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