Free Scripts to Convert Color Images to Grayscale

Keith Gilbert

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While creating a series of presentation templates for a client, I hammered together a couple of scripts that I thought I’d share. The scripts are free, and you can download them here.

The first script, Convert image to grayscale, simply converts any selected color image to a grayscale appearance. Appearance is the important word here, as the result isn’t a true grayscale image…it only appears to be grayscale. The script is intended for use in documents that will be shared digitally, for presentations, for PDFs, for printing locally to desktop color printers, etc. You’ll be disappointed if you try to create four-color separations from the output! If you’re looking for a script that will convert a color image to an actual CMYK-printable true grayscale image, try the Color2Gray script from Rorohiko, discussed in this post.

The second script, Convert image to grayscale with color background, asks you to choose a color from your swatches, and then converts the image to grayscale and composites it on a background of the color you chose, creating a sort of monotone effect.

How do these scripts work? The Convert image to grayscale script simply automates what you can do by hand: fills the frame with black, and changes the blend mode of the graphic to luminosity. The Convert image to grayscale with color background script does a bit more:

1. Fills the frame with black
2. Changes the blend mode of the graphic to luminosity
3. Changes the blend mode of the frame to multiply
4. Changes the opacity of the frame to the value you specify
5. Creates a new frame, and sends it behind the selected frame
6. Fills this new frame with the color you specify
7. Groups both frames together

The images that result from both scripts will look best on-screen if you choose Edit > Transparency Blend Space > Document RGB in InDesign.

I’m distributing both of these scripts “unlocked” in editable form. They are both quite simple, and I expect some may wish to edit these scripts and adapt them to their needs. If you want to try this, you’ll find the code fairly simple to follow and well-commented. Want to learn more about how to edit InDesign scripts? Watch my InDesign Scripting Made Easy course on Lynda.com or LinkedIn Learning.