Saving a lossless JPEG

by XnTriq (Posted Mon Mar 14, 2016 4:45 pm)
To minimize so-called generation loss associated with the JPEG format, it usually is recommended to resave the image with the same settings that were used when the file was created.
The most important settings are quality factor (ranging from 0 to 100) and chroma subsampling.
Follow these step-by-step instructions to find out which settings were used to save a particular JPEG:

1. Download JPEGDUMP.ZIP and extract it to a new folder (e.g. X:\Test\).
2. Copy the JPEG file in question (e.g. sample.jpg) to X:\Test\.
3. Hit Win+R on your keyboard to open the Run dialog.
4. Type cmd and hit Enter to get to the command prompt.
5. At the command prompt, type X:\Test\JPEGDUMP.EXE "X:\Test\sample.jpg">X:\Test\jpegdump.log and hit Enter.
6. Post the contents of jpegdump.log.

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