SkScaledCodec class

This class does scaling by using a scanlineDecoder.
getScanlines and skipScanlines are used for y sampling,
the swizzler is used for x sampling

this class is currently only working for png and jpeg images
I will update other Codec types to work soon

For SkJpegCodec to implement width wise swizzling it now
uses a swizzler. I ran performance tests on this change.
Here are the performance test results:
https://docs.google.com/a/google.com/spreadsheets/d/1D7-Q_GXD_dI68LZO005NNvb8Wq2Ee0wEBEPG72671yw/edit?usp=sharing

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/0944100ac89f797714eeae0cf2875e2335ff52ee

Committed: https://skia.googlesource.com/skia/+/d518ea7927f9f4e0ed5b4134d1b4f48243855a47

Committed: https://skia.googlesource.com/skia/+/b157917507d4f7d2651f0aeb566d31603cc02240

Review URL: https://codereview.chromium.org/1260673002

2 files changed, 22 insertions, 9 deletions

diff --git a/dm/DM.cpp b/dm/DM.cpp
index 9dcdff1a0f..fe096434c6 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -212,7 +212,12 @@ static void push_codec_srcs(Path path) {
     // TODO (msarett): Add more scaling tests as we implement more flexible scaling.
     // TODO (msarett): Implement scaling tests for SkImageDecoder in order to compare with these
     //                 tests.  SkImageDecoder supports downscales by integer factors.
-    const float scales[] = { 0.125f, 0.25f, 0.375f, 0.5f, 0.625f, 0.750f, 0.875f, 1.0f };
+    // SkJpegCodec natively supports scaling to: 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875
+    // 0.1, 0.16, 0.2 etc allow us to test SkScaledCodec with sampleSize 10, 6, 5, etc
+    // 0.4, 0.7 etc allow to test what happens when the client requests a scale that
+    // does not exactly match a sampleSize or native scaling capability
+    const float scales[] = { 0.1f, 0.125f, 0.166f, 0.2f, 0.25f, 0.333f, 0.375f, 0.4f, 0.5f, 0.6f,
+                             0.625f, 0.750f, 0.8f, 0.875f, 1.0f };
 
     for (float scale : scales) {
         if (scale != 1.0f && (path.endsWith(".webp") || path.endsWith(".WEBP"))) {
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index f555b9fcbd..9826f97822 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -27,6 +27,7 @@
 #include "SkScanlineDecoder.h"
 #include "SkStream.h"
 #include "SkXMLWriter.h"
+#include "SkScaledCodec.h"
 
 DEFINE_bool(multiPage, false, "For document-type backends, render the source"
             " into multiple pages");
@@ -84,9 +85,13 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
     if (!encoded) {
         return SkStringPrintf("Couldn't read %s.", fPath.c_str());
     }
-    SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(encoded));
+    SkAutoTDelete<SkCodec> codec(SkScaledCodec::NewFromData(encoded));
     if (NULL == codec.get()) {
-        return SkStringPrintf("Couldn't create codec for %s.", fPath.c_str());
+        // scaledCodec not supported, try normal codec
+        codec.reset(SkCodec::NewFromData(encoded));
+        if (NULL == codec.get()) {
+            return SkStringPrintf("Couldn't create codec for %s.", fPath.c_str());
+        }
     }
 
     // Choose the color type to decode to
@@ -446,13 +451,16 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
 
 SkISize CodecSrc::size() const {
     SkAutoTUnref<SkData> encoded(SkData::NewFromFileName(fPath.c_str()));
-    SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(encoded));
-    if (NULL != codec) {
-        SkISize size = codec->getScaledDimensions(fScale);
-        return size;
-    } else {
-        return SkISize::Make(0, 0);
+    SkAutoTDelete<SkCodec> codec(SkScaledCodec::NewFromData(encoded));
+    if (NULL == codec) {
+        // scaledCodec not supported, try regular codec
+        codec.reset(SkCodec::NewFromData(encoded));
+        if (NULL == codec) {
+            return SkISize::Make(0, 0);
+        }
     }
+    SkISize size = codec->getScaledDimensions(fScale);
+    return size;
 }
 
 Name CodecSrc::name() const {