Lossless JPEG transformations

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llpics
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Joined: Thu Aug 24, 2006 8:32 pm

Lossless JPEG transformations

Post by llpics » Fri Aug 25, 2006 8:39 pm

Didn't know where else to post this but.....
I wanted to say how extremely pleased I am with the newest version of XNView. Previously, I was using 1.74 ...yes, I know it was an old one.

I had intended to send a question about burning CD on the old version..but when I got to your site I saw there was a newer version. I downloaded and installed the newest V1.82.4. WOW!!! What a lot of changes and new stuff too!.

I haven’t had a chance to work thru them all yet. There are several features which I don’t even use because I do not understand all of the concepts. But I am working on some of them.

I don’t know if the column Comments (which I is see is embedded) was in the older versions of XNView. I never noticed it before. What is this column used for and can users enter data there?

If there is a site where you could guide me to read up on Jpeg lossless transformations, I would be most appreciative.

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XnTriq
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Re: XNView V1.892.4

Post by XnTriq » Fri Aug 25, 2006 10:00 pm

llpics wrote:I don’t know if the column Comments (which I is see is embedded) was in the older versions of XNView. I never noticed it before. What is this column used for and can users enter data there?
llpics wrote:If there is a site where you could guide me to read up on Jpeg lossless transformations, I would be most appreciative.
Last edited by XnTriq on Fri Jun 22, 2007 9:35 pm, edited 1 time in total.

llpics
Posts: 5
Joined: Thu Aug 24, 2006 8:32 pm

jpg loss-less

Post by llpics » Tue Aug 29, 2006 9:05 pm

many thanks for the GREAT link for info on .jpg lossless. it was very helpful.

would you suggest that I convert ALL my .jpg to .jpg lossless? Or is it a personal preference.

I have a variety of sources.... some from digital camera, some are scanned from hard copy photos and some are scanned from photo copied pictures and some are scans from newspapers.

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XnTriq
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Re: jpg loss-less

Post by XnTriq » Sat Sep 02, 2006 1:45 pm

Hi llpics,
llpics wrote:many thanks for the GREAT link for info on .jpg lossless. it was very helpful.
:)
llpics wrote:would you suggest that I convert ALL my .jpg to .jpg lossless? Or is it a personal preference.

I have a variety of sources.... some from digital camera, some are scanned from hard copy photos and some are scanned from photo copied pictures and some are scans from newspapers.
What exactly do you mean by “convert” and “.jpg lossless”?
To clear up possible misconceptions — if any — about “JPEG Lossless Transformations” (or “Transcoding”) I've compiled a list of links.

Hopefully I won't get kicked out for posting such a biggie. Image Image

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Forum references: Off-site resources: Freeware:
  • JPEGclub.org
    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):
    • jpegtran
      “The jpegtran command-line program is useful to optimize the compression of a JPEG file, convert between progressive and non-progressive JPEG formats, eliminate non-standard application-specific data inserted by some image programs, or to perform certain transformations on a file – such as grayscaling, or rotating and flipping (within certain limits) – all done ‘losslessly’ (i.e. without decompressing and recompressing the data, and so causing a reduction of image quality due to generation loss).” (Source: Wikipedia » libjpeg)
    • Jpegcrop – Preferences and Options description
      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.
  • Ben Jackson: “Lossless” cropping with jpegtran
    I have added a new option to jpegtran (part of the Independent JPEG Group's JPEG software) to cut regions out of an image without re-encoding the region. The region retains the exact same data it had in the main image with the restriction that the image can only be cropped along DCT block boundaries. My main use for this feature is modifying digital camera images which come out of the camera already JPEG compressed and need to be rotated and cropped for storage.
  • Matthias Wandel: jhead – Exif Jpeg header and thumbnail manipulator program
    Jhead is a command line driven program for manipulating the non-image parts of Exif flavour JPEG files that most digital cameras produce.
  • Toke Eskildsen: JPEGCrops – Cropping of JPEG images without loss of quality
    JPEGCrops is a Windows program, created for preparation of a batch of images for printing. It provides lossless cropping with fixed aspects using jpegtran.
  • TsuruZoh Tachibanaya: Rota
    Rota is simple and easy to use loss-less rotation utility for JPEG image.
    To get large compression ratio (about 1/5 to 1/50), JPEG uses lossy compression method. Therefore once image has been compressed to JPEG, it is not possible to retrieve original image from it. If you take a picture of some guy by vertical camera position, maybe you'd like to rotate image to stand it upright. In usual, it takes 3 steps to rotate JPEG image: de-compress JPEG to bitmap, rotate bitmap, re-compress bitmap to JPEG. This re-compress process cause additional loss of image quality.
  • AnRy: JPEG Lossless Rotator (utilizes XnView's GFL-SDK)*
    Have you ever thought that when you rotate a JPEG photo you lose its quality?
    When you want to rotate a JPEG image or photo, most image editors decode the image, rotate the bitmap and then reencode the JPEG. This process slightly decreases the final image quality. But, unlike other tools, this does not recode your image but performs a special lossless block transformation. As a result, the rotated image has exactly the same quality as the original. Two possible thumbnail quality/speed settings, shell integration feature (this allows you to rotate a JPEG image through a right-click on the file), batch rotation (from the shell), EXIF-data display, and favorite folders option. Free, simple, and useful.
    * jpgrotate.dll = libgfl254.dll
    jpegrotate.dll = libgfle254.dll

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