumes premultiplied.
+            return false;
+        }
+        
+        const SkPMColor* table = NULL;
+        if (kIndex_8_SkColorType == srcInfo.colorType()) {
+            if (NULL == ctable) {
+                return false;
+            }
+            table = ctable->lockColors();
+        }
+
+        for (int y = 0; y < height; ++y) {
+            DITHER_4444_SCAN(y);
+            SkPMColor16* SK_RESTRICT dstRow = (SkPMColor16*)dstPixels;
+            if (table) {
+                const uint8_t* SK_RESTRICT srcRow = (const uint8_t*)srcPixels;
+                for (int x = 0; x < width; ++x) {
+                    dstRow[x] = SkDitherARGB32To4444(table[srcRow[x]], DITHER_VALUE(x));
+                }
+            } else {
+                const SkPMColor* SK_RESTRICT srcRow = (const SkPMColor*)srcPixels;
+                for (int x = 0; x < width; ++x) {
+                    dstRow[x] = SkDitherARGB32To4444(srcRow[x], DITHER_VALUE(x));
+                }
+            }
+            dstPixels = (char*)dstPixels + dstRB;
+            srcPixels = (const char*)srcPixels + srcRB;
+        }
+        
+        if (table) {
+            ctable->unlockColors();
+        }
+        return true;
+    }
+
+    if (dstInfo.alphaType() == kUnpremul_SkAlphaType) {
+        // We do not support drawing to unpremultiplied bitmaps.
+        return false;
+    }
+
+    // Final fall-back, draw with a canvas
+    //
+    // Always clear the dest in case one of the blitters accesses it
+    // TODO: switch the allocation of tmpDst to call sk_calloc_throw
+    {
+        SkBitmap bm;
+        if (!bm.installPixels(srcInfo, const_cast<void*>(srcPixels), srcRB, ctable, NULL, NULL)) {
+            return false;
+        }
+        SkAutoTUnref<SkCanvas> canvas(SkCanvas::NewRasterDirect(dstInfo, dstPixels, dstRB));
+        if (NULL == canvas.get()) {
+            return false;
+        }
+
+        SkPaint  paint;
+        paint.setDither(true);
+
+        canvas->clear(0);
+        canvas->drawBitmap(bm, 0, 0, &paint);
+        return true;
+    }
+}
+
diff --git a/src/core/SkConfig8888.h b/src/core/SkConfig8888.h
index 97a3433ad..da0cbc668 100644
--- a/src/core/SkConfig8888.h
+++ b/src/core/SkConfig8888.h
@@ -14,6 +14,10 @@ struct SkPixelInfo {
     SkColorType fColorType;
     SkAlphaType fAlphaType;
     size_t      fRowBytes;
+
+    static bool CopyPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
+                           const SkImageInfo& srcInfo, const void* srcPixels, size_t srcRowBytes,
+                           SkColorTable* srcCTable = NULL);
 };
 
 struct SkDstPixelInfo : SkPixelInfo {
diff --git a/tests/BitmapCopyTest.cpp b/tests/BitmapCopyTest.cpp
index 40cfbe0d5..4a49a6b48 100644
--- a/tests/BitmapCopyTest.cpp
+++ b/tests/BitmapCopyTest.cpp
@@ -185,7 +185,7 @@ static void writeCoordPixels(SkBitmap& bm, const Coordinates& coords) {
 static const Pair gPairs[] = {
     { kUnknown_SkColorType,     "000000"  },
     { kAlpha_8_SkColorType,     "010101"  },
-    { kIndex_8_SkColorType,     "011101"  },
+    { kIndex_8_SkColorType,     "011111"  },
     { kRGB_565_SkColorType,     "010101"  },
     { kARGB_4444_SkColorType,   "010111"  },
     { kN32_SkColorType,         "010111"  },
@@ -542,3 +542,96 @@ DEF_TEST(BitmapCopy, reporter) {
         } // for (size_t copyCase ...
     }
 }
+
+#include "SkColorPriv.h"
+#include "SkUtils.h"
+
+/**
+ *  Construct 4x4 pixels where we can look at a color and determine where it should be in the grid.
