SkJpegCodec

src/codec/SkJpegCodec.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkJpegCodec_DEFINED
+#define SkJpegCodec_DEFINED
+
+#include "SkCodec.h"
+#include "SkImageInfo.h"
+#include "SkJpegAutoClean.h"
+#include "SkStream.h"
+extern "C" {
+    #include "jpeglib.h"
+}
+
+/*
+ *
+ * This class implements the decoding for jpeg images
+ *
+ */
+class SkJpegCodec : public SkCodec {
+public:
+
+    /*
+     * Checks the start of the stream to see if the image is a jpeg
+     * Does not take ownership of the stream
+     */
+    static bool IsJpeg(SkStream*);
+
+    /*
+     * Assumes IsJpeg was called and returned true
+     * Creates a jpeg decoder
+     * Takes ownership of the stream
+     */
+    static SkCodec* NewFromStream(SkStream*);
+    
+
+protected:
+
+    /*
+     * Recommend a set of destination dimensions given a requested scale
+     */
+    SkISize onGetScaledDimensions(float desiredScale) const override;
+
+    /*
+     * Initiates the jpeg decode
+     */
+    Result onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes, const Options&,
+            SkPMColor*, int*) override;
+
+    SkEncodedFormat onGetEncodedFormat() const override {
+        return kJPEG_SkEncodedFormat;
+    }
+
+private:
+
+    /*
+     * Read enough of the stream to initialize the SkJpegCodec.
+     * Returns a bool representing success or failure.
+     *
+     * @param codecOut
+     * If it returned true, and codecOut was not NULL,
+     * codecOut will be set to a new SkJpegCodec.
+     *
+     * @param jpegInfoOut
+     * If it returned true, and codecOut was NULL,
+     * jpegInfoOut must be non-NULL and jpegInfoOut will be set to a new
+     * jpeg_decompress_struct pointer.
+     *
+     * @param stream
+     * Deleted on failure.
+     * codecOut will take ownership of it in the case where we created a codec.
+     * Ownership is unchanged when we return a jpegInfoOut.
+     *
+     */
+    static bool ReadHeader(SkStream* stream, SkCodec** codecOut,
+            jpeg_decompress_struct** jpegInfoOut);
+
+    /*
+     * Creates an instance of the decoder
+     * Called only by NewFromStream
+     *
+     * @param srcInfo contains the source width and height
+     * @param stream the encoded image data
+     */
+    SkJpegCodec(const SkImageInfo& srcInfo, SkStream* stream, jpeg_decompress_struct* jpegInfo);
+
+    JpegAutoClean fJpegInfo;
+
+    typedef SkCodec INHERITED;
+};
+
+#endif