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 (at) 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 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
