New answers tagged image-manipulation
It is like when background is white, ImageMagick detects that there are only two colors — black and white — and switches to a grayscale mode of PNG, hence the ugly result: To limit the ugliness of applying black and white to anti-aliased edges, you can disable anti-aliasing with +antialias: convert -density 300 -alpha remove -alpha off +antialias a.pdf ...
Not an imagemagic solution, but sips -r 90 *.JPG will rotate all images ending in .JPG 90 degrees. It's a good one liner.
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