JPEG lossless negatives ???

[piano632]

Don't know where else to ask this but... Is it possible to make a negative image of a JPEG photo without having to re-encode? I don't know how JPEG compression works, but it seems like there should be a way to simply invert the colors and save without re-encoding at a % quality.

[redwudz]

MS Paint>Image>Invert Colors. You will have to save it, but I don't know that there is any quality loss. Try inverting one, save it and check the size. Put it back in Paint, invert the colors again and see if it goes back to the original size and quality. The size at least goes back to the original. Magnify it and see if the quality does.

[racer-x]

Save it as a tiff. It can have some compression yet remain lossless. It will be a bigger file size however.

[piano632]

Well, using MS Paint I started with a 131KB photo... inverted colors, saved and got a 118KB photo... used that photo to invert back to original colors and got a 117KB photo. So I don't think it's lossless.

[greymalkin]

can you see the difference? What is the real reason for needing it to be lossless?