Add SkCodec, including PNG implementation.

DM:
Add a flag to use SkCodec instead of SkImageDecoder.

SkCodec:
Base class for codecs, allowing creation from an SkStream or an SkData.
An SkCodec, on creation, knows properties of the data like its width and height. Further calls can be used to generate the image.
TODO: Add scanline iterator

SkPngCodec:
New decoder for png. Wraps libpng. The code has been repurposed from SkImageDecoder_libpng.
TODO: Handle other destination colortypes
TODO: Substitute the transpose color
TODO: Allow silencing warnings
TODO: Use RGB instead of filler?
TODO: sRGB

SkSwizzler:
Simplified version of SkScaledSampler. Unlike the sampler, this object does no sampling.
TODO: Implement other swizzles.

BUG=skia:3257

Review URL: https://codereview.chromium.org/930283002

1 files changed, 34 insertions, 0 deletions

diff --git a/src/codec/SkCodec_libpng.h b/src/codec/SkCodec_libpng.h
new file mode 100644
index 0000000000..a5327dda41
--- /dev/null
+++ b/src/codec/SkCodec_libpng.h
@@ -0,0 +1,34 @@
+/*
+ * 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 "SkImageInfo.h"
+
+extern "C" {
+    // FIXME: I'd like to force all platforms to use the same decoder, but this
+    // means an extra dependency on Mac/Win.
+    #include "png.h"
+}
+
+class SkStream;
+
+class SkPngCodec : public SkCodec {
+public:
+    // Assumes IsPng was called and returned true.
+    static SkCodec* NewFromStream(SkStream*);
+    static bool IsPng(SkStream*);
+protected:
+    Result onGetPixels(const SkImageInfo&, void*, size_t, SkPMColor*, int*) SK_OVERRIDE;
+private:
+    png_structp             fPng_ptr;
+    png_infop               fInfo_ptr;
+
+    SkPngCodec(const SkImageInfo&, SkStream*, png_structp, png_infop);
+    ~SkPngCodec();
+
+    typedef SkCodec INHERITED;
+};