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> lossless storage:

> to make JPEG store data losslessly: use grayscale, 100% quality, then either width or eight to 1 pixel, or duplicate the padded data 8 times (JPEG images are stored in 8x8 blocks).

Interesting. I wonder if this is used internally in any applications.

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Actually - JPEG is not lossless even at 100% quality, there is a little noise at +/-1 of pixel value, some rare pixels at 2. Grayscale is not needed, you may skip RGB->YUV conversion and encode in RGB colors, libjpeg can do that.

1 - No.

2 - JPEG algorithm allows to have lossless data without padding

3 - For lossless data rar/arc/ace are better then JPEG

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