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https://github.com/webmproject/libwebp.git
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70 lines
2.0 KiB
C
70 lines
2.0 KiB
C
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// Copyright 2011 Google Inc.
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//
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// This code is licensed under the same terms as WebM:
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// Software License Agreement: http://www.webmproject.org/license/software/
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// Additional IP Rights Grant: http://www.webmproject.org/license/additional/
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// -----------------------------------------------------------------------------
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//
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// Alpha-plane decompression.
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//
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// Author: Skal (pascal.massimino@gmail.com)
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#include <stdlib.h>
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#include "vp8i.h"
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#ifdef WEBP_EXPERIMENTAL_FEATURES
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#include "zlib.h"
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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//-----------------------------------------------------------------------------
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const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec,
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int row, int num_rows) {
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uint8_t* output = dec->alpha_plane_;
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const int stride = dec->pic_hdr_.width_;
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if (row < 0 || row + num_rows > dec->pic_hdr_.height_) {
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return NULL; // sanity check
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}
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if (row == 0) {
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// TODO(skal): for now, we just decompress everything during the first call.
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// Later, we'll decode progressively, but we need to store the
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// z_stream state.
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const uint8_t* data = dec->alpha_data_;
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size_t data_size = dec->alpha_data_size_;
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const size_t output_size = stride * dec->pic_hdr_.height_;
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int ret = Z_OK;
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z_stream strm;
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memset(&strm, 0, sizeof(strm));
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if (inflateInit(&strm) != Z_OK) {
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return 0;
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}
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strm.avail_in = data_size;
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strm.next_in = (unsigned char*)data;
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do {
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strm.avail_out = output_size;
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strm.next_out = output;
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ret = inflate(&strm, Z_NO_FLUSH);
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if (ret == Z_NEED_DICT || ret == Z_DATA_ERROR || ret == Z_MEM_ERROR) {
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break;
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}
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} while (strm.avail_out == 0);
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inflateEnd(&strm);
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if (ret != Z_STREAM_END) {
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return NULL; // error
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}
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}
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return output + row * stride;
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}
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#if defined(__cplusplus) || defined(c_plusplus)
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} // extern "C"
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#endif
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#endif // WEBP_EXPERIMENTAL_FEATURES
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