1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
// 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 (pascal.massimino@gmail.com)
#ifndef WEBP_WEBP_DECODE_VP8_H_
#define WEBP_WEBP_DECODE_VP8_H_
#include "../webp/decode.h"
#ifdef __cplusplus
extern "C" {
#endif
//------------------------------------------------------------------------------
// Lower-level API
//
// These functions provide fine-grained control of the decoding process.
// The call flow should resemble:
//
// VP8Io io;
// VP8InitIo(&io);
// io.data = 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);
}
// Decode the VP8 frame header. Returns true if ok.
// Note: 'io->data' must be pointing to the start of the VP8 frame header.
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.
WEBP_EXTERN(int) VP8LGetInfo(
const uint8_t* data, size_t data_size, // data available so far
int* const width, int* const height, int* const has_alpha);
#ifdef __cplusplus
} // extern "C"
#endif
#endif /* WEBP_WEBP_DECODE_VP8_H_ */
|