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1 // Copyright 2010 Google Inc. | |
2 // | |
3 // This code is licensed under the same terms as WebM: | |
4 // Software License Agreement: http://www.webmproject.org/license/software/ | |
5 // Additional IP Rights Grant: http://www.webmproject.org/license/additional/ | |
6 // ----------------------------------------------------------------------------- | |
7 // | |
8 // Low-level API for VP8 decoder | |
9 // | |
10 // Author: Skal (pascal.massimino@gmail.com) | |
11 | |
12 #ifndef WEBP_WEBP_DECODE_VP8_H_ | |
13 #define WEBP_WEBP_DECODE_VP8_H_ | |
14 | |
15 #include "./decode.h" | |
16 | |
17 #if defined(__cplusplus) || defined(c_plusplus) | |
18 extern "C" { | |
19 #endif | |
20 | |
21 //------------------------------------------------------------------------------ | |
22 // Lower-level API | |
23 // | |
24 // These functions provide fine-grained control of the decoding process. | |
25 // The call flow should resemble: | |
26 // | |
27 // VP8Io io; | |
28 // VP8InitIo(&io); | |
29 // io.data = data; | |
30 // io.data_size = size; | |
31 // /* customize io's functions (setup()/put()/teardown()) if needed. */ | |
32 // | |
33 // VP8Decoder* dec = VP8New(); | |
34 // bool ok = VP8Decode(dec); | |
35 // if (!ok) printf("Error: %s\n", VP8StatusMessage(dec)); | |
36 // VP8Delete(dec); | |
37 // return ok; | |
38 | |
39 // Input / Output | |
40 typedef struct VP8Io VP8Io; | |
41 typedef int (*VP8IoPutHook)(const VP8Io* io); | |
42 typedef int (*VP8IoSetupHook)(VP8Io* io); | |
43 typedef void (*VP8IoTeardownHook)(const VP8Io* io); | |
44 | |
45 struct VP8Io { | |
46 // set by VP8GetHeaders() | |
47 int width, height; // picture dimensions, in pixels (invariable). | |
48 // These are the original, uncropped dimensions. | |
49 // The actual area passed to put() is stored | |
50 // in mb_w / mb_h fields. | |
51 | |
52 // set before calling put() | |
53 int mb_y; // position of the current rows (in pixels) | |
54 int mb_w; // number of columns in the sample | |
55 int mb_h; // number of rows in the sample | |
56 const uint8_t* y, *u, *v; // rows to copy (in yuv420 format) | |
57 int y_stride; // row stride for luma | |
58 int uv_stride; // row stride for chroma | |
59 | |
60 void* opaque; // user data | |
61 | |
62 // called when fresh samples are available. Currently, samples are in | |
63 // YUV420 format, and can be up to width x 24 in size (depending on the | |
64 // in-loop filtering level, e.g.). Should return false in case of error | |
65 // or abort request. The actual size of the area to update is mb_w x mb_h | |
66 // in size, taking cropping into account. | |
67 VP8IoPutHook put; | |
68 | |
69 // called just before starting to decode the blocks. | |
70 // Must return false in case of setup error, true otherwise. If false is | |
71 // returned, teardown() will NOT be called. But if the setup succeeded | |
72 // and true is returned, then teardown() will always be called afterward. | |
73 VP8IoSetupHook setup; | |
74 | |
75 // Called just after block decoding is finished (or when an error occurred | |
76 // during put()). Is NOT called if setup() failed. | |
77 VP8IoTeardownHook teardown; | |
78 | |
79 // this is a recommendation for the user-side yuv->rgb converter. This flag | |
80 // is set when calling setup() hook and can be overwritten by it. It then | |
81 // can be taken into consideration during the put() method. | |
82 int fancy_upsampling; | |
83 | |
84 // Input buffer. | |
85 uint32_t data_size; | |
86 const uint8_t* data; | |
87 | |
88 // If true, in-loop filtering will not be performed even if present in the | |
89 // bitstream. Switching off filtering may speed up decoding at the expense | |
90 // of more visible blocking. Note that output will also be non-compliant | |
91 // with the VP8 specifications. | |
92 int bypass_filtering; | |
93 | |
94 // Cropping parameters. | |
95 int use_cropping; | |
96 int crop_left, crop_right, crop_top, crop_bottom; | |
97 | |
98 // Scaling parameters. | |
99 int use_scaling; | |
100 int scaled_width, scaled_height; | |
101 | |
102 // pointer to the alpha data (if present) corresponding to the rows | |
103 const uint8_t* a; | |
104 }; | |
105 | |
106 // Internal, version-checked, entry point | |
107 WEBP_EXTERN(int) VP8InitIoInternal(VP8Io* const, int); | |
108 | |
109 // Set the custom IO function pointers and user-data. The setter for IO hooks | |
110 // should be called before initiating incremental decoding. Returns true if | |
111 // WebPIDecoder object is successfully modified, false otherwise. | |
112 WEBP_EXTERN(int) WebPISetIOHooks(WebPIDecoder* const idec, | |
113 VP8IoPutHook put, | |
114 VP8IoSetupHook setup, | |
115 VP8IoTeardownHook teardown, | |
116 void* user_data); | |
117 | |
118 // Main decoding object. This is an opaque structure. | |
119 typedef struct VP8Decoder VP8Decoder; | |
120 | |
121 // Create a new decoder object. | |
122 WEBP_EXTERN(VP8Decoder*) VP8New(void); | |
123 | |
124 // Must be called to make sure 'io' is initialized properly. | |
125 // Returns false in case of version mismatch. Upon such failure, no other | |
126 // decoding function should be called (VP8Decode, VP8GetHeaders, ...) | |
127 static inline int VP8InitIo(VP8Io* const io) { | |
128 return VP8InitIoInternal(io, WEBP_DECODER_ABI_VERSION); | |
129 } | |
130 | |
131 // Start decoding a new picture. Returns true if ok. | |
132 WEBP_EXTERN(int) VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io); | |
133 | |
134 // Decode a picture. Will call VP8GetHeaders() if it wasn't done already. | |
135 // Returns false in case of error. | |
136 WEBP_EXTERN(int) VP8Decode(VP8Decoder* const dec, VP8Io* const io); | |
137 | |
138 // Return current status of the decoder: | |
139 WEBP_EXTERN(VP8StatusCode) VP8Status(VP8Decoder* const dec); | |
140 | |
141 // return readable string corresponding to the last status. | |
142 WEBP_EXTERN(const char*) VP8StatusMessage(VP8Decoder* const dec); | |
143 | |
144 // Resets the decoder in its initial state, reclaiming memory. | |
145 // Not a mandatory call between calls to VP8Decode(). | |
146 WEBP_EXTERN(void) VP8Clear(VP8Decoder* const dec); | |
147 | |
148 // Destroy the decoder object. | |
149 WEBP_EXTERN(void) VP8Delete(VP8Decoder* const dec); | |
150 | |
151 //------------------------------------------------------------------------------ | |
152 | |
153 #if defined(__cplusplus) || defined(c_plusplus) | |
154 } // extern "C" | |
155 #endif | |
156 | |
157 #endif /* WEBP_WEBP_DECODE_VP8_H_ */ | |
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