1 // Copyright 2011 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 // Alpha-plane decompression.
9 //
10 // Author: Skal (pascal.massimino@gmail.com)
11
12 #include <stdlib.h>
13 #include "vp8i.h"
14
15 #ifdef WEBP_EXPERIMENTAL_FEATURES
16
17 #include "zlib.h"
18
19 #if defined(__cplusplus) || defined(c_plusplus)
20 extern "C" {
21 #endif
22
23 //-----------------------------------------------------------------------------
24
VP8DecompressAlphaRows(VP8Decoder * const dec,int row,int num_rows)25 const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec,
26 int row, int num_rows) {
27 uint8_t* output = dec->alpha_plane_;
28 const int stride = dec->pic_hdr_.width_;
29 if (row < 0 || row + num_rows > dec->pic_hdr_.height_) {
30 return NULL; // sanity check
31 }
32 if (row == 0) {
33 // TODO(skal): for now, we just decompress everything during the first call.
34 // Later, we'll decode progressively, but we need to store the
35 // z_stream state.
36 const uint8_t* data = dec->alpha_data_;
37 size_t data_size = dec->alpha_data_size_;
38 const size_t output_size = stride * dec->pic_hdr_.height_;
39 int ret = Z_OK;
40 z_stream strm;
41
42 memset(&strm, 0, sizeof(strm));
43 if (inflateInit(&strm) != Z_OK) {
44 return 0;
45 }
46 strm.avail_in = data_size;
47 strm.next_in = (unsigned char*)data;
48 do {
49 strm.avail_out = output_size;
50 strm.next_out = output;
51 ret = inflate(&strm, Z_NO_FLUSH);
52 if (ret == Z_NEED_DICT || ret == Z_DATA_ERROR || ret == Z_MEM_ERROR) {
53 break;
54 }
55 } while (strm.avail_out == 0);
56
57 inflateEnd(&strm);
58 if (ret != Z_STREAM_END) {
59 return NULL; // error
60 }
61 }
62 return output + row * stride;
63 }
64
65 #if defined(__cplusplus) || defined(c_plusplus)
66 } // extern "C"
67 #endif
68
69 #endif // WEBP_EXPERIMENTAL_FEATURES
70