Add SkImageGenerator Interface

src/images/SkDecodingImageGenerator.h

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkDecodingImageGenerator_DEFINED
+#define SkDecodingImageGenerator_DEFINED
+
+#include "SkImageGenerator.h"
+
+class SkBitmap;
+
+/**
+ * Calls into SkImageDecoder::DecodeMemoryToTarget to implement a
+ * SkImageGenerator
+ */
+class SkDecodingImageGenerator : public SkImageGenerator {
+public:
+    /*
+     * The constructor will take a reference to the SkData.
+     */
+    SkDecodingImageGenerator(SkData* data);
+    virtual ~SkDecodingImageGenerator();
+
+    /**
+     *  Return a ref to the encoded (i.e. compressed) representation,
+     *  of this data.  The caller is responsible for calling unref()
+     *  on the data when it is finished.
+     */
+    virtual SkData* refEncodedData() SK_OVERRIDE;
+
+    /**
+     *  Return some information about the image, allowing the owner fo

[scroggo, 2013/11/19 22:19:27]

of*

[hal.canary, 2013/11/20 00:07:10]

I'll remove the sub-class's redundant comments.

+     *  this ojbect to allocate pixels.

[scroggo, 2013/11/19 22:19:27]

object*

[hal.canary, 2013/11/20 00:07:10]

I'll remove the sub-class's redundant comments.

+     *
+     *  @return false if anything goes wrong.
+     */
+    virtual bool getInfo(SkImageInfo* info) SK_OVERRIDE;
+
+    /**
+     *  Decode into the given pixels, a block of memory of size at
+     *  least (info.fHeight - 1) * rowBytes + (info.fWidth *
+     *  bytesPerPixel)
+     *
+     *  @param info Should be identical to the info returned by
+     *         getInfo so that the implementation can confirm that the
+     *         caller knows what it is asking for (config, size).
+     *         This contract also allows the caller to specify

[scroggo, 2013/11/19 22:19:27]

These two sentences seem to say opposite things. The first says info should be
the same as the answer from getInfo, and the second seems to imply that info can
be different, and the implementation chooses.

Same comment applies to SkImageGenerator.h

[hal.canary, 2013/11/20 00:07:10]

It is up to the implmentation.

+     *         different output-configs, which the implementation can
+     *         decide to support or not.
+     *
+     *  @return false if anything goes wrong.
+     */
+    virtual bool getPixels(const SkImageInfo& info,
+                           void* pixels,
+                           size_t rowBytes) SK_OVERRIDE;
+
+    /**
+     *  Install the SkData into the destination bitmap, using a new
+     *  SkDiscardablePixelRef and a new SkDecodingImageGenerator.
+     */
+    static bool Install(SkData* data, SkBitmap* destination);
+
+private:
+    SkData* fData;
+};
+#endif  // SkDecodingImageGenerator_DEFINED