JPEG is recompressed after setting IPTC/DPI metadata

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JPEG is recompressed after setting IPTC/DPI metadata

Post by fredrik »


Is it possible to avoid re-compression of a JPG image when setting metadata and dpi and maintain a somewhat original filesize?

Since it seems I cannot add dpi with the same command I am setting metadata with, I have two commands that I execute:

#1 Setting IPTC

Code: Select all

.../nconvert_6.50_win64/nconvert.exe -v -overwrite -iptc_clear 25 -iptc_add 25 "keyword 1" -iptc_add 25 "keyword 2" -iptc_set 105 "headline title"  -iptc_set 115 "asset name" -iptc_set 90 "city name" image.jpg
#2 Setting DPI

Code: Select all

.../nconvert_6.50_win64/nconvert.exe -v -overwrite -dpi 300 image.jpg

After having executed the first command, which sets a lot of IPTC, the image colors are every so slightly changed.
But after having performed the second command, which sets the DPI, the image colors are heavily changed.

I am rendering the original JPG out of The Foundry's Nuke, and with a 4:4:4 sub-sampling setting. I have attached a screenshot, where you should be able to see a little difference between left/right of the crosshair. The right hand side is the original image with colors untouched. On the left hand side is the image which has had command #1 and #2 applied. On my calibrated monitor, the discrepancy is greater than in that screenshot.

Please let me know if there is anything I can do set IPTC and DPI without touching the colors and maintaining a somewhat original file size.

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Re: JPEG is recompressed after setting IPTC/DPI metadata

Post by XnTriq »

Hello fredrik

Unfortunately I don't have an answer to your question regarding IPTC, but perhaps you're interested in the following info about DPI/PPI which I found very useful:
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Re: JPEG is recompressed after setting IPTC/DPI metadata

Post by xnview »

could you send me the original picture file?