Help changing color of monotone images and shapes

[icantdie]

Please consider the following image in which all of the pixels are grey. How can I easily select all the grey pixels and turn them black? Thanks!

 

[PseFrank]

1. Open the image in Photoshop...CS, Elements, whatever.

2. In the layers palette click the "Create a new fill or adjustment layer" icon.

3. Choose "Threshold" from the menu.

4. Slide the slider to the right up to a value of around 220/225. (Different for every image)

5. Choose the Magic Wand from the toolbar and uncheck "Contiguous".

6. Click on a black section of the image.

7. Back in the layers palette highlