1 // Copyright 2012 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 // Lossless decoder: internal header.
11 //
12 // Author: Skal (pascal.massimino@gmail.com)
13 //         Vikas Arora(vikaas.arora@gmail.com)
14 
15 #ifndef WEBP_DEC_VP8LI_H_
16 #define WEBP_DEC_VP8LI_H_
17 
18 #include <string.h>     // for memcpy()
19 #include "./webpi.h"
20 #include "../utils/bit_reader.h"
21 #include "../utils/color_cache.h"
22 #include "../utils/huffman.h"
23 
24 #ifdef __cplusplus
25 extern "C" {
26 #endif
27 
28 typedef enum {
29   READ_DATA = 0,
30   READ_HDR = 1,
31   READ_DIM = 2
32 } VP8LDecodeState;
33 
34 typedef struct VP8LTransform VP8LTransform;
35 struct VP8LTransform {
36   VP8LImageTransformType type_;   // transform type.
37   int                    bits_;   // subsampling bits defining transform window.
38   int                    xsize_;  // transform window X index.
39   int                    ysize_;  // transform window Y index.
40   uint32_t              *data_;   // transform data.
41 };
42 
43 typedef struct {
44   int             color_cache_size_;
45   VP8LColorCache  color_cache_;
46 
47   int             huffman_mask_;
48   int             huffman_subsample_bits_;
49   int             huffman_xsize_;
50   uint32_t       *huffman_image_;
51   int             num_htree_groups_;
52   HTreeGroup     *htree_groups_;
53 } VP8LMetadata;
54 
55 typedef struct VP8LDecoder VP8LDecoder;
56 struct VP8LDecoder {
57   VP8StatusCode    status_;
58   VP8LDecodeState  action_;
59   VP8LDecodeState  state_;
60   VP8Io           *io_;
61 
62   const WebPDecBuffer *output_;    // shortcut to io->opaque->output
63 
64   uint32_t        *pixels_;        // Internal data: either uint8_t* for alpha
65                                    // or uint32_t* for BGRA.
66   uint32_t        *argb_cache_;    // Scratch buffer for temporary BGRA storage.
67 
68   VP8LBitReader    br_;
69 
70   int              width_;
71   int              height_;
72   int              last_row_;      // last input row decoded so far.
73   int              last_pixel_;    // last pixel decoded so far. However, it may
74                                    // not be transformed, scaled and
75                                    // color-converted yet.
76   int              last_out_row_;  // last row output so far.
77 
78   VP8LMetadata     hdr_;
79 
80   int              next_transform_;
81   VP8LTransform    transforms_[NUM_TRANSFORMS];
82   // or'd bitset storing the transforms types.
83   uint32_t         transforms_seen_;
84 
85   uint8_t         *rescaler_memory;  // Working memory for rescaling work.
86   WebPRescaler    *rescaler;         // Common rescaler for all channels.
87 };
88 
89 //------------------------------------------------------------------------------
90 // internal functions. Not public.
91 
92 struct ALPHDecoder;  // Defined in dec/alphai.h.
93 
94 // in vp8l.c
95 
96 // Decodes image header for alpha data stored using lossless compression.
97 // Returns false in case of error.
98 int VP8LDecodeAlphaHeader(struct ALPHDecoder* const alph_dec,
99                           const uint8_t* const data, size_t data_size,
100                           uint8_t* const output);
101 
102 // Decodes *at least* 'last_row' rows of alpha. If some of the initial rows are
103 // already decoded in previous call(s), it will resume decoding from where it
104 // was paused.
105 // Returns false in case of bitstream error.
106 int VP8LDecodeAlphaImageStream(struct ALPHDecoder* const alph_dec,
107                                int last_row);
108 
109 // Allocates and initialize a new lossless decoder instance.
110 VP8LDecoder* VP8LNew(void);
111 
112 // Decodes the image header. Returns false in case of error.
113 int VP8LDecodeHeader(VP8LDecoder* const dec, VP8Io* const io);
114 
115 // Decodes an image. It's required to decode the lossless header before calling
116 // this function. Returns false in case of error, with updated dec->status_.
117 int VP8LDecodeImage(VP8LDecoder* const dec);
118 
119 // Resets the decoder in its initial state, reclaiming memory.
120 // Preserves the dec->status_ value.
121 void VP8LClear(VP8LDecoder* const dec);
122 
123 // Clears and deallocate a lossless decoder instance.
124 void VP8LDelete(VP8LDecoder* const dec);
125 
126 //------------------------------------------------------------------------------
127 
128 #ifdef __cplusplus
129 }    // extern "C"
130 #endif
131 
132 #endif  /* WEBP_DEC_VP8LI_H_ */
133