Bmp Image Decoding

src/codec/SkCodec.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodec.h"
 #include "SkData.h"
+#include "SkCodec_libbmp.h"
 #include "SkCodec_libpng.h"
 #include "SkStream.h"
 
 SkCodec* SkCodec::NewFromStream(SkStream* stream) {
     if (!stream) {
         return NULL;
     }
     SkAutoTDelete<SkStream> streamDeleter(stream);
+    const bool isBmp = SkBmpCodec::IsBmp(stream);
+    if (!stream->rewind()) {
+        return NULL;
+    }
+    if (isBmp) {
+        streamDeleter.detach();
+        return SkBmpCodec::NewFromStream(stream);
+    }
     const bool isPng = SkPngCodec::IsPng(stream);

[scroggo, 2015/03/06 18:56:12]

nit: PNG should be first, since we'll see more PNG images.

That said, This function is going to quickly get out of hand. I think we should
take some advice from the old method in SkImageDecoder_Factory.

Something like:

struct DecoderProc {
  bool (*IsFormat)(SkStream*);
  SkCodec* (*NewFromStream)(SkStream*);
};

static const DecoderProc gDecoderProcs[] = {
  { SkPngCodec::IsPng, SkPngCodec::NewFromStream },
  { SkBmpCodec::IsBmp, SkBmpCodec::NewFromStream }
};

// Inside NewFromStream
for (proc in gDecoderProcs) {
  const bool correctFormat = proc.IsFormat(stream);
  if (!stream->rewind()) {
    return NULL;
  }
  if (correctFormat) {
    return proc.NewFromStream(stream);
  }
}
return NULL;

     if (!stream->rewind()) {
         return NULL;
     }
     if (isPng) {
         streamDeleter.detach();
         return SkPngCodec::NewFromStream(stream);
     }
     // TODO: Check other image types.
     return NULL;
 }
 
 SkCodec* SkCodec::NewFromData(SkData* data) {
     if (!data) {
         return NULL;
     }
     return NewFromStream(SkNEW_ARGS(SkMemoryStream, (data)));
 }
 
 SkCodec::SkCodec(const SkImageInfo& info, SkStream* stream)
     : fInfo(info)
     , fStream(stream)
     , fNeedsRewind(false)
 {}
 
 bool SkCodec::couldRewindIfNeeded() {
     // Store the value of fNeedsRewind so we can update it. Next read will
     // require a rewind.
     const bool neededRewind = fNeedsRewind;
     fNeedsRewind = true;

[msarett, 2015/03/05 23:13:17]

Why does this method set fNeedsRewind to true.  It doesn't affect bmp, I'm just
curious.

[scroggo, 2015/03/06 18:56:12]

I'm trying to make it so that a caller (for example a discardable pixel ref) can
decode multiple times (assuming the stream supports that).

This gets called in onGetPixels. If you call getPixels again, we will need to
rewind the stream. Setting it to true means the next call will require a rewind.

     return !neededRewind || fStream->rewind();
 }