diff options
-rw-r--r-- | zlib.h | 27 |
1 files changed, 15 insertions, 12 deletions
@@ -587,18 +587,21 @@ ZEXTERN int ZEXPORT deflateInit2(z_streamp strm, | |||
587 | 587 | ||
588 | The strategy parameter is used to tune the compression algorithm. Use the | 588 | The strategy parameter is used to tune the compression algorithm. Use the |
589 | value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a | 589 | value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a |
590 | filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no | 590 | filter (or predictor), Z_RLE to limit match distances to one (run-length |
591 | string match), or Z_RLE to limit match distances to one (run-length | 591 | encoding), or Z_HUFFMAN_ONLY to force Huffman encoding only (no string |
592 | encoding). Filtered data consists mostly of small values with a somewhat | 592 | matching). Filtered data consists mostly of small values with a somewhat |
593 | random distribution. In this case, the compression algorithm is tuned to | 593 | random distribution, as produced by the PNG filters. In this case, the |
594 | compress them better. The effect of Z_FILTERED is to force more Huffman | 594 | compression algorithm is tuned to compress them better. The effect of |
595 | coding and less string matching; it is somewhat intermediate between | 595 | Z_FILTERED is to force more Huffman coding and less string matching than the |
596 | Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY. Z_RLE is designed to be almost as | 596 | default; it is intermediate between Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY. |
597 | fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data. The | 597 | Z_RLE is almost as fast as Z_HUFFMAN_ONLY, but should give better |
598 | strategy parameter only affects the compression ratio but not the | 598 | compression for PNG image data than Huffman only. The degree of string |
599 | correctness of the compressed output even if it is not set appropriately. | 599 | matching from most to none is: Z_DEFAULT_STRATEGY, Z_FILTERED, Z_RLE, then |
600 | Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler | 600 | Z_HUFFMAN. The strategy parameter affects the compression ratio but never |
601 | decoder for special applications. | 601 | the correctness of the compressed output, even if it is not set optimally |
602 | for the given data. Z_FIXED uses the default string matching, but prevents | ||
603 | the use of dynamic Huffman codes, allowing for a simpler decoder for special | ||
604 | applications. | ||
602 | 605 | ||
603 | deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough | 606 | deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough |
604 | memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid | 607 | memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid |