Add scaled subset API to SkCodec

dm/DMSrcSink.cpp

Index: dm/DMSrcSink.cpp
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index 4137154e99ecc95b81e90d6791c45adf663a7c63..cf2a489a8712f37604a3d2309c65beb0c2e38132 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -249,7 +249,7 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
         return SkStringPrintf("Couldn't read %s.", fPath.c_str());
     }
     SkAutoTDelete<SkCodec> codec(NULL);
-    if (kScaledCodec_Mode == fMode) {
+    if (kScaledCodec_Mode == fMode || kSubset_Mode == fMode) {
         codec.reset(SkScaledCodec::NewFromData(encoded));
         // TODO (msarett): This should fall through to a fatal error once we support scaled
         //                 codecs for all image types.
@@ -512,12 +512,15 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
                                                       fPath.c_str(), W, H));
             }
             // subset dimensions
-            // SkWebpCodec, the only one that supports subsets, requires even top/left boundaries.
-            const int w = SkAlign2(W / divisor);
-            const int h = SkAlign2(H / divisor);
+            const int w = W / divisor;
+            const int h = H / divisor;
             SkIRect subset;
+            SkISize scaledSize;
+            SkIRect scaledSubset;
             SkCodec::Options opts;
             opts.fSubset = &subset;
+            opts.fScaledDimensions = &scaledSize;
+            opts.fScaledSubset = &scaledSubset;
             SkBitmap subsetBm;
             // We will reuse pixel memory from bitmap.
             void* pixels = bitmap.getPixels();
@@ -533,11 +536,10 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
                     const int preScaleH = SkTMin(h, H - y);
                     subset.setXYWH(x, y, preScaleW, preScaleH);
                     // And scale
-                    // FIXME: Should we have a version of getScaledDimensions that takes a subset
-                    // into account?
-                    decodeInfo = decodeInfo.makeWH(
-                            SkTMax(1, SkScalarRoundToInt(preScaleW * fScale)),
-                            SkTMax(1, SkScalarRoundToInt(preScaleH * fScale)));
+                    if (!codec->getScaledSubsetDimensions(fScale, opts)) {
+                        return Error::Nonfatal("Subsetting not supported.\n");
+                    }
+                    decodeInfo = decodeInfo.makeWH(scaledSubset.width(), scaledSubset.height());
                     size_t rowBytes = decodeInfo.minRowBytes();
                     if (!subsetBm.installPixels(decodeInfo, pixels, rowBytes, colorTable.get(),
                                                 nullptr, nullptr)) {
@@ -551,18 +553,11 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
                             break;
                         case SkCodec::kInvalidConversion:
                             if (0 == (x|y)) {
-                                // First subset is okay to return unimplemented.
+                                // First subset is okay to return invalid conversion.
                                 return Error::Nonfatal("Incompatible colortype conversion");
                             }
                             // If the first subset succeeded, a later one should not fail.
                             // fall through to failure
-                        case SkCodec::kUnimplemented:
-                            if (0 == (x|y)) {
-                                // First subset is okay to return unimplemented.
-                                return Error::Nonfatal("subset codec not supported");
-                            }
-                            // If the first subset succeeded, why would a later one fail?
-                            // fall through to failure
                         default:
                             return SkStringPrintf("subset codec failed to decode (%d, %d, %d, %d) "
                                                   "from %s with dimensions (%d x %d)\t error %d",
@@ -586,7 +581,7 @@ SkISize CodecSrc::size() const {
     SkAutoTUnref<SkData> encoded(SkData::NewFromFileName(fPath.c_str()));
     SkAutoTDelete<SkCodec> codec(nullptr);
 
-    if (kScaledCodec_Mode == fMode) {
+    if (kScaledCodec_Mode == fMode || kSubset_Mode == fMode) {
         codec.reset(SkScaledCodec::NewFromData(encoded));
     } else {
         codec.reset(SkCodec::NewFromData(encoded));