SkScaledCodec class

src/codec/SkJpegCodec.cpp

Index: src/codec/SkJpegCodec.cpp
diff --git a/src/codec/SkJpegCodec.cpp b/src/codec/SkJpegCodec.cpp
index 84e90d444249142d69a68cd52cab59cebb37c30a..ed58f65f50044a4b96c423db993210a1e8b7e0e1 100644
--- a/src/codec/SkJpegCodec.cpp
+++ b/src/codec/SkJpegCodec.cpp
@@ -11,6 +11,7 @@
 #include "SkJpegUtility_codec.h"
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
+#include "SkScaledCodec.h"
 #include "SkScanlineDecoder.h"
 #include "SkStream.h"
 #include "SkTemplates.h"
@@ -189,6 +190,41 @@ SkISize SkJpegCodec::onGetScaledDimensions(float desiredScale) const {
     return SkISize::Make(dinfo.output_width, dinfo.output_height);
 }
 
+SkCodec::Result SkJpegCodec::initializeSwizzler(const SkImageInfo& requestedInfo,

[scroggo, 2015/07/31 19:31:58]

It looks like the swizzler is never used in getPixels? That's probably correct
(it's only used for sampling in X), but maybe add comments explaining that?

[emmaleer, 2015/07/31 20:43:10]

Acknowledged.

+                                               void* dst, size_t rowBytes,
+                                               const Options& options,
+                                               SkPMColor ctable[],
+                                               int* ctableCount) {
+
+    const SkColorType srcColorType = requestedInfo.colorType();
+    SkSwizzler::SrcConfig srcConfig;
+    switch (srcColorType) {
+        case kGray_8_SkColorType:
+            srcConfig = SkSwizzler::kGray;
+            break;
+        case kRGBA_8888_SkColorType:
+            srcConfig = SkSwizzler::kRGBX;
+            break;
+        case kBGRA_8888_SkColorType:
+            srcConfig = SkSwizzler::kBGRX;
+            break;
+        case kRGB_565_SkColorType:
+            srcConfig = SkSwizzler::kRGB_565;
+            break;
+        default:
+            //would have exited before now if the colorType was supported by jpeg
+            SkASSERT(false);
+    }
+
+    fSwizzler.reset(SkSwizzler::CreateSwizzler(srcConfig, NULL, requestedInfo,
+                                               options.fZeroInitialized, this->getInfo().width()));
+    if (!fSwizzler) {
+        // FIXME: CreateSwizzler could fail for another reason.
+        return kUnimplemented;
+    }
+    return kSuccess;
+}
+
 /*
  * Handles rewinding the input stream if it is necessary
  */
@@ -287,6 +323,9 @@ bool SkJpegCodec::scaleToDimensions(uint32_t dstWidth, uint32_t dstHeight) {
         if (1 == fDecoderMgr->dinfo()->scale_num ||
                 dstWidth > fDecoderMgr->dinfo()->output_width ||
                 dstHeight > fDecoderMgr->dinfo()->output_height) {
+            // reset scale settings on failure 

[scroggo, 2015/07/31 19:31:58]

Can you explain why? "because this may be supported by the swizzler." or
something like that.

Also, it seems like this is no longer a failure case?

I think the name of the function and its comments should probably be updated to
reflect that this now returns whether it can *natively* scale to these
dimensions.

[emmaleer, 2015/07/31 20:43:10]

Acknowledged.

+            this->fDecoderMgr->dinfo()->scale_num = 8;
+            turbo_jpeg_calc_output_dimensions(this->fDecoderMgr->dinfo());
             return fDecoderMgr->returnFalse("could not scale to requested dimensions");

[scroggo, 2015/07/31 19:31:58]

I wonder if this error message is necessary now that we will try a backup? (Or
maybe it should just be updated?)

[emmaleer, 2015/07/31 20:43:09]

I removed the error. I think it's okay for the function to return false, so it
should not be an error.

[scroggo, 2015/07/31 21:11:57]

Agreed for your case, although we should perhaps make the caller from
onGetPixels (which does not allow sampling) print this error message.

[emmaleer, 2015/08/03 14:29:41]

If the function fails onGetPixels already returns:
fDecoderMgr->returnFailure("cannot scale to requested dims", kInvalidScale);

[scroggo, 2015/08/03 17:02:55]

Ok, great, so this is fine to remove.

         }
 
@@ -394,7 +433,12 @@ public:
         : INHERITED(dstInfo)
         , fCodec(codec)
         , fOpts(opts)
-    {}
+    {
+        if(fCodec->fSwizzler) {
+            fStorage.reset(fCodec->getInfo().width() * dstInfo.minRowBytes());
+            fSrcRow = static_cast<uint8_t*>(fStorage.get());
+        }
+    }
 
     virtual ~SkJpegScanlineDecoder() {
         if (setjmp(fCodec->fDecoderMgr->getJmpBuf())) {
@@ -413,9 +457,16 @@ public:
         if (setjmp(fCodec->fDecoderMgr->getJmpBuf())) {
             return fCodec->fDecoderMgr->returnFailure("setjmp", SkCodec::kInvalidInput);
         }
-
         // Read rows one at a time
-        JSAMPLE* dstRow = (JSAMPLE*) dst;
+        JSAMPLE* dstRow;
+        if (fCodec->fSwizzler) {
+            // write data to storage row, then sample using swizzler         
+            dstRow = fSrcRow;
+        } else {
+            // write data directly to dst
+            dstRow = (JSAMPLE*) dst;
+        }
+
         for (int y = 0; y < count; y++) {
             // Read row of the image
             uint32_t rowsDecoded =
@@ -435,10 +486,14 @@ public:
                 convert_CMYK_to_RGBA(dstRow, this->dstInfo().width());
             }
 
-            // Move to the next row
-            dstRow = SkTAddOffset<JSAMPLE>(dstRow, rowBytes);
+            if(fCodec->fSwizzler) {
+                // use swizzler to sample row
+                fCodec->fSwizzler->swizzle(dst, dstRow);
+                dst = SkTAddOffset<JSAMPLE>(dst, rowBytes);
+            } else {
+                dstRow = SkTAddOffset<JSAMPLE>(dstRow, rowBytes);
+            }
         }
-
         return SkCodec::kSuccess;
     }
 
@@ -464,6 +519,8 @@ public:
 
 private:
     SkAutoTDelete<SkJpegCodec> fCodec;
+    SkAutoMalloc               fStorage;    // Only used if sampling is needed
+    uint8_t*                   fSrcRow;     // Only used if sampling is needed
     const SkCodec::Options&    fOpts;
 
     typedef SkScanlineDecoder INHERITED;
@@ -501,8 +558,17 @@ SkScanlineDecoder* SkJpegCodec::onGetScanlineDecoder(const SkImageInfo& dstInfo,
 
     // Perform the necessary scaling
     if (!codec->scaleToDimensions(dstInfo.width(), dstInfo.height())) {
-        SkCodecPrintf("Cannot scale to output dimensions\n");
-        return NULL;
+        // native scaling to dstInfo dimensions not supported
+
+        if (!SkScaledCodec::DimensionsSupportedForSampling(this->getInfo(), dstInfo)) {
+            return NULL;
+        }
+        // create swizzler for sampling
+        if (codec->initializeSwizzler(dstInfo, NULL, dstInfo.minRowBytes(), options, ctable,
+                                      ctableCount) != kSuccess) {
+            SkCodecPrintf("failed to initialize the swizzler.\n");
+            return NULL;
+        }
     }
 
     // Now, given valid output dimensions, we can start the decompress