Add subsetting to SkScanlineDecoder

dm/DMSrcSink.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "DMSrcSink.h"
 #include "SamplePipeControllers.h"
 #include "SkCodec.h"
@@ skipping 382 matching lines @@
             * subsets.
             */
             SkImageInfo largestSubsetDecodeInfo =
                     decodeInfo.makeWH(subsetWidth + extraX, subsetHeight + extraY);
             SkBitmap largestSubsetBm;
             if (!largestSubsetBm.tryAllocPixels(largestSubsetDecodeInfo, nullptr,
                     colorTable.get())) {
                 return SkStringPrintf("Image(%s) is too large (%d x %d)\n", fPath.c_str(),
                         largestSubsetDecodeInfo.width(), largestSubsetDecodeInfo.height());
             }
-            const size_t rowBytes = decodeInfo.minRowBytes();
-            char* buffer = new char[largestSubsetDecodeInfo.height() * rowBytes];
-            SkAutoTDeleteArray<char> lineDeleter(buffer);
             for (int col = 0; col < divisor; col++) {
                 //currentSubsetWidth may be larger than subsetWidth for rightmost subsets
                 const int currentSubsetWidth = (col + 1 == divisor) ?
                         subsetWidth + extraX : subsetWidth;
                 const int x = col * subsetWidth;
                 for (int row = 0; row < divisor; row++) {
                     //currentSubsetHeight may be larger than subsetHeight for bottom subsets
                     const int currentSubsetHeight = (row + 1 == divisor) ?
                             subsetHeight + extraY : subsetHeight;
                     const int y = row * subsetHeight;
                     //create scanline decoder for each subset
-                    if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, NULL, colorPtr,
-                                                                        colorCountPtr)
-                            // TODO (msarett): Support this mode for all scanline orderings.
-                            || SkCodec::kTopDown_SkScanlineOrder != codec->getScanlineOrder()) {
+                    SkCodec::Options options;
+                    SkIRect subset = SkIRect::MakeXYWH(x, 0, currentSubsetWidth, h);
+                    options.fSubset = &subset;
+                    // TODO (msarett): Support this mode for all scanline orderings.
+                    if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, &options,
+                            colorPtr, colorCountPtr) ||
+                            SkCodec::kTopDown_SkScanlineOrder != codec->getScanlineOrder()) {
                         if (x == 0 && y == 0) {
                             //first try, image may not be compatible
                             return Error::Nonfatal("Could not start top-down scanline decoder");
                         } else {
                             return "Error scanline decoder is nullptr";
                         }
                     }
                     // Skip to the first line of subset.  We ignore the result value here.
                     // If the skip value fails, this will indicate an incomplete image.
                     // This means that the call to getScanlines() will also fail, but it
                     // will fill the buffer with a default value, so we can still draw the
                     // image.
                     codec->skipScanlines(y);
 
                     //create and set size of subsetBm
                     SkBitmap subsetBm;
                     SkIRect bounds = SkIRect::MakeWH(currentSubsetWidth, currentSubsetHeight);
                     SkAssertResult(largestSubsetBm.extractSubset(&subsetBm, bounds));
-                    SkAutoLockPixels autlockSubsetBm(subsetBm, true);
-                    codec->getScanlines(buffer, currentSubsetHeight, rowBytes);
-
-                    const size_t bpp = decodeInfo.bytesPerPixel();
-                    char* bufferRow = buffer;
-                    for (int subsetY = 0; subsetY < currentSubsetHeight; ++subsetY) {
-                        memcpy(subsetBm.getAddr(0, subsetY), bufferRow + x*bpp,
-                                currentSubsetWidth*bpp);
-                        bufferRow += rowBytes;
-                    }
-
+                    SkAutoLockPixels autolock(subsetBm, true);
+                    codec->getScanlines(subsetBm.getAddr(0, 0), currentSubsetHeight,
+                            subsetBm.rowBytes());
                     subsetBm.notifyPixelsChanged();
                     canvas->drawBitmap(subsetBm, SkIntToScalar(x), SkIntToScalar(y));
                 }
             }
             break;
         }
         case kStripe_Mode: {
             const int height = decodeInfo.height();
             // This value is chosen arbitrarily.  We exercise more cases by choosing a value that
             // does not align with image blocks.
@@ skipping 744 matching lines @@
             skr.visit<void>(i, drawsAsSingletonPictures);
         }
         SkAutoTUnref<SkPicture> macroPic(macroRec.endRecordingAsPicture());
 
         canvas->drawPicture(macroPic);
         return "";
     });
 }
 
 }  // namespace DM