: How to convert grayscale bitmap to one CMYK color in Photoshop? How do you convert a grayscale bitmap a to one CMYK color in Photoshop for printing, eg. C61, M41, Y58, K16 green?

@Lengel450

Here's a trick I use for a lot of things, including your situation. I'm using Photoshop CS6 but this should apply to CS5 and earlier as well:

Prepare an inverted black and white image...


Convert to RGB if you're not already in RGB (Image > Mode > RGB)
I know you want to use a CMYK color, but just bear with me on this. The next couple of steps don't work in CMYK or Grayscale.
If the image is not already black and white, apply a Black & White adjustment layer (Layer > New Adjustment Layer > Black & White).
Next, apply an invert layer on top of that (Layer > New Adjustment Layer > Invert).
You should now have an inverted black and white image. The layers should be ordered, from top to bottom: Invert, Black & White, [your image]. Note: Your image should have started with a WHITE background, and should now have a BLACK background.


Convert the B&W image to a layer mask...


Merge the above mentioned layers together, including your base image (although I would duplicate them first, then merge the duplicates).
With the merged layer selected, select all pixels in the layer (Ctrl+A) and copy to the clipboard (Ctrl+C).
Open the Channels tab, and create a New Alpha Channel.
Paste the pixels into the new Alpha channel (Ctrl+V). Clear the original selection (Ctrl+D).
Load the Alpha Channel as a selection (in the bottom of the tool panel, it's the button with the dashed circle). You should see the "marching ants" in the shape of your image. You're almost there.
Create a new solid color fill layer (Layer > New Fill Layer > Solid Color...) and pick any color.


At this point you should have a semi-transparent layer in one color. Now you can add a white background underneath it, or leave it transparent, or burn it onto another layer for a cool effect.

In your case you need to convert the document back to CMYK and pick your final CMYK color...


Image > Mode > CMYK – Don't Merge and Don't Flatten.
Double-click the fill layer's icon to pick the exact CMYK color you want.

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@Gail6891361

For completeness, I'll add here that is not always necessary to alter the greyscale bitmap file. If it is in TIFF format and greyscale, and you are using a layout program (indesign, Quark, foo etc) you can use your layout program to tint the image to an exact swatch.

For indesign, you place the image, set the background color of the box to whatever (paper, black, red, purple etc), and then switch the context to the content of the box (aka the image is highlighted brown) and set the foreground color.

The greyscale image essentially acts as an alpha channel for the foreground color. (does not involve clipping paths etc.)

I like this method because it does not alter it (same as the accepted answer,which I upvoted), and it also ensures that the layout program uses the same CMYK or spot color values as all other items in the document (eliminates any chance of a profile or {magic} color adjustment).

In addition, if you change the swatch, it cascades the change throughout the document without the need to edit individually placed files.

Additionally in addition, you can use the same image without alteration with muliple color values. (Think Andy Warhol)

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@Speyer780

An alternative method, if you're not needing to print, is to use blending modes, this way you can pick your exact color:





Simply fill a layer and switch out your blending mode!

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@Voss6371140

The easiest way to do this is to open your image in grayscale mode in Photoshop (or convert to grayscale mode if it opens it in RGB/CMYK format).

From there, choose Image->Mode->Duotone.

Make sure the type is set to Monotone. Ink 1 will be set to black. Click on the black box, to access a color picker. Choose the color you want (use the color libraries button to get to the list of Pantone colors.) Click okay, and you are done!

Here's how it would look using the RGB values you specified.

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