Update Subset benches to support interlacing and fix bugs

bench/subset/SubsetZoomBench.cpp

Index: bench/subset/SubsetZoomBench.cpp
diff --git a/bench/subset/SubsetZoomBench.cpp b/bench/subset/SubsetZoomBench.cpp
index ffd86703ec2271e40fdc27c1679fe914f4b958ac..b2233c13b6dadb082b4affcfc6bcc8f2ac4154b9 100644
--- a/bench/subset/SubsetZoomBench.cpp
+++ b/bench/subset/SubsetZoomBench.cpp
@@ -63,7 +63,6 @@ void SubsetZoomBench::onDraw(int n, SkCanvas* canvas) {
             SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(fStream->duplicate()));
             const SkImageInfo info = codec->getInfo().makeColorType(fColorType);
             SkAutoTDeleteArray<uint8_t> row(new uint8_t[info.minRowBytes()]);
-            codec->startScanlineDecode(info, nullptr, colors, &colorCount);
 
             const int centerX = info.width() / 2;
             const int centerY = info.height() / 2;
@@ -81,12 +80,40 @@ void SubsetZoomBench::onDraw(int n, SkCanvas* canvas) {
                 alloc_pixels(&bitmap, subsetInfo, colors, colorCount);
 
                 uint32_t bpp = info.bytesPerPixel();
+
+                codec->startScanlineDecode(info, nullptr, colors, &colorCount);
                 codec->skipScanlines(subsetStartY);
-                for (int y = 0; y < subsetHeight; y++) {
-                    codec->getScanlines(row.get(), 1, 0);
-                    memcpy(bitmap.getAddr(0, y), row.get() + subsetStartX * bpp,
-                            subsetWidth * bpp);
+
+                switch (codec->getScanlineOrder()) {
+                    case SkCodec::kTopDown_SkScanlineOrder:
+                        for (int y = 0; y < subsetHeight; y++) {

[scroggo, 2015/10/06 20:36:04]

loop should be unchanged

[msarett, 2015/10/06 21:58:52]

Acknowledged.

+                            codec->getScanlines(row.get(), 1, 0);
+                            memcpy(bitmap.getAddr(0, y), row.get() + subsetStartX * bpp,
+                                    subsetWidth * bpp);
+                        }
+                        break;
+                    case SkCodec::kNone_SkScanlineOrder: {
+                        // decode all scanlines that intersect the subset, and copy the subset
+                        // into the output.
+                        SkImageInfo stripeInfo = info.makeWH(info.width(), subsetHeight);
+                        SkBitmap stripeBm;
+                        alloc_pixels(&stripeBm, stripeInfo, colors, colorCount);
+
+                        codec->getScanlines(stripeBm.getPixels(), subsetHeight,
+                                stripeBm.rowBytes());
+                        for (int y = 0; y < subsetHeight; y++) {
+                            memcpy(bitmap.getAddr(0, y),
+                                   stripeBm.getAddr(subsetStartX, y),
+                                   subsetWidth * bpp);
+                        }
+                        break;
+                    }
+                    default:
+                        // We currently are only testing kTopDown and kNone, which are the only
+                        // two used by the subsets we care about. skbug.com/4428
+                        SkASSERT(false);
                 }
+
                 w <<= 1;
                 h <<= 1;
             } while (w < 2 * info.width() || h < 2 * info.height());