ryan/mozjpeg
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

The fast integer DCT degrades for qualities > 95, so use the slow integer DCT instead to ensure that perceptually lossless performance is maintained.

Browse Source
This commit is contained in:
DRC
2011-01-25 06:52:31 +00:00
parent 9ca11b80fc
commit 21b5c4bc4d
2 changed files with 12 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
ChangeLog.txt
View File

@@ -1,3 +1,13 @@
Significant changes since 1.0.90
================================
[1] Since the fast integer forward DCT seems to degrade for JPEG qualities
greater than 95, TurboJPEG/OSS will now automatically use the slow integer
forward DCT when generating JPEG images of quality 96 or greater. This
reduces compression performance by as much as 15% for these high-quality images
but is necessary to ensure that the images are perceptually lossless.
Significant changes since 1.0.1 Significant changes since 1.0.1
=============================== ===============================

3
turbojpegl.c
View File

@@ -193,7 +193,8 @@ DLLEXPORT int DLLCALL tjCompress(tjhandle h,
jpeg_set_colorspace(&j->cinfo, JCS_GRAYSCALE); jpeg_set_colorspace(&j->cinfo, JCS_GRAYSCALE);
else else
jpeg_set_colorspace(&j->cinfo, JCS_YCbCr); jpeg_set_colorspace(&j->cinfo, JCS_YCbCr);
j->cinfo.dct_method = JDCT_FASTEST; if(qual>=96) j->cinfo.dct_method=JDCT_ISLOW;
else j->cinfo.dct_method=JDCT_FASTEST;
j->cinfo.comp_info[0].h_samp_factor=hsampfactor[jpegsub]; j->cinfo.comp_info[0].h_samp_factor=hsampfactor[jpegsub];
j->cinfo.comp_info[1].h_samp_factor=1; j->cinfo.comp_info[1].h_samp_factor=1;