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Updated the near-lossless level mapping.

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Updated the near-lossless level mapping and make it correlated to lossy
quality i.e 100 => minimum loss (in-fact no-loss) and the visual-quality loss
increases with decrease in near-lossless level (quality) till value 0.

The new mapping implies following (PSNR) loss-metric:
-near_lossless 100: No-loss (bit-stream same as -lossless).
-near_lossless  80: Very very high PSNR (around 54dB).
-near_lossless  60: Very high PSNR (around 48dB).
-near_lossless  40: High PSNR (around 42dB).
-near_lossless  20: Moderate PSNR (around 36dB).
-near_lossless   0: Low PSNR (around 30dB).

Change-Id: I930de4b18950faf2868c97d42e9e49ba0b642960
This commit is contained in:
Vikas Arora
2015-02-05 11:16:37 -08:00
parent 19f0ba0eb9
commit 4c82284d2e
5 changed files with 13 additions and 8 deletions
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2
examples/cwebp.c
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@ -616,7 +616,7 @@ static void HelpLong(void) {
printf(" -noalpha ............... discard any transparency information\n");
printf(" -lossless .............. encode image losslessly\n");
printf(" -near_lossless <int> ... use near-lossless image\n"
" preprocessing (0=off..100)\n");
" preprocessing (0..100=off)\n");
printf(" -hint <string> ......... specify image characteristics hint,\n");
printf(" one of: photo, picture or graph\n");