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      1 // Copyright 2011 Google Inc. All Rights Reserved.
      2 //
      3 // This code is licensed under the same terms as WebM:
      4 //  Software License Agreement:  http://www.webmproject.org/license/software/
      5 //  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
      6 // -----------------------------------------------------------------------------
      7 //
      8 // Internal header: WebP decoding parameters and custom IO on buffer
      9 //
     10 // Author: somnath (at) google.com (Somnath Banerjee)
     11 
     12 #ifndef WEBP_DEC_WEBPI_H_
     13 #define WEBP_DEC_WEBPI_H_
     14 
     15 #if defined(__cplusplus) || defined(c_plusplus)
     16 extern "C" {
     17 #endif
     18 
     19 #include "../utils/rescaler.h"
     20 #include "./decode_vp8.h"
     21 
     22 //------------------------------------------------------------------------------
     23 // WebPDecParams: Decoding output parameters. Transient internal object.
     24 
     25 typedef struct WebPDecParams WebPDecParams;
     26 typedef int (*OutputFunc)(const VP8Io* const io, WebPDecParams* const p);
     27 typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos);
     28 
     29 struct WebPDecParams {
     30   WebPDecBuffer* output;             // output buffer.
     31   uint8_t* tmp_y, *tmp_u, *tmp_v;    // cache for the fancy upsampler
     32                                      // or used for tmp rescaling
     33 
     34   int last_y;                 // coordinate of the line that was last output
     35   const WebPDecoderOptions* options;  // if not NULL, use alt decoding features
     36   // rescalers
     37   WebPRescaler scaler_y, scaler_u, scaler_v, scaler_a;
     38   void* memory;                  // overall scratch memory for the output work.
     39 
     40   OutputFunc emit;               // output RGB or YUV samples
     41   OutputFunc emit_alpha;         // output alpha channel
     42   OutputRowFunc emit_alpha_row;  // output one line of rescaled alpha values
     43 };
     44 
     45 // Should be called first, before any use of the WebPDecParams object.
     46 void WebPResetDecParams(WebPDecParams* const params);
     47 
     48 //------------------------------------------------------------------------------
     49 // Header parsing helpers
     50 
     51 // Structure storing a description of the RIFF headers.
     52 typedef struct {
     53   const uint8_t* data;         // input buffer
     54   size_t data_size;            // input buffer size
     55   size_t offset;               // offset to main data chunk (VP8 or VP8L)
     56   const uint8_t* alpha_data;   // points to alpha chunk (if present)
     57   size_t alpha_data_size;      // alpha chunk size
     58   size_t compressed_size;      // VP8/VP8L compressed data size
     59   size_t riff_size;            // size of the riff payload (or 0 if absent)
     60   int is_lossless;             // true if a VP8L chunk is present
     61 } WebPHeaderStructure;
     62 
     63 // Skips over all valid chunks prior to the first VP8/VP8L frame header.
     64 // Returns VP8_STATUS_OK on success,
     65 //         VP8_STATUS_BITSTREAM_ERROR if an invalid header/chunk is found, and
     66 //         VP8_STATUS_NOT_ENOUGH_DATA if case of insufficient data.
     67 // In 'headers', compressed_size, offset, alpha_data, alpha_size and lossless
     68 // fields are updated appropriately upon success.
     69 VP8StatusCode WebPParseHeaders(WebPHeaderStructure* const headers);
     70 
     71 //------------------------------------------------------------------------------
     72 // Misc utils
     73 
     74 // Initializes VP8Io with custom setup, io and teardown functions. The default
     75 // hooks will use the supplied 'params' as io->opaque handle.
     76 void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io);
     77 
     78 // Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers
     79 // to the *compressed* format, not the output one.
     80 int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
     81                           VP8Io* const io, WEBP_CSP_MODE src_colorspace);
     82 
     83 //------------------------------------------------------------------------------
     84 // Internal functions regarding WebPDecBuffer memory (in buffer.c).
     85 // Don't really need to be externally visible for now.
     86 
     87 // Prepare 'buffer' with the requested initial dimensions width/height.
     88 // If no external storage is supplied, initializes buffer by allocating output
     89 // memory and setting up the stride information. Validate the parameters. Return
     90 // an error code in case of problem (no memory, or invalid stride / size /
     91 // dimension / etc.). If *options is not NULL, also verify that the options'
     92 // parameters are valid and apply them to the width/height dimensions of the
     93 // output buffer. This takes cropping / scaling / rotation into account.
     94 VP8StatusCode WebPAllocateDecBuffer(int width, int height,
     95                                     const WebPDecoderOptions* const options,
     96                                     WebPDecBuffer* const buffer);
     97 
     98 // Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the
     99 // memory (still held by 'src').
    100 void WebPCopyDecBuffer(const WebPDecBuffer* const src,
    101                        WebPDecBuffer* const dst);
    102 
    103 // Copy and transfer ownership from src to dst (beware of parameter order!)
    104 void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst);
    105 
    106 
    107 
    108 //------------------------------------------------------------------------------
    109 
    110 #if defined(__cplusplus) || defined(c_plusplus)
    111 }    // extern "C"
    112 #endif
    113 
    114 #endif  /* WEBP_DEC_WEBPI_H_ */
    115