Legacy ImageMagick Discussions Archive

I opened the pdf in photoshop and hovered over the background color, ie non-text area, and viewed the rgb values in the info window. They read r=22,g=22,b=22. After running magick input.pdf output.pdf, I examined output.pdf in the same way and read r=29,g=29,b=29. I just want to know where to set my ...

Having thought about it some more, I decided instead to use -black-threshold "%%[fx:mean<0.5?15:0]%%" before -level so that I could avoid using a variable. This way the background is set to black before inverting it to white.

One confusing issue, before conversion the background color was 22, but ...

Having thought about it some more, I decided instead to use -black-threshold "%%[fx:mean<0.5?15:0]%%" before -level so that I could avoid using a variable. This way the background is set to black before inverting it to white.

One confusing issue, before conversion the background color was 22, but ...

That does it. Thanks very much for all your help.

Ok that works now, thanks.

One last issue - the level command seems to cause a problem with the anti-aliasing. I noticed the output pdf has reduced image dimensions and file size. Not sure why?

Thank you GeeMack, I'm getting close now. I have:

magick input.pdf -channel RGB -level "%%[fx:mean<0.5?100:0]%%" output.pdf

which negates only the dark pages. Only one parameter needed for level, since white point is the opposite of black point.

However, I also wanted to add -white-threshold 85 ...

I'm getting an error:

convert: invalid argument for option '-level': %[fx:mean<0.5?100:0]% @ error/convert.c/ConvertImageCommand/2003.

Can fx be used to supply an argument for level? Or am I not formatting it correctly? Trying it manually on command line for now.

In a batch file I'm using:

magick convert %1 -alpha deactivate -negate -white-threshold 85%% "%~dpn1_negated%~x1"

which inverts all the pages of the input.pdf to the output.pdf

I'm trying to convert a pdf where some pages have white text on dark background. I can successfully convert single pages using -negate, but how can I conditionally process all pages, only converting those with a dark background? IM 7.0.7-Q16 on Win 10 64bit. Many thanks.