third_party/libwebp/dec/webpi.h

   1 // Copyright 2011 Google Inc. All Rights Reserved.
   2 //
   3 // Use of this source code is governed by a BSD-style license
   4 // that can be found in the COPYING file in the root of the source
   5 // tree. An additional intellectual property rights grant can be found
   6 // in the file PATENTS. All contributing project authors may
   7 // be found in the AUTHORS file in the root of the source tree.
   8 // -----------------------------------------------------------------------------
   9 //
  10 // Internal header: WebP decoding parameters and custom IO on buffer
  11 //
  12 // Author: somnath@google.com (Somnath Banerjee)
  13
  14 #ifndef WEBP_DEC_WEBPI_H_
  15 #define WEBP_DEC_WEBPI_H_
  16
  17 #ifdef __cplusplus
  18 extern "C" {
  19 #endif
  20
  21 #include "../utils/rescaler.h"
  22 #include "./decode_vp8.h"
  23
  24 //------------------------------------------------------------------------------
  25 // WebPDecParams: Decoding output parameters. Transient internal object.
  26
  27 typedef struct WebPDecParams WebPDecParams;
  28 typedef int (*OutputFunc)(const VP8Io* const io, WebPDecParams* const p);
  29 typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos);
  30
  31 struct WebPDecParams {
  32   WebPDecBuffer* output;             // output buffer.
  33   uint8_t* tmp_y, *tmp_u, *tmp_v;    // cache for the fancy upsampler
  34                                      // or used for tmp rescaling
  35
  36   int last_y;                 // coordinate of the line that was last output
  37   const WebPDecoderOptions* options;  // if not NULL, use alt decoding features
  38   // rescalers
  39   WebPRescaler scaler_y, scaler_u, scaler_v, scaler_a;
  40   void* memory;                  // overall scratch memory for the output work.
  41
  42   OutputFunc emit;               // output RGB or YUV samples
  43   OutputFunc emit_alpha;         // output alpha channel
  44   OutputRowFunc emit_alpha_row;  // output one line of rescaled alpha values
  45 };
  46
  47 // Should be called first, before any use of the WebPDecParams object.
  48 void WebPResetDecParams(WebPDecParams* const params);
  49
  50 //------------------------------------------------------------------------------
  51 // Header parsing helpers
  52
  53 // Structure storing a description of the RIFF headers.
  54 typedef struct {
  55   const uint8_t* data;         // input buffer
  56   size_t data_size;            // input buffer size
  57   int have_all_data;           // true if all data is known to be available
  58   size_t offset;               // offset to main data chunk (VP8 or VP8L)
  59   const uint8_t* alpha_data;   // points to alpha chunk (if present)
  60   size_t alpha_data_size;      // alpha chunk size
  61   size_t compressed_size;      // VP8/VP8L compressed data size
  62   size_t riff_size;            // size of the riff payload (or 0 if absent)
  63   int is_lossless;             // true if a VP8L chunk is present
  64 } WebPHeaderStructure;
  65
  66 // Skips over all valid chunks prior to the first VP8/VP8L frame header.
  67 // Returns: VP8_STATUS_OK, VP8_STATUS_BITSTREAM_ERROR (invalid header/chunk),
  68 // VP8_STATUS_NOT_ENOUGH_DATA (partial input) or VP8_STATUS_UNSUPPORTED_FEATURE
  69 // in the case of non-decodable features (animation for instance).
  70 // In 'headers', compressed_size, offset, alpha_data, alpha_size, and lossless
  71 // fields are updated appropriately upon success.
  72 VP8StatusCode WebPParseHeaders(WebPHeaderStructure* const headers);
  73
  74 //------------------------------------------------------------------------------
  75 // Misc utils
  76
  77 // Initializes VP8Io with custom setup, io and teardown functions. The default
  78 // hooks will use the supplied 'params' as io->opaque handle.
  79 void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io);
  80
  81 // Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers
  82 // to the *compressed* format, not the output one.
  83 int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
  84                           VP8Io* const io, WEBP_CSP_MODE src_colorspace);
  85
  86 //------------------------------------------------------------------------------
  87 // Internal functions regarding WebPDecBuffer memory (in buffer.c).
  88 // Don't really need to be externally visible for now.
  89
  90 // Prepare 'buffer' with the requested initial dimensions width/height.
  91 // If no external storage is supplied, initializes buffer by allocating output
  92 // memory and setting up the stride information. Validate the parameters. Return
  93 // an error code in case of problem (no memory, or invalid stride / size /
  94 // dimension / etc.). If *options is not NULL, also verify that the options'
  95 // parameters are valid and apply them to the width/height dimensions of the
  96 // output buffer. This takes cropping / scaling / rotation into account.
  97 // Also incorporates the options->flip flag to flip the buffer parameters if
  98 // needed.
  99 VP8StatusCode WebPAllocateDecBuffer(int width, int height,
 100                                     const WebPDecoderOptions* const options,
 101                                     WebPDecBuffer* const buffer);
 102
 103 // Flip buffer vertically by negating the various strides.
 104 VP8StatusCode WebPFlipBuffer(WebPDecBuffer* const buffer);
 105
 106 // Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the
 107 // memory (still held by 'src').
 108 void WebPCopyDecBuffer(const WebPDecBuffer* const src,
 109                        WebPDecBuffer* const dst);
 110
 111 // Copy and transfer ownership from src to dst (beware of parameter order!)
 112 void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst);
 113
 114 //------------------------------------------------------------------------------
 115
 116 #ifdef __cplusplus
 117 }    // extern "C"
 118 #endif
 119
 120 #endif  /* WEBP_DEC_WEBPI_H_ */