third_party/libwebp/dec/decode_vp8.h

   1 // Copyright 2010 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 //  Low-level API for VP8 decoder
  11 //
  12 // Author: Skal (pascal.massimino@gmail.com)
  13
  14 #ifndef WEBP_WEBP_DECODE_VP8_H_
  15 #define WEBP_WEBP_DECODE_VP8_H_
  16
  17 #include "../webp/decode.h"
  18
  19 #if defined(__cplusplus) || defined(c_plusplus)
  20 extern "C" {
  21 #endif
  22
  23 //------------------------------------------------------------------------------
  24 // Lower-level API
  25 //
  26 // These functions provide fine-grained control of the decoding process.
  27 // The call flow should resemble:
  28 //
  29 //   VP8Io io;
  30 //   VP8InitIo(&io);
  31 //   io.data = data;
  32 //   io.data_size = size;
  33 //   /* customize io's functions (setup()/put()/teardown()) if needed. */
  34 //
  35 //   VP8Decoder* dec = VP8New();
  36 //   bool ok = VP8Decode(dec);
  37 //   if (!ok) printf("Error: %s\n", VP8StatusMessage(dec));
  38 //   VP8Delete(dec);
  39 //   return ok;
  40
  41 // Input / Output
  42 typedef struct VP8Io VP8Io;
  43 typedef int (*VP8IoPutHook)(const VP8Io* io);
  44 typedef int (*VP8IoSetupHook)(VP8Io* io);
  45 typedef void (*VP8IoTeardownHook)(const VP8Io* io);
  46
  47 struct VP8Io {
  48   // set by VP8GetHeaders()
  49   int width, height;         // picture dimensions, in pixels (invariable).
  50                              // These are the original, uncropped dimensions.
  51                              // The actual area passed to put() is stored
  52                              // in mb_w / mb_h fields.
  53
  54   // set before calling put()
  55   int mb_y;                  // position of the current rows (in pixels)
  56   int mb_w;                  // number of columns in the sample
  57   int mb_h;                  // number of rows in the sample
  58   const uint8_t* y, *u, *v;  // rows to copy (in yuv420 format)
  59   int y_stride;              // row stride for luma
  60   int uv_stride;             // row stride for chroma
  61
  62   void* opaque;              // user data
  63
  64   // called when fresh samples are available. Currently, samples are in
  65   // YUV420 format, and can be up to width x 24 in size (depending on the
  66   // in-loop filtering level, e.g.). Should return false in case of error
  67   // or abort request. The actual size of the area to update is mb_w x mb_h
  68   // in size, taking cropping into account.
  69   VP8IoPutHook put;
  70
  71   // called just before starting to decode the blocks.
  72   // Must return false in case of setup error, true otherwise. If false is
  73   // returned, teardown() will NOT be called. But if the setup succeeded
  74   // and true is returned, then teardown() will always be called afterward.
  75   VP8IoSetupHook setup;
  76
  77   // Called just after block decoding is finished (or when an error occurred
  78   // during put()). Is NOT called if setup() failed.
  79   VP8IoTeardownHook teardown;
  80
  81   // this is a recommendation for the user-side yuv->rgb converter. This flag
  82   // is set when calling setup() hook and can be overwritten by it. It then
  83   // can be taken into consideration during the put() method.
  84   int fancy_upsampling;
  85
  86   // Input buffer.
  87   size_t data_size;
  88   const uint8_t* data;
  89
  90   // If true, in-loop filtering will not be performed even if present in the
  91   // bitstream. Switching off filtering may speed up decoding at the expense
  92   // of more visible blocking. Note that output will also be non-compliant
  93   // with the VP8 specifications.
  94   int bypass_filtering;
  95
  96   // Cropping parameters.
  97   int use_cropping;
  98   int crop_left, crop_right, crop_top, crop_bottom;
  99
 100   // Scaling parameters.
 101   int use_scaling;
 102   int scaled_width, scaled_height;
 103
 104   // If non NULL, pointer to the alpha data (if present) corresponding to the
 105   // start of the current row (That is: it is pre-offset by mb_y and takes
 106   // cropping into account).
 107   const uint8_t* a;
 108 };
 109
 110 // Internal, version-checked, entry point
 111 int VP8InitIoInternal(VP8Io* const, int);
 112
 113 // Set the custom IO function pointers and user-data. The setter for IO hooks
 114 // should be called before initiating incremental decoding. Returns true if
 115 // WebPIDecoder object is successfully modified, false otherwise.
 116 int WebPISetIOHooks(WebPIDecoder* const idec,
 117                     VP8IoPutHook put,
 118                     VP8IoSetupHook setup,
 119                     VP8IoTeardownHook teardown,
 120                     void* user_data);
 121
 122 // Main decoding object. This is an opaque structure.
 123 typedef struct VP8Decoder VP8Decoder;
 124
 125 // Create a new decoder object.
 126 VP8Decoder* VP8New(void);
 127
 128 // Must be called to make sure 'io' is initialized properly.
 129 // Returns false in case of version mismatch. Upon such failure, no other
 130 // decoding function should be called (VP8Decode, VP8GetHeaders, ...)
 131 static WEBP_INLINE int VP8InitIo(VP8Io* const io) {
 132   return VP8InitIoInternal(io, WEBP_DECODER_ABI_VERSION);
 133 }
 134
 135 // Start decoding a new picture. Returns true if ok.
 136 int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io);
 137
 138 // Decode a picture. Will call VP8GetHeaders() if it wasn't done already.
 139 // Returns false in case of error.
 140 int VP8Decode(VP8Decoder* const dec, VP8Io* const io);
 141
 142 // Return current status of the decoder:
 143 VP8StatusCode VP8Status(VP8Decoder* const dec);
 144
 145 // return readable string corresponding to the last status.
 146 const char* VP8StatusMessage(VP8Decoder* const dec);
 147
 148 // Resets the decoder in its initial state, reclaiming memory.
 149 // Not a mandatory call between calls to VP8Decode().
 150 void VP8Clear(VP8Decoder* const dec);
 151
 152 // Destroy the decoder object.
 153 void VP8Delete(VP8Decoder* const dec);
 154
 155 //------------------------------------------------------------------------------
 156 // Miscellaneous VP8/VP8L bitstream probing functions.
 157
 158 // Returns true if the next 3 bytes in data contain the VP8 signature.
 159 WEBP_EXTERN(int) VP8CheckSignature(const uint8_t* const data, size_t data_size);
 160
 161 // Validates the VP8 data-header and retrieves basic header information viz
 162 // width and height. Returns 0 in case of formatting error. *width/*height
 163 // can be passed NULL.
 164 WEBP_EXTERN(int) VP8GetInfo(
 165     const uint8_t* data,
 166     size_t data_size,    // data available so far
 167     size_t chunk_size,   // total data size expected in the chunk
 168     int* const width, int* const height);
 169
 170 // Returns true if the next byte(s) in data is a VP8L signature.
 171 WEBP_EXTERN(int) VP8LCheckSignature(const uint8_t* const data, size_t size);
 172
 173 // Validates the VP8L data-header and retrieves basic header information viz
 174 // width, height and alpha. Returns 0 in case of formatting error.
 175 // width/height/has_alpha can be passed NULL.
 176 WEBP_EXTERN(int) VP8LGetInfo(
 177     const uint8_t* data, size_t data_size,  // data available so far
 178     int* const width, int* const height, int* const has_alpha);
 179
 180 #if defined(__cplusplus) || defined(c_plusplus)
 181 }    // extern "C"
 182 #endif
 183
 184 #endif  /* WEBP_WEBP_DECODE_VP8_H_ */