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Using ImageMagick to correct white balance in a batch of photos using a white reference

I had the problem of fixing the white balance in a set of photos I had taken with the camera settings wrong. I had "Tungsten light (Approx. 3200K)" selected on my Canon 700D, but I was taking photos outdoors, so I should probably have set it to "Daylight (Approx. 5200K)". The result was that all of the photos had a kind of blueish tint.

Using ImageMagick, I was able to correct the white balance for the whole set of files as follows:

• Using the same camera settings - "Tungsten light (Approx. 3200K)" on the Canon 700D - I created a white reference photo (white_reference.jpg) by taking a photo of a white piece of paper in similar outdoor lighting conditions.
• I made sure that the white paper occupied at least the centre 128x128 pixel region of the reference photo.
• I then used the script below (fixer.sh) to apply the colour correction to the full set of images (IMG*.JPG)

#!/bin/bash

for file in IMG*.JPG ; do echo $file ; convert $file \( +clone \( white_reference.jpg -gravity Center -crop "128x128+0+0" -scale "1x1" -negate \) +dither -interpolate Integer -clut \) -compose Overlay -composite ${file%.JPG}_WB.JPG ; done

The core of that script is from a solution suggested by user "stupid" on the ImageMagick web forum:

https://www.imagemagick.org/discourse-server/viewtopic.php?t=15564

I just wrapped it in a bash for loop.