Use new jpeg_crop_scanlines() API to optimize jpeg subset decodes

dm/DM.cpp

Index: dm/DM.cpp
diff --git a/dm/DM.cpp b/dm/DM.cpp
index c8b65842d042f660abbf5614407b99fa46e0399d..6b94f83ae1d4b26b0b33053e9c394842d624dd45 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -239,8 +239,8 @@ static void push_codec_src(Path path, CodecSrc::Mode mode, CodecSrc::DstColorTyp
         case CodecSrc::kScanline_Mode:
             folder.append("scanline");
             break;
-        case CodecSrc::kStripe_Mode:
-            folder.append("stripe");
+        case CodecSrc::kTile_Mode:
+            folder.append("tile");
             break;
         case CodecSrc::kSubset_Mode:
             folder.append("codec_subset");
@@ -346,9 +346,26 @@ static void push_codec_srcs(Path path) {
     // SkJpegCodec natively supports scaling to: 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875
     const float nativeScales[] = { 0.125f, 0.25f, 0.375f, 0.5f, 0.625f, 0.750f, 0.875f, 1.0f };
 
-    const CodecSrc::Mode nativeModes[] = { CodecSrc::kCodec_Mode, CodecSrc::kCodecZeroInit_Mode,
-            CodecSrc::kScanline_Mode, CodecSrc::kStripe_Mode, CodecSrc::kSubset_Mode,
-            CodecSrc::kGen_Mode };
+    CodecSrc::Mode nativeModes[5];

[scroggo, 2016/02/22 15:55:03]

nit: As long as you're rewriting this code, why not use an SkTArray like
alphaModes does, down below. Then you don't need to worry about using the
correct index/size.

[msarett, 2016/02/22 17:38:15]

Agreed that's better.  I'll fix the color types as well.

+    nativeModes[0] = CodecSrc::kCodec_Mode;
+    nativeModes[1] = CodecSrc::kCodecZeroInit_Mode;
+    nativeModes[2] = CodecSrc::kGen_Mode;
+    uint32_t numNativeModes;
+    switch (codec->getEncodedFormat()) {
+        case SkEncodedFormat::kJPEG_SkEncodedFormat:
+            nativeModes[3] = CodecSrc::kScanline_Mode;
+            nativeModes[4] = CodecSrc::kTile_Mode;
+            numNativeModes = 5;
+            break;
+        case SkEncodedFormat::kWEBP_SkEncodedFormat:
+            nativeModes[3] = CodecSrc::kSubset_Mode;
+            numNativeModes = 4;
+            break;
+        default:
+            nativeModes[3] = CodecSrc::kScanline_Mode;
+            numNativeModes = 4;
+            break;
+    }
 
     CodecSrc::DstColorType colorTypes[3];
     uint32_t numColorTypes;
@@ -381,15 +398,15 @@ static void push_codec_srcs(Path path) {
         alphaModes.push_back(kOpaque_SkAlphaType);
     }
 
-    for (CodecSrc::Mode mode : nativeModes) {
+    for (uint32_t j = 0; j < numNativeModes; j++) {
         // SkCodecImageGenerator only runs for the default colorType
         // recommended by SkCodec.  There is no need to generate multiple
         // tests for different colorTypes.
         // TODO (msarett): Add scaling support to SkCodecImageGenerator.
-        if (CodecSrc::kGen_Mode == mode) {
+        if (CodecSrc::kGen_Mode == nativeModes[j]) {
             // FIXME: The gpu backend does not draw kGray sources correctly. (skbug.com/4822)
             if (kGray_8_SkColorType != codec->getInfo().colorType()) {
-                push_codec_src(path, mode, CodecSrc::kGetFromCanvas_DstColorType,
+                push_codec_src(path, CodecSrc::kGen_Mode, CodecSrc::kGetFromCanvas_DstColorType,
                                codec->getInfo().alphaType(), 1.0f);
             }
             continue;
@@ -398,7 +415,7 @@ static void push_codec_srcs(Path path) {
         for (float scale : nativeScales) {
             for (uint32_t i = 0; i < numColorTypes; i++) {
                 for (SkAlphaType alphaType : alphaModes) {
-                    push_codec_src(path, mode, colorTypes[i], alphaType, scale);
+                    push_codec_src(path, nativeModes[j], colorTypes[i], alphaType, scale);
                 }
             }
         }