imagemagick

Note: Big difference between mogrify and magick/convert - mogrify rewrites the original image (and hence cannot add prefix or copy file) whereas convert ‘converts’ to a different file (hence can provide filename etc)

Converting between formats

• png to pdf¹

  mogrify -quality 100 -density 200 -colorspace sRGB -flatten -format png *.pdf

• jpg to png (requires background when png background is transparent)

    convert output-file.png -background white -flatten output-file.jpg

Combining images

• Horizontally (into one row)
  convert input-1.png input-2.png +append append_result.png
• Vertically (into one column)
  convert input-1.png input-2.png -append append_result.png

Compressing jpgs

 mogrify -strip -interlace Plane -gaussian-blur 0.05 -quality 85% -adaptive-resize 50% *.jpg

Removed -sampling-factor 4:2:0 because it was messing with the color ratios for me. Blurring seemed to work well without any noticeable differences (at least to me).²

Inverting and colorizing images

convert image.jpg -negate negated-image.jpg

convert negated-image.jpg -colorize 0,50,0 colorized-image.jpg 

For pngs, add -colorspace RGB.³⁴ I tried making a negative out of pngs but it did not work.

Manipulating Tiffs

Compressing TIFs into a jpg:⁵

mogrify -quality 80 -colorspace sRGB -flatten -format jpg ../*.TIF

Using one channel to make TIFs grayscale:⁶

mogrify -fx 'b' -quality 80 -colorspace Gray -flatten -format jpg ../*_uv.TIF

Adding watermark

magick input.png -gravity SouthEast -append -pointsize "%[fx:h*0.02]" -annotate +0+2 'watermark' output.png

pointsize (fontsize) can be a number or it can be relative. %[fx:h*0.02] makes the pointsize 2% of the height of the image.⁷

Footnotes

1. combined from this and this ↩

2. https://stackoverflow.com/questions/7261855/recommendation-for-compressing-jpg-files-with-imagemagick ↩

3. https://superuser.com/questions/636742/gimp-command-line-how-to-invert-color-of-a-list-of-picture-and-modify-the-color ↩

4. https://stackoverflow.com/questions/40403424/selective-negative-image-with-imagemagick ↩

5. https://stackoverflow.com/questions/68773121/combining-tiff-files-by-channel-with-imagemagick ↩

6. https://stackoverflow.com/a/13346102 ↩

7. Guide for more complex watermarks can be found here ↩