diff options
| author | dcommander <dcommander@3789f03b-4d11-0410-bbf8-ca57d06f2519> | 2011-02-18 03:19:43 +0000 |
|---|---|---|
| committer | dcommander <dcommander@3789f03b-4d11-0410-bbf8-ca57d06f2519> | 2011-02-18 03:19:43 +0000 |
| commit | dc230d7293f5676a6be16d3886879c50c19887fe (patch) | |
| tree | 1b6f110f842612169047fb29ed65399f12900f8c /branches | |
| parent | d8972a1119d8681244978dde4adb1a49ca56730b (diff) | |
The fast integer DCT degrades for qualities > 95, so use the slow integer DCT instead to ensure that perceptually lossless performance is maintained.
git-svn-id: https://libjpeg-turbo.svn.sourceforge.net/svnroot/libjpeg-turbo@381 3789f03b-4d11-0410-bbf8-ca57d06f2519
Diffstat (limited to 'branches')
| -rw-r--r-- | branches/1.0.x/ChangeLog.txt | 8 | ||||
| -rw-r--r-- | branches/1.0.x/turbojpegl.c | 3 |
2 files changed, 9 insertions, 2 deletions
diff --git a/branches/1.0.x/ChangeLog.txt b/branches/1.0.x/ChangeLog.txt index d82b0f6..a1ad2e4 100644 --- a/branches/1.0.x/ChangeLog.txt +++ b/branches/1.0.x/ChangeLog.txt @@ -3,7 +3,13 @@ [1] Added further protections against invalid Huffman codes. -[2] Fixed visual artifacts in grayscale JPEG compression caused by a typo in +[2] 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. + +[3] Fixed visual artifacts in grayscale JPEG compression caused by a typo in the RGB-to-chrominance lookup tables. diff --git a/branches/1.0.x/turbojpegl.c b/branches/1.0.x/turbojpegl.c index 2150a2d..eeaedd1 100644 --- a/branches/1.0.x/turbojpegl.c +++ b/branches/1.0.x/turbojpegl.c @@ -166,7 +166,8 @@ DLLEXPORT int DLLCALL tjCompress(tjhandle h, jpeg_set_colorspace(&j->cinfo, JCS_GRAYSCALE); else 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[1].h_samp_factor=1; |