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Convert a PDF to grayscale
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Make a gray copy of a PDF file with sumatrapdf-tool recolor, or only view pages in gray in SumatraPDF with Toggle Grayscale.
Available in pre-release 3.7
To make a gray PDF file, run sumatrapdf-tool recolor -c gray -o gray.pdf color.pdf. At a glance:
  • Gray PDF file: sumatrapdf-tool recolor rewrites the colors of text, graphics and images as shades of gray.
  • View in gray: Toggle Grayscale (CmdToggleGrayscale) shows pages in gray on screen. The file doesn’t change.
  • Print in gray: monochrome in -print-settings, or print the gray PDF made by recolor.

Make a grayscale PDF file #

Use sumatrapdf-tool recolor, or SumatraPDF.exe recolor with the same arguments:
sumatrapdf-tool recolor -c gray -o report-gray.pdf report.pdf
  • Every page is converted: text, vector graphics and images.
  • -c gray is the default, so sumatrapdf-tool recolor -o report-gray.pdf report.pdf does the same.
  • Without -o the result is written to out.pdf in the current folder.
  • Add -r to also remove output intents (color profiles for print production).
  • The command prints nothing when it succeeds.
Open the new file in SumatraPDF to check it, or render a page to an image: sumatrapdf-tool draw -o check.png report-gray.pdf 1.
recolor can also convert to other color spaces: -c rgb or -c cmyk.
Note: colors of similar brightness become similar grays. In a test, red text, a blue box and green text came out as 47%, 35% and 52% gray, so a chart that relies on color alone can become hard to read.

View pages in grayscale in SumatraPDF #

Ctrl + K, then Toggle Grayscale in Command Palette. Run it again to go back to color.
  • It isn’t in any menu. To give it a shortcut, customize a keyboard shortcut for CmdToggleGrayscale.
  • It changes only how pages look on screen. The file isn’t modified and printing isn’t affected.
  • It applies to all documents and is remembered after restart: it’s saved as Grayscale in FixedPageUI in advanced settings. You can also set it there:
FixedPageUI [
    Grayscale = true
]
  • Only the page image is gray. Text selection, search highlights and other things drawn on top of the page keep their colors.
Toggle Grayscale doesn’t change the printout. Instead:
  • From the command line, add monochrome to -print-settings. It asks the printer driver to print in black and white:
SumatraPDF.exe -print-to "Office Printer" -print-settings "monochrome" report.pdf
  • In the print dialog (Ctrl + P), choose grayscale or black and white in the printer’s own options. The option’s name depends on the printer driver.
  • Or print the gray PDF made with recolor. That works with every printer.
See Printing for all print options.

Tips #

  • Use recolor before sending a document to a black-and-white printer or copier, to see how it will look.
  • Use Toggle Grayscale to read a colorful document with less distraction, without making a copy.
  • To make gray images of pages instead of a PDF, use sumatrapdf-tool convert -o page%d.png -O colorspace=gray report.pdf (see Convert PDF to images).
  • To convert a whole folder, see Process many PDFs at once.

See also #

SumatraPDF documentation
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Convert a PDF to grayscale
md