185 lines
6.8 KiB
C++
185 lines
6.8 KiB
C++
// Copyright 2010 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Low-level API for VP8 decoder
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//
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// Author: Skal (pascal.massimino@gmail.com)
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#ifndef WEBP_WEBP_DECODE_VP8_H_
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#define WEBP_WEBP_DECODE_VP8_H_
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#include "webp/decode.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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//------------------------------------------------------------------------------
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// Lower-level API
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//
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// These functions provide fine-grained control of the decoding process.
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// The call flow should resemble:
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//
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// VP8Io io;
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// VP8InitIo(&io);
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// io.data = data;
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// io.data_size = size;
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// /* customize io's functions (setup()/put()/teardown()) if needed. */
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//
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// VP8Decoder* dec = VP8New();
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// bool ok = VP8Decode(dec);
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// if (!ok) printf("Error: %s\n", VP8StatusMessage(dec));
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// VP8Delete(dec);
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// return ok;
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// Input / Output
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typedef struct VP8Io VP8Io;
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typedef int (*VP8IoPutHook)(const VP8Io* io);
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typedef int (*VP8IoSetupHook)(VP8Io* io);
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typedef void (*VP8IoTeardownHook)(const VP8Io* io);
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struct VP8Io {
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// set by VP8GetHeaders()
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int width, height; // picture dimensions, in pixels (invariable).
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// These are the original, uncropped dimensions.
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// The actual area passed to put() is stored
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// in mb_w / mb_h fields.
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// set before calling put()
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int mb_y; // position of the current rows (in pixels)
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int mb_w; // number of columns in the sample
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int mb_h; // number of rows in the sample
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const uint8_t* y, *u, *v; // rows to copy (in yuv420 format)
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int y_stride; // row stride for luma
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int uv_stride; // row stride for chroma
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void* opaque; // user data
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// called when fresh samples are available. Currently, samples are in
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// YUV420 format, and can be up to width x 24 in size (depending on the
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// in-loop filtering level, e.g.). Should return false in case of error
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// or abort request. The actual size of the area to update is mb_w x mb_h
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// in size, taking cropping into account.
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VP8IoPutHook put;
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// called just before starting to decode the blocks.
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// Must return false in case of setup error, true otherwise. If false is
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// returned, teardown() will NOT be called. But if the setup succeeded
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// and true is returned, then teardown() will always be called afterward.
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VP8IoSetupHook setup;
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// Called just after block decoding is finished (or when an error occurred
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// during put()). Is NOT called if setup() failed.
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VP8IoTeardownHook teardown;
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// this is a recommendation for the user-side yuv->rgb converter. This flag
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// is set when calling setup() hook and can be overwritten by it. It then
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// can be taken into consideration during the put() method.
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int fancy_upsampling;
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// Input buffer.
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size_t data_size;
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const uint8_t* data;
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// If true, in-loop filtering will not be performed even if present in the
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// bitstream. Switching off filtering may speed up decoding at the expense
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// of more visible blocking. Note that output will also be non-compliant
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// with the VP8 specifications.
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int bypass_filtering;
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// Cropping parameters.
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int use_cropping;
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int crop_left, crop_right, crop_top, crop_bottom;
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// Scaling parameters.
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int use_scaling;
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int scaled_width, scaled_height;
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// If non NULL, pointer to the alpha data (if present) corresponding to the
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// start of the current row (That is: it is pre-offset by mb_y and takes
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// cropping into account).
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const uint8_t* a;
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};
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// Internal, version-checked, entry point
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int VP8InitIoInternal(VP8Io* const, int);
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// Set the custom IO function pointers and user-data. The setter for IO hooks
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// should be called before initiating incremental decoding. Returns true if
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// WebPIDecoder object is successfully modified, false otherwise.
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int WebPISetIOHooks(WebPIDecoder* const idec,
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VP8IoPutHook put,
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VP8IoSetupHook setup,
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VP8IoTeardownHook teardown,
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void* user_data);
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// Main decoding object. This is an opaque structure.
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typedef struct VP8Decoder VP8Decoder;
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// Create a new decoder object.
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VP8Decoder* VP8New(void);
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// Must be called to make sure 'io' is initialized properly.
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// Returns false in case of version mismatch. Upon such failure, no other
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// decoding function should be called (VP8Decode, VP8GetHeaders, ...)
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static WEBP_INLINE int VP8InitIo(VP8Io* const io) {
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return VP8InitIoInternal(io, WEBP_DECODER_ABI_VERSION);
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}
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// Decode the VP8 frame header. Returns true if ok.
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// Note: 'io->data' must be pointing to the start of the VP8 frame header.
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int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io);
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// Decode a picture. Will call VP8GetHeaders() if it wasn't done already.
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// Returns false in case of error.
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int VP8Decode(VP8Decoder* const dec, VP8Io* const io);
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// Return current status of the decoder:
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VP8StatusCode VP8Status(VP8Decoder* const dec);
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// return readable string corresponding to the last status.
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const char* VP8StatusMessage(VP8Decoder* const dec);
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// Resets the decoder in its initial state, reclaiming memory.
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// Not a mandatory call between calls to VP8Decode().
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void VP8Clear(VP8Decoder* const dec);
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// Destroy the decoder object.
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void VP8Delete(VP8Decoder* const dec);
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//------------------------------------------------------------------------------
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// Miscellaneous VP8/VP8L bitstream probing functions.
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// Returns true if the next 3 bytes in data contain the VP8 signature.
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WEBP_EXTERN(int) VP8CheckSignature(const uint8_t* const data, size_t data_size);
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// Validates the VP8 data-header and retrieves basic header information viz
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// width and height. Returns 0 in case of formatting error. *width/*height
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// can be passed NULL.
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WEBP_EXTERN(int) VP8GetInfo(
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const uint8_t* data,
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size_t data_size, // data available so far
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size_t chunk_size, // total data size expected in the chunk
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int* const width, int* const height);
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// Returns true if the next byte(s) in data is a VP8L signature.
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WEBP_EXTERN(int) VP8LCheckSignature(const uint8_t* const data, size_t size);
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// Validates the VP8L data-header and retrieves basic header information viz
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// width, height and alpha. Returns 0 in case of formatting error.
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// width/height/has_alpha can be passed NULL.
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WEBP_EXTERN(int) VP8LGetInfo(
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const uint8_t* data, size_t data_size, // data available so far
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int* const width, int* const height, int* const has_alpha);
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#ifdef __cplusplus
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} // extern "C"
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#endif
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#endif /* WEBP_WEBP_DECODE_VP8_H_ */
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