components/webp_transcode/webp_decoder.h

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef COMPONENTS_WEBP_TRANSCODE_WEBP_DECODER_H_
   6 #define COMPONENTS_WEBP_TRANSCODE_WEBP_DECODER_H_
   7
   8 #import <Foundation/Foundation.h>
   9
  10 #include "base/mac/scoped_nsobject.h"
  11 #include "base/memory/ref_counted.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "third_party/libwebp/webp/decode.h"
  14
  15 @class NSData;
  16
  17 namespace webp_transcode {
  18
  19 // Decodes a WebP image into either JPEG, PNG or uncompressed TIFF.
  20 class WebpDecoder : public base::RefCountedThreadSafe<WebpDecoder> {
  21  public:
  22   // Format of the decoded image.
  23   // This enum is used for UMA reporting, keep it in sync with the histogram
  24   // definition.
  25   enum DecodedImageFormat { JPEG = 1, PNG, TIFF, DECODED_FORMAT_COUNT };
  26
  27   class Delegate : public base::RefCountedThreadSafe<WebpDecoder::Delegate> {
  28    public:
  29     virtual void OnFinishedDecoding(bool success) = 0;
  30     virtual void SetImageFeatures(size_t total_size,  // In bytes.
  31                                   DecodedImageFormat format) = 0;
  32     virtual void OnDataDecoded(NSData* data) = 0;
  33
  34    protected:
  35     friend class base::RefCountedThreadSafe<WebpDecoder::Delegate>;
  36     virtual ~Delegate() {}
  37   };
  38
  39   explicit WebpDecoder(WebpDecoder::Delegate* delegate);
  40
  41   // For tests.
  42   static size_t GetHeaderSize();
  43
  44   // Main entry point.
  45   void OnDataReceived(const base::scoped_nsobject<NSData>& data);
  46
  47   // Stops the decoding.
  48   void Stop();
  49
  50  private:
  51   struct WebPIDecoderDeleter {
  52     inline void operator()(WebPIDecoder* ptr) const { WebPIDelete(ptr); }
  53   };
  54
  55   enum State { READING_FEATURES, READING_DATA, DONE };
  56
  57   friend class base::RefCountedThreadSafe<WebpDecoder>;
  58   virtual ~WebpDecoder();
  59
  60   // Implements WebP image decoding state machine steps.
  61   void DoReadFeatures(NSData* data);
  62   void DoReadData(NSData* data);
  63   bool DoSendData();
  64
  65   scoped_refptr<WebpDecoder::Delegate> delegate_;
  66   WebPDecoderConfig config_;
  67   WebpDecoder::State state_;
  68   scoped_ptr<WebPIDecoder, WebPIDecoderDeleter> incremental_decoder_;
  69   base::scoped_nsobject<NSData> output_buffer_;
  70   base::scoped_nsobject<NSMutableData> features_;
  71   int has_alpha_;
  72 };
  73
  74 }  // namespace webp_transcode
  75
  76 #endif  // COMPONENTS_WEBP_TRANSCODE_WEBP_DECODER_H_