Add subsetting to SkScaledCodec

tools/SkBitmapRegionCanvas.cpp

Index: tools/SkBitmapRegionCanvas.cpp
diff --git a/tools/SkBitmapRegionCanvas.cpp b/tools/SkBitmapRegionCanvas.cpp
index 086ac19864b3a15e96dae61d26a835eca43cb269..0ed95cbe1528de7d3edd4356ffd0bbece7804de9 100644
--- a/tools/SkBitmapRegionCanvas.cpp
+++ b/tools/SkBitmapRegionCanvas.cpp
@@ -6,7 +6,9 @@
  */
 
 #include "SkBitmapRegionCanvas.h"
+#include "SkBitmapRegionDecoderPriv.h"
 #include "SkCanvas.h"
+#include "SkCodecPriv.h"
 
 SkBitmapRegionCanvas::SkBitmapRegionCanvas(SkCodec* decoder)
     : INHERITED(decoder->getInfo().width(), decoder->getInfo().height())
@@ -14,36 +16,6 @@ SkBitmapRegionCanvas::SkBitmapRegionCanvas(SkCodec* decoder)
 {}
 
 /*
- * Chooses the correct image subset offsets and dimensions for the partial decode.
- */
-static inline void set_subset_region(int inputOffset, int inputDimension,
-        int imageOriginalDimension, int* imageSubsetOffset, int* outOffset,
-        int* imageSubsetDimension) {
-
-    // This must be at least zero, we can't start decoding the image at a negative coordinate.
-    *imageSubsetOffset = SkTMax(0, inputOffset);
-
-    // If inputOffset is less than zero, we decode to an offset location in the output bitmap.
-    *outOffset = *imageSubsetOffset - inputOffset;
-
-    // Use imageSusetOffset to make sure we don't decode pixels past the edge of the image.
-    // Use outOffset to make sure we don't decode pixels past the edge of the region.
-    *imageSubsetDimension = SkTMin(imageOriginalDimension - *imageSubsetOffset,
-            inputDimension - *outOffset);
-}
-
-/*
- * Returns a scaled dimension based on the original dimension and the sample size.
- * TODO: Share this implementation with SkScaledCodec.
- */
-static int get_scaled_dimension(int srcDimension, int sampleSize) {
-    if (sampleSize > srcDimension) {
-        return 1;
-    }
-    return srcDimension / sampleSize;
-}
-
-/*
  * Three differences from the Android version:
  *     Returns a Skia bitmap instead of an Android bitmap.
  *     Android version attempts to reuse a recycled bitmap.
@@ -56,10 +28,15 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
                                              SkColorType dstColorType) {
     // Reject color types not supported by this method
     if (kIndex_8_SkColorType == dstColorType || kGray_8_SkColorType == dstColorType) {
-        SkDebugf("Error: Color type not supported.\n");
+        SkCodecPrintf("Error: Color type not supported.\n");
         return nullptr;
     }
 
+    // Fix the input sampleSize if necessary.
+    if (sampleSize < 1) {
+        sampleSize = 1;
+    }
+
     // The client may not necessarily request a region that is fully within
     // the image.  We may need to do some calculation to determine what part
     // of the image to decode.
@@ -79,7 +56,8 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     // bitmap.  If the region is not fully contained within the image, this
     // will not be the same as inputWidth.
     int imageSubsetWidth;
-    set_subset_region(inputX, inputWidth, this->width(), &imageSubsetX, &outX, &imageSubsetWidth);
+    bool imageContainsEntireSubset = set_subset_region(inputX, inputWidth, this->width(),
+            &imageSubsetX, &outX, &imageSubsetWidth);
 
     // The top offset of the portion of the image we want, where zero
     // indicates the top edge of the image.
@@ -96,11 +74,11 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     // bitmap.  If the region is not fully contained within the image, this
     // will not be the same as inputHeight.
     int imageSubsetHeight;
-    set_subset_region(inputY, inputHeight, this->height(), &imageSubsetY, &outY,
-            &imageSubsetHeight);
+    imageContainsEntireSubset &= set_subset_region(inputY, inputHeight, this->height(),
+            &imageSubsetY, &outY, &imageSubsetHeight);
 
     if (imageSubsetWidth <= 0 || imageSubsetHeight <= 0) {
-        SkDebugf("Error: Region must intersect part of the image.\n");
+        SkCodecPrintf("Error: Region must intersect part of the image.\n");
         return nullptr;
     }
 
@@ -111,11 +89,11 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     }
     SkImageInfo decodeInfo = SkImageInfo::Make(this->width(), this->height(),
             dstColorType, dstAlphaType);
-    
+
     // Start the scanline decoder
     SkCodec::Result r = fDecoder->startScanlineDecode(decodeInfo);
     if (SkCodec::kSuccess != r) {
-        SkDebugf("Error: Could not start scanline decoder.\n");
+        SkCodecPrintf("Error: Could not start scanline decoder.\n");
         return nullptr;
     }
 
@@ -123,13 +101,13 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     SkBitmap tmp;
     SkImageInfo tmpInfo = decodeInfo.makeWH(this->width(), imageSubsetHeight);
     if (!tmp.tryAllocPixels(tmpInfo)) {
-        SkDebugf("Error: Could not allocate pixels.\n");
+        SkCodecPrintf("Error: Could not allocate pixels.\n");
         return nullptr;
     }
 
     // Skip the unneeded rows
     if (!fDecoder->skipScanlines(imageSubsetY)) {
-        SkDebugf("Error: Failed to skip scanlines.\n");
+        SkCodecPrintf("Error: Failed to skip scanlines.\n");
         return nullptr;
     }
 
@@ -144,7 +122,7 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     SkAutoTDelete<SkBitmap> bitmap(new SkBitmap());
     SkImageInfo dstInfo = decodeInfo.makeWH(outWidth, outHeight);
     if (!bitmap->tryAllocPixels(dstInfo)) {
-        SkDebugf("Error: Could not allocate pixels.\n");
+        SkCodecPrintf("Error: Could not allocate pixels.\n");
         return nullptr;
     }
 
@@ -155,9 +133,7 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     // TODO (msarett): This could be skipped if memory is zero initialized.
     //                 This would matter if this code is moved to Android and
     //                 uses Android bitmaps.
-    if (0 != outX || 0 != outY ||
-            inputX + inputWidth > this->width() ||
-            inputY + inputHeight > this->height()) {
+    if (!imageContainsEntireSubset) {
         bitmap->eraseColor(0);
     }
 
@@ -177,3 +153,15 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
 
     return bitmap.detach();
 }
+
+bool SkBitmapRegionCanvas::conversionSupported(SkColorType colorType) {
+    // SkCanvas does not draw to these color types.
+    if (kIndex_8_SkColorType == colorType || kGray_8_SkColorType == colorType) {
+        return false;
+    }
+
+    // FIXME: Call virtual function when it lands.
+    SkImageInfo info = SkImageInfo::Make(0, 0, colorType, fDecoder->getInfo().alphaType(),
+            fDecoder->getInfo().profileType());
+    return conversion_possible(info, fDecoder->getInfo());
+}