Creating compatible JPEG images (tip)

[wdimmit]

After a bit of trial and error, I've sorted out how to create readJPEG compatible JPEG images from the command line. Requires ImageMagick.

convert image.jpg -sampling-factor 1x1 -define jpeg:extent=5000b image_encoded.jpg

The key here is -sampling-factor 1x1 without it, the tool produces incompatible images (H2V2, I think). Also useful is -define jpeg:extent=5000b which adjusts the quality parameter as needed to cram the image into a limited file size.

[phoddie]

Tip is great, thank you. It was also a good motivation to implement H2V2 subsampling in commodettoReadJPEG.c. That's there now.