DM testing for skipping and scaling

dm/DMSrcSink.cpp

Index: dm/DMSrcSink.cpp
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index 0a90e03103dc23b087a3269f24434ec925f90d05..940a646063525769c89f12764620799429759350 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -64,10 +64,11 @@ void GMSrc::modifyGrContextOptions(GrContextOptions* options) const {
 
 /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
 
-CodecSrc::CodecSrc(Path path, Mode mode, DstColorType dstColorType)
+CodecSrc::CodecSrc(Path path, Mode mode, DstColorType dstColorType, float scale)
     : fPath(path)
     , fMode(mode)
     , fDstColorType(dstColorType)
+    , fScale(scale)
 {}
 
 Error CodecSrc::draw(SkCanvas* canvas) const {
@@ -195,7 +196,7 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
             * subsetBm's size is determined based on the current subset and may be larger for end
             * subsets.
             */
-            SkImageInfo largestSubsetDecodeInfo = 
+            SkImageInfo largestSubsetDecodeInfo =
                     decodeInfo.makeWH(subsetWidth + extraX, subsetHeight + extraY);
             SkBitmap largestSubsetBm;
             if (!largestSubsetBm.tryAllocPixels(largestSubsetDecodeInfo, NULL, colorTable.get())) {
@@ -226,7 +227,7 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
                         }
                     }
                     //skip to first line of subset
-                    const SkImageGenerator::Result skipResult = 
+                    const SkImageGenerator::Result skipResult =
                             subsetScanlineDecoder->skipScanlines(y);
                     switch (skipResult) {
                         case SkImageGenerator::kSuccess:
@@ -262,6 +263,57 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
             }
             break;
         }
+        // This mode tests scaling and skipping.  The decode is performed for the scaled image
+        // dimensions using stripes.

[scroggo, 2015/06/11 15:50:02]

It is curious to me that we combine scaling with stripes. Maybe stripes should
be a separate mode?

On a related note, I can imagine a couple of ways to do scaling:
- use the dimensions from getScaledDimensions
  - jpeg will support scaling (although maybe not to the exact dimensions we
want)
- others may not (e.g. png). we should have some sort of fallback (which can
also be used if jpeg is not exact)
  - I don't know whether the fallback should be a separate case or not.

[msarett, 2015/06/11 19:29:36]

Yes this was an odd decision that didn't make much sense.  This has been
redesigned.

+        case kScale_Mode: {
+            SkISize size = codec->getScaledDimensions(fScale);
+            SkImageInfo info = decodeInfo.makeWH(size.width(), size.height());
+            int width = info.width();
+            int height = info.height();
+            // This value is chosen arbitrarily.  We exercise more cases by choosing a value that
+            // does not align with image blocks.
+            const int stripeHeight = 37;
+            const int numStripes = (height + stripeHeight - 1) / stripeHeight;
+
+            // Create bitmap
+            SkBitmap bitmap;
+            if (!bitmap.tryAllocPixels(info, NULL, colorTable.get())) {
+                return SkStringPrintf("Cannot allocate pixels for %s %dx%d", fPath.c_str(),
+                        width, height);
+            }
+
+            // Decode odd stripes
+            SkScanlineDecoder* decoder = codec->getScanlineDecoder(info, NULL, colorPtr,
+                    colorCountPtr);
+            if (NULL == decoder) {
+                return Error::Nonfatal("Cannot use scanline decoder for all images");
+            }
+            for (int i = 0; i < numStripes; i += 2) {
+                // Skip a stripe
+                const int linesToSkip = SkTMin(stripeHeight, height - i * stripeHeight);
+                decoder->skipScanlines(linesToSkip);
+
+                // Read a stripe
+                const int startY = SkTMin((i + 1) * stripeHeight, height - 1);
+                const int linesToRead = SkTMax(0, SkTMin(stripeHeight, height - startY));
+                decoder->getScanlines(bitmap.getAddr(0, startY), linesToRead, bitmap.rowBytes());
+            }
+
+            // Decode even stripes
+            decoder = codec->getScanlineDecoder(info, NULL, colorPtr, colorCountPtr);
+            for (int i = 0; i < numStripes; i += 2) {
+                // Read a stripe
+                const int startY = i * stripeHeight;
+                const int linesToRead = SkTMin(stripeHeight, height - startY);
+                decoder->getScanlines(bitmap.getAddr(0, startY), linesToRead, bitmap.rowBytes());
+
+                // Skip a stripe
+                const int linesToSkip = SkTMax(0, SkTMin(stripeHeight,
+                        height - (i + 1) * stripeHeight));
+                decoder->skipScanlines(linesToSkip);
+            }
+            canvas->drawBitmap(bitmap, 0, 0);
+        }
     }
     return "";
 }
@@ -270,14 +322,19 @@ SkISize CodecSrc::size() const {
     SkAutoTUnref<SkData> encoded(SkData::NewFromFileName(fPath.c_str()));
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(encoded));
     if (NULL != codec) {
-        return codec->getInfo().dimensions();
+        SkISize size = codec->getScaledDimensions(fScale);

[scroggo, 2015/06/11 15:50:02]

For png (for example) this will return the original size. Not sure this is
useful.

[msarett, 2015/06/11 19:29:36]

We are now returning Error::Nonfatal for tests where fScale is not 1.0 and the
scaled dims are not different from the original dims.  I hope that clears up
this concern.

+        return size;
     } else {
         return SkISize::Make(0, 0);
     }
 }
 
 Name CodecSrc::name() const {
-    return SkOSPath::Basename(fPath.c_str());
+    if (1.0f == fScale) {
+        return SkOSPath::Basename(fPath.c_str());
+    } else {
+        return SkStringPrintf("%s_%.3f", SkOSPath::Basename(fPath.c_str()).c_str(), fScale);
+    }
 }
 
 /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/