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Showing posts from November, 2019

Converting pdf files to black and white

I recently downloaded a book from archive.org, and it was off-color and not easily printable (they used to provide black/white pdf files for books, but apparently they stopped doing so). I needed to convert it to a monochrome file so I could print it. This lead me down a number of dead-ends, and so I want to explain the best way I found to do this. First, convert each page to a separate PNG file. Here is the command I used: pdftoppm Hutchings.pdf file_prefix -png Note that you can make the file_prefix anything you would like. Next, you will need to determine the "threshold" at which point these pictures become black and white. Play around with it using this command: convert file_prefix-1.png -threshold 35% testing-1.png When you have determined the threshold, now it is time to batch processes all your PNG files (any files that need a different threshold can be individually adjusted using the above convert command. I use mogrify to do this, and I also make sure to