JPEGclub.org develops new JPEG features and contributes to the Independent JPEG Group's (IJG) software.
New features and contributions have been developed for the three major parts of the IJG library: the compression, the decompression, and the transcoding parts. These parts are represented by the three major tools of the IJG software: cjpeg (compress JPEG), djpeg (decompress JPEG), and jpegtran (transcode JPEG - lossless):
Lossless rotation and related transforms have been added to the IJG software with release 6b of 27-Mar-1998.
New (08-Feb-2005):
An article about the jpegtran lossless transformation functions has been published in the German c't magazine 4/2005 (released 07-Feb-2005), title "Fotoschoner", page 188 ff. The article derives and describes the lossless transformation functions in a clear and understandable form.
My draft of the article (in German) is available here:
Verlustfreie_JPEG_Drehung.doc or Verlustfreie_JPEG_Drehung.pdf .
Note that the draft is quite different from the published version, but the essence is the same.
An Exif Patch has been added to the lossless
transformation code to avoid some application problems.
It is part of the release-candidate croppatch to jpegtran.
A new "-perfect" switch has recently been added to the lossless transformation support in jpegtran:
-perfect Fail if there is non-transformable edge blocks
The new switch is part of the release-candidate croppatch to jpegtran.
A new -crop option has been added to jpegtran for 'lossless' cropping of JPEG images:
-crop WxH+X+Y Crop to a rectangular subarea
This feature is in the release-candidate croppatch to jpegtran.
An extended feature set "Lossless crop 'n' drop" (cut & paste) has been added to jpegtran:
-crop WxH+X+Y Crop to a rectangular subarea
-drop +X+Y filename Drop another image
This extended feature set is still in experimental state, not yet release-candidate.
More about new jpegtran features...
The decompress part of the Independent JPEG Group library has got a direct rescaling feature while decoding with factors 1/2, 1/4, and 1/8.
This is interesting because different spatial size output can be retrieved directly from the JPEG (DCT) data without separate full decode and spatial resample.
Using a new method, this feature has now been extended to a broader and finer range of scaling factors: All scalings with factors N/8 with N=1...16 (downscale and upscale) are now supported with the djpeg -scale option or with setting the scale_num/scale_denom variables in library application.
Furthermore, the performance in the old cases (1/2, 1/4, 1/8) has been improved considerably with the new method.
More about new djpeg -scale N/8 with all N=1...16 feature...
Two new features have been added to the cjpeg tool and compression library:
-quality N[,...] Compression quality (0..100; 5-95 is useful range) -scale M/N Scale image by fraction M/N, eg, 1/2The -quality option has been extended for support of separate quality settings for luminance and chrominance (or in general, for every provided quantization table slot). This feature is useful for high-quality applications which cannot accept the damage of color data by coarse subsampling settings. You can now easily reduce the color data amount more smoothly with finer control without separate subsampling. The resulting file is fully compliant with standard JPEG decoders.
A new -scale option is provided with cjpeg which complements the corresponding djpeg -scale option. The supported range of scaling factors is 8/N with all N=1...16.
This means you can now easily alter the nominal spatial resolution of a given source image while compressing to JPEG without additional resampling.
For example, if you have an image sensor providing an effective capture resolution of 2268x1512 pixels (HI resolution), you can now directly generate a MED resolution of 1512x1008 pixels (-scale 2/3) and a LOW resolution of 1134x756 pixels (-scale 1/2) from the sensor source resolution with the library while compressing to JPEG without additional resampling.
(An efficient 12x12 FDCT is used in the -scale 2/3 case, and an efficient 16x16 FDCT is used in the -scale 1/2 case instead of the standard 8x8 FDCT inside the library, ensuring high-quality downscaled results - the resulting file is fully compliant with standard JPEG decoders.)
More about new cjpeg features...
The Jpegcrop Windows Application was initially developed to provide a convenient interactive user interface for the new jpegtran -crop feature.
It has now developed to a nearly complete user interface replacement for jpegtran, and furthermore for demonstration of the enhanced djpeg -scale feature.jpegcrop.zip
Jpegcrop Windows Application (jpegcrop.exe and jpegcrop.txt), latest release 2008.01.04.See also the Jpegcrop Preferences and Options description.
J P E G c r o p
News (05-May-2003):
The most wanted feature currently for Jpegcrop is a "constrained aspect ratio" crop mode. If you need such a function to crop your photo images to the common 10x15 (3:2) photo frame, have a look at Stefan Scherer's Jpegcrop with FotoFrame feature. This is a preliminary Jpegcrop extension until an 'official' version will be available someday. Thanks to Stefan Scherer for this contribution! See also the lossless rotation apps page for more solutions (jpegtran Frontends "FotoView" from Martin Pola and "JPEGCrops" from Toke Eskildsen).
This software featured by
Softpedia.
Nice presentation with
screenshots,
just after updating with new icons.
PC Magazine.
Simtel.Net.
Lockergnome.
Thank you Chris Pirillo for the unbelievable hit rate boost!
WebAttack.
CoMa's
Freeware List.
Freeware World Team.
About Graphics Software.
T.H.E Journal.
Photoworld.
Nice description with screenshots (German).