iOS 7 JPEG Decoding Bug Demo

• JPEG images with baseline compression have a decoding bug in iOS 7 (progressive files are not affected).
• The bug differs between different iOS devices.
• On an iPad Air or an iPad Mini 2 this will happen: (Demo 1)
  • The images will be chroma-subsampled and the colors become blur.
  • Images with odd widths will miss a 1px column at the right and the image will be stretched horizontally.
  • Images with odd heights will miss a 1px row at the bottom and the image will be stretched vertically.
  • It seems that only images that are roughly larger than ~98000 pixels (width x height) are affected.
• On an iPad 3 or iPhone 5 this will happen: (Demo 2)
  • Every second chroma row and line will be skipped.
  • It seems that this will only happen on larger images.

Live Bug Demos

• There are two images in each demo - a progressive and a baseline JPEG (both compressed with 100% quality and no color-subsampling).
• The images will swapped every second.
• There should be no visual difference between both images.

Demo 1: (for iPad Air and iPad Mini 2)

• The images have a size with an odd height - 512 x 321 pixel.
• The chroma will be subsampled (blurred and shifted red colors).
• At the bottom one 1px row will be missing (because of the odd height).
• The image will be stretched vertically (by this missing 1px row).
• Test this on an iPad Air or iPad Mini 2, an iPad 3 will be fine here.

Demo 2: (for iPad 3 and iPhone 5)

• Every second chroma row and line will be skipped.
• The images have a size even sizes - 512 x 512 - so there is no stretching here.
• Test this on an iPad 3 or iPhone 5, an iPad Air will be only chroma blurred.

Screenshots

• screenshot-ipadair.png - Demo 1 screenshot from an iPad Air.
• screenshot-ipad3.png - Demo 2 screenshot from an iPad 3.

Download Demos

• ios7-jpeg-decoding-bug-demos.zip - This whole page including the sample images.

Bug Report