Converting RAW images to lossless jpeg using GIMP?

Question

I have a Raw image which I want to get printed. I need to upload this to a website which expects to be in jpeg format.

I use GIMP for photo editing and used UFRaw to view RAW images.

GIMP cannot read Raw files directly, so I used UFRaw to view RAW image and save option saved it in ppm format, then I opened it in GIMP, did some editing and wanted to save the image. Saving in jpeg format compressed size from 10Mb to 3.6Mb

I did not want any compression of the image, I had option of saving in png, but I want lossless jpeg. How one can save in lossless jpeg format.

I use Ubuntu, GIMP, have UFRaw.

Asked by sat

Answer

Almost nobody uses lossless JPEG -- it's used within the DNG file format, and for some medical imaging applications, but that's about it. The probability that a file created with a JPG or JPEG extension in lossless JPEG format will be readable at the other end approaches 0 with a high degree of confidence. As for compression, well, almost all image file formats other than uncompressed TIFF will exhibit file size compression.

Unless all of your details are 1 pixel in size, a superfine JPEG compression (the highest quality the editor will permit -- that would be "quality level 12" in Photoshop, quality level 100 in the GIMP would be similar) will have so little loss that you wouldn't notice it without doing a pixel-by-pixel mathematical comparison (image subtraction). The alternative, if your service permits it, would be TIFF, but you'd want to compress that with the LZW option (lossless compression) to make the file size manageable. (It will still be much larger than a JPEG.)

Answered by Stan Rogers

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