MobileRead Forums - View Single Post - Dealing with white text on colored background when prepping PDFs for grayscale or B&W

JawadLeLogeur · 10-24-2025, 12:13 PM

This is mostly so that I can print a bunch of docs on my grayscale printer without using too much toner.

I've already found a number of solutions to convert a color PDF into pure B&W (as opposed to grayscale) which is ideal when the file only contains dark text on light background.

I'm running into issues when dealing with PDFs that feature BOTH color/000000 text on light/FFFFFF background and light/FFFFFF text on color/000000 background. The threshold function preserves the former as 000000 on FFFFFF but turns the latter into FFFFFF on 000000 which wastes a ton of toner. If I set the threshold too low, the text simply disappears. I can tweak grayscale of course, but it still leaves a ton of background grey that is not necessary. I will have to deal with close to a thousand pages so this is significant.

I'm looking for a method that can turn both portions that are light/FFFFFF text on color/000000 background and those that are color/000000 text on light/FFFFFF background into dark grey/000000 text on FFFFFF background.

It's okay if the end result looks nasty as long as the information on the page is legible. I can do conversions manually but if there is a way to batch these that would be awesome as well.

10-24-2025, 12:13 PM	#1
JawadLeLogeur Zealot Posts: 110 Karma: 7156 Join Date: Jun 2017 Location: Western Sahara Device: Kobo Forma 4.15.12920	Dealing with white text on colored background when prepping PDFs for grayscale or B&W This is mostly so that I can print a bunch of docs on my grayscale printer without using too much toner. I've already found a number of solutions to convert a color PDF into pure B&W (as opposed to grayscale) which is ideal when the file only contains dark text on light background. I'm running into issues when dealing with PDFs that feature BOTH color/000000 text on light/FFFFFF background and light/FFFFFF text on color/000000 background. The threshold function preserves the former as 000000 on FFFFFF but turns the latter into FFFFFF on 000000 which wastes a ton of toner. If I set the threshold too low, the text simply disappears. I can tweak grayscale of course, but it still leaves a ton of background grey that is not necessary. I will have to deal with close to a thousand pages so this is significant. I'm looking for a method that can turn both portions that are light/FFFFFF text on color/000000 background and those that are color/000000 text on light/FFFFFF background into dark grey/000000 text on FFFFFF background. It's okay if the end result looks nasty as long as the information on the page is legible. I can do conversions manually but if there is a way to batch these that would be awesome as well.