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// Copyright 2010 Google Inc. All Rights Reserved.
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
// Low-level API for VP8 decoder
// Author: Skal (
#include "../webp/decode.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
// Lower-level API
// These functions provide fine-grained control of the decoding process.
// The call flow should resemble:
// VP8Io io;
// VP8InitIo(&io);
// = data;
// io.data_size = size;
// /* customize io's functions (setup()/put()/teardown()) if needed. */
// VP8Decoder* dec = VP8New();
// bool ok = VP8Decode(dec);
// if (!ok) printf("Error: %s\n", VP8StatusMessage(dec));
// VP8Delete(dec);
// return ok;
// Input / Output
typedef struct VP8Io VP8Io;
typedef int (*VP8IoPutHook)(const VP8Io* io);
typedef int (*VP8IoSetupHook)(VP8Io* io);
typedef void (*VP8IoTeardownHook)(const VP8Io* io);
struct VP8Io {
// set by VP8GetHeaders()
int width, height; // picture dimensions, in pixels (invariable).
// These are the original, uncropped dimensions.
// The actual area passed to put() is stored
// in mb_w / mb_h fields.
// set before calling put()
int mb_y; // position of the current rows (in pixels)
int mb_w; // number of columns in the sample
int mb_h; // number of rows in the sample
const uint8_t* y, *u, *v; // rows to copy (in yuv420 format)
int y_stride; // row stride for luma
int uv_stride; // row stride for chroma
void* opaque; // user data
// called when fresh samples are available. Currently, samples are in
// YUV420 format, and can be up to width x 24 in size (depending on the
// in-loop filtering level, e.g.). Should return false in case of error
// or abort request. The actual size of the area to update is mb_w x mb_h
// in size, taking cropping into account.
VP8IoPutHook put;
// called just before starting to decode the blocks.
// Must return false in case of setup error, true otherwise. If false is
// returned, teardown() will NOT be called. But if the setup succeeded
// and true is returned, then teardown() will always be called afterward.
VP8IoSetupHook setup;
// Called just after block decoding is finished (or when an error occurred
// during put()). Is NOT called if setup() failed.
VP8IoTeardownHook teardown;
// this is a recommendation for the user-side yuv->rgb converter. This flag
// is set when calling setup() hook and can be overwritten by it. It then
// can be taken into consideration during the put() method.
int fancy_upsampling;
// Input buffer.
size_t data_size;
const uint8_t* data;
// If true, in-loop filtering will not be performed even if present in the
// bitstream. Switching off filtering may speed up decoding at the expense
// of more visible blocking. Note that output will also be non-compliant
// with the VP8 specifications.
int bypass_filtering;
// Cropping parameters.
int use_cropping;
int crop_left, crop_right, crop_top, crop_bottom;
// Scaling parameters.
int use_scaling;
int scaled_width, scaled_height;
// If non NULL, pointer to the alpha data (if present) corresponding to the
// start of the current row (That is: it is pre-offset by mb_y and takes
// cropping into account).
const uint8_t* a;
// Internal, version-checked, entry point
int VP8InitIoInternal(VP8Io* const, int);
// Set the custom IO function pointers and user-data. The setter for IO hooks
// should be called before initiating incremental decoding. Returns true if
// WebPIDecoder object is successfully modified, false otherwise.
int WebPISetIOHooks(WebPIDecoder* const idec,
VP8IoPutHook put,
VP8IoSetupHook setup,
VP8IoTeardownHook teardown,
void* user_data);
// Main decoding object. This is an opaque structure.
typedef struct VP8Decoder VP8Decoder;
// Create a new decoder object.
VP8Decoder* VP8New(void);
// Must be called to make sure 'io' is initialized properly.
// Returns false in case of version mismatch. Upon such failure, no other
// decoding function should be called (VP8Decode, VP8GetHeaders, ...)
static WEBP_INLINE int VP8InitIo(VP8Io* const io) {
return VP8InitIoInternal(io, WEBP_DECODER_ABI_VERSION);
// Start decoding a new picture. Returns true if ok.
int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io);
// Decode a picture. Will call VP8GetHeaders() if it wasn't done already.
// Returns false in case of error.
int VP8Decode(VP8Decoder* const dec, VP8Io* const io);
// Return current status of the decoder:
VP8StatusCode VP8Status(VP8Decoder* const dec);
// return readable string corresponding to the last status.
const char* VP8StatusMessage(VP8Decoder* const dec);
// Resets the decoder in its initial state, reclaiming memory.
// Not a mandatory call between calls to VP8Decode().
void VP8Clear(VP8Decoder* const dec);
// Destroy the decoder object.
void VP8Delete(VP8Decoder* const dec);
// Miscellaneous VP8/VP8L bitstream probing functions.
// Returns true if the next 3 bytes in data contain the VP8 signature.
WEBP_EXTERN(int) VP8CheckSignature(const uint8_t* const data, size_t data_size);
// Validates the VP8 data-header and retrieves basic header information viz
// width and height. Returns 0 in case of formatting error. *width/*height
// can be passed NULL.
WEBP_EXTERN(int) VP8GetInfo(
const uint8_t* data,
size_t data_size, // data available so far
size_t chunk_size, // total data size expected in the chunk
int* const width, int* const height);
// Returns true if the next byte(s) in data is a VP8L signature.
WEBP_EXTERN(int) VP8LCheckSignature(const uint8_t* const data, size_t size);
// Validates the VP8L data-header and retrieves basic header information viz
// width, height and alpha. Returns 0 in case of formatting error.
// width/height/has_alpha can be passed NULL.
const uint8_t* data, size_t data_size, // data available so far
int* const width, int* const height, int* const has_alpha);
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif /* WEBP_WEBP_DECODE_VP8_H_ */