Lossless JPEG transformations

[llpics]

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.

[XnTriq]

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?

• General Support
  • Editing EXIF comment

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

• Online-Help
  • JPG Lossless Transformations

[llpics]

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.

[XnTriq]

Hi llpics,

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.

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.

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Forum references:

• JPEG compression as lossless as possible
• What format should I save this image in?
• Lossy? Lossless? 256 colors? This is confusing!
• JPG lossless crop more accurate on right.
• JPEG lossless transformations UGLY BUG?
• Jpg compression after crop
• JPG Lossless Transformations

Off-site resources:

• Wikipedia – The free encyclopedia that anyone can edit
  • Image file formats / Graphics file format summary
    • JPEG (» libjpeg)
    • JPEG-LS
    • JPEG-2000
    • DjVu
    • TIFF (» libtiff)
    • PNG (» libpng)
  • Image compression
    • Lossless
    • Lossy
    • Generation loss
    • Wavelet
    • LZW
    • DEFLATE (» zlib + ZIP)
• About.com – The Human Internet
  Expert guidance from real people searching the Internet for the information, goods, and services that you need to know related to your passion
  • Graphics Software
    • Working with Digital Photos and Scanned Images
      • Q&A: Does Rotating Images Degrade Image Quality?
    • Graphics File Formats and Types of Computer Graphics
      • JPEG and JPEG 2000
        • JPEG Myths and Facts: Page #1 + Page #2
          The JPEG image format has quickly become the most widely used digital image format. It's also the most misunderstood. Here's a collection of some common misconceptions and facts about JPEG images.
        • The Pitfalls of JPEG Compression
          JPEG compression makes your pictures nice and small so you can fit more on your storage card, but too much compression can damage them beyond repair. Your camera probably offers options to let you choose the best compromise between image quality and file size.
  • Focus on Linux
    • Linux / Unix Command Library (Man Pages)
      • jpegtran
        jpegtran performs various useful transformations of JPEG files. It can translate the coded representation from one variant of JPEG to another, for example from baseline JPEG to progressive JPEG or vice versa. It can also perform some rearrangements of the image data, for example turning an image from landscape to portrait format by rotation.
        jpegtran works by rearranging the compressed data (DCT coefficients), without ever fully decoding the image. Therefore, its transformations are lossless: there is no image degradation at all, which would not be true if you used djpeg followed by cjpeg to accomplish the same conversion. But by the same token, jpegtran cannot perform lossy operations such as changing the image quality.
      • jhead
        jhead is used to display and manipulate data contained in the Exif header of JPEG images from digital cameras. By default, jhead displays the more useful camera settings from the file in a user-friendly format.
        jhead can also be used to manipulate some aspects of the image relating to JPEG and Exif headers, such as changing the internal timestamps, removing the thumbnail, or transferring Exif headers back into edited images after graphical editors deleted the Exif header. jhead can also be used to launch other programs, similar in style to the UNIX find command, but much simpler.
• TASI – Technical Advisory Service for Images
  A national service set up to advise and support the UK's academic community on the digital creation, storage and delivery of image-related information
  • Creating Digital Images
    • File Formats and Compression: Introductory Information / In-depth Report
    • New Digital Image File Formats
    • Choosing a File Format
    • Which digital camera file formats should I use?
    • What is the best format in which to archive my digital images?
    • The PNG file format
    • What is wavelet compression?
• ScanTips.com – Scanning Basics 101
  • Image File Formats – which to use?
    • JPEG (Joint Photographic Experts Group)
      • JPEG Artifacts: Page #1 (» JPEG Lossless Rotation) + Page #2
    • TIFF (Tag Image File Format)
• Steve's Digicams – Digital camera reviews
  • Tech Corner
    • October 2004: JPEG Images – Counting your Losses
    • August 2005: Whatever Happened to JPEG2000?
• ePaperPress: Photoshop for Photographers
  • Exporting Files » Archiving
    After color-correcting an image, and before resizing, save a copy of your work in a new file. Leave the original untouched – that's your “digital negative”. Later you can reload the archived copy and resize/sharpen for the intended target.
• ImpulseAdventure: Digital Photography Articles
  • JPEG Lossless Rotation, Lossless Crop
    With a photographer's desire to preserve the digital negatives as much as possible, there is a strong need to be able to rotate photos without reducing the quality in the process. The rotation might be done for a variety of reasons, including: correctly orienting a vertical portrait shot when the camera doesn't have a built-in orientation sensor, rotation for stylistic reasons, true rotation to match the EXIF orientation flag, etc. Similarly, one may want to crop a photo without degrading the quality of the uncropped portions of the image.
    As the “loss” (more properly: additive compression error) is completely dictated by the details of how JPEG compression works, it is important to understand some of the basic concepts.
    • How to test?
      With all of the concern about lossless rotation, it's worth knowing whether or not your particular software is capable of rotation without incurring additional compression error. It is virtually impossible to do this visually, and so a more object means must be used to perform this check. Fortunately, it is very easy to do, and I describe two of these methods below.
  • JPEG Lossless Rotation or Flip with Partial MCU
    As described on the JPEG Lossless Rotation page, it is not possible to rotate some images losslessly. Images that have dimensions that are not a multiple of the MCU dimension (typically 8x8 pixels) will not be rotated or flipped losslessly. This page explains the reasons why.

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)
    • Lossless jpegtran applications (» XnView)
      Here is a list of applications which provide the JPEG lossless rotation feature based on the IJG code.
  • 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