+ *  alpha = 0xFF, blue = 0x80, red = x, green = y
+ */
+static void fill_4x4_pixels(SkPMColor colors[16]) {
+    for (int y = 0; y < 4; ++y) {
+        for (int x = 0; x < 4; ++x) {
+            colors[y*4+x] = SkPackARGB32(0xFF, x, y, 0x80);
+        }
+    }
+}
+
+static bool check_4x4_pixel(SkPMColor color, unsigned x, unsigned y) {
+    SkASSERT(x < 4 && y < 4);
+    return  0xFF == SkGetPackedA32(color) &&
+            x    == SkGetPackedR32(color) &&
+            y    == SkGetPackedG32(color) &&
+            0x80 == SkGetPackedB32(color);
+}
+
+/**
+ *  Fill with all zeros, which will never match any value from fill_4x4_pixels
+ */
+static void clear_4x4_pixels(SkPMColor colors[16]) {
+    sk_memset32(colors, 0, 16);
+}
+
+// Much of readPixels is exercised by copyTo testing, since readPixels is the backend for that
+// method. Here we explicitly test subset copies.
+//
+DEF_TEST(BitmapReadPixels, reporter) {
+    const int W = 4;
+    const int H = 4;
+    const size_t rowBytes = W * sizeof(SkPMColor);
+    const SkImageInfo srcInfo = SkImageInfo::MakeN32Premul(W, H);
+    SkPMColor srcPixels[16];
+    fill_4x4_pixels(srcPixels);
+    SkBitmap srcBM;
+    srcBM.installPixels(srcInfo, srcPixels, rowBytes);
+
+    SkImageInfo dstInfo = SkImageInfo::MakeN32Premul(W, H);
+    SkPMColor dstPixels[16];
+
+    const struct {
+        bool     fExpectedSuccess;
+        SkIPoint fRequestedSrcLoc;
+        SkISize  fRequestedDstSize;
+        // If fExpectedSuccess, check these, otherwise ignore
+        SkIPoint fExpectedDstLoc;
+        SkIRect  fExpectedSrcR;
+    } gRec[] = {
+        { true,  { 0, 0 }, { 4, 4 }, { 0, 0 }, { 0, 0, 4, 4 } },
+        { true,  { 1, 1 }, { 2, 2 }, { 0, 0 }, { 1, 1, 3, 3 } },
+        { true,  { 2, 2 }, { 4, 4 }, { 0, 0 }, { 2, 2, 4, 4 } },
+        { true,  {-1,-1 }, { 2, 2 }, { 1, 1 }, { 0, 0, 1, 1 } },
+        { false, {-1,-1 }, { 1, 1 }, { 0, 0 }, { 0, 0, 0, 0 } },
+    };
+
+    for (size_t i = 0; i < SK_ARRAY_COUNT(gRec); ++i) {
+        clear_4x4_pixels(dstPixels);
+
+        dstInfo.fWidth = gRec[i].fRequestedDstSize.width();
+        dstInfo.fHeight = gRec[i].fRequestedDstSize.height();
+        bool success = srcBM.readPixels(dstInfo, dstPixels, rowBytes,
+                                        gRec[i].fRequestedSrcLoc.x(), gRec[i].fRequestedSrcLoc.y());
+        
+        REPORTER_ASSERT(reporter, gRec[i].fExpectedSuccess == success);
+        if (success) {
+            const SkIRect srcR = gRec[i].fExpectedSrcR;
+            const int dstX = gRec[i].fExpectedDstLoc.x();
+            const int dstY = gRec[i].fExpectedDstLoc.y();
+            // Walk the dst pixels, and check if we got what we expected
+            for (int y = 0; y < H; ++y) {
+                for (int x = 0; x < W; ++x) {
+                    SkPMColor dstC = dstPixels[y*4+x];
+                    // get into src coordinates
+                    int sx = x - dstX + srcR.x();
+                    int sy = y - dstY + srcR.y();
+                    if (srcR.contains(sx, sy)) {
+                        REPORTER_ASSERT(reporter, check_4x4_pixel(dstC, sx, sy));
+                    } else {
+                        REPORTER_ASSERT(reporter, 0 == dstC);
+                    }
+                }
+            }
+        }
+    }
+}
+