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Two Issues with the JPEG Standard
This report is a follow­up to a recent security audit of a JPEG­implementing codebase, libjpeg­turbo, conducted by the audit firm Cure53 at the behest of Mozilla. It is concerned with two particular issues uncovered by the auditors. In examining the code, they were able to find two scenarios under which they could make the JPEG library consume resources significantly out of proportion to the size of the data being processed. While these were originally thought to be issues with the implementation, further investigation has revealed that they stem from the design of the JPEG format itself. The problems can be triggered using JPEG images which entirely conform to the spec, and the issues have been observed in multiple JPEG implementations. This report explains those two issues in detail and provides advice to application developers as to how to work around them if their applications are processing untrusted input.
jpeg  mozilla 
2 days ago by jchris
google/guetzli: Perceptual JPEG encoder
Could have sworn I bookmarked this before. May finally have a Google thing I use regularly again.
compression  jpeg  images  google 
4 days ago by rubenerd
is an open-source JPEG 2000 codec written in C language
jpeg  wavelets  jpeg2000  opensource  codec  library 
7 days ago by Z303
ImpulseAdventure - JPEG Compression and JPEG Quality
"When trying to resave a digital photo, one is often faced with a decision as to what "quality settings" (level of compression) to use. The JPEG file format (more properly JFIF), allows one to select an appropriate trade-off between file size and image quality. It is important to understand that JPEG (and nearly all lossy file formats) are not suitable for intermediate editing because of the fact that repeated saves will generally diminish the working file's quality. In addition to the cumulative introduction of visual artefacts (error), repeated recompression also introduces destructive color changes. It is for these reasons that "lossless" file formats (such as TIFF, PSD, BMP, etc.) are better choices for intermediate processing. JPEG should only be used for storing the final image (ie. after editing) and possibly the initial capture."
graphics  image  photo  compression  jpeg 
14 days ago by ddribin
ImpulseAdventure - 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."
photo  image  jpeg 
16 days ago by ddribin
ImpulseAdventure - JPEG / Exif Orientation and Rotation
"Many newer digital cameras (both dSLR and Point & Shoot digicams) have a built-in orientation sensor. Virtually all Canon and Nikon digital cameras have an orientation sensor. The output of this sensor is used to set the EXIF orientation flag in the image file's metatdata to reflect the positioning of the camera with respect to the ground."
photo  image  jpeg  exif 
17 days ago by ddribin
TinyPNG – Compress PNG images while preserving transparency
Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
JPEG  PNG  image  compress 
25 days ago by moyiciai
Preview - add an image to a PDF file - Mac OS X Hints
Use Formulate Pro (it's free) to do this and other markup on PDF's... I use it to fill out "pdf forms" all the time...
macosxhints  PDF  editing  JPEG 
6 weeks ago by rgl7194

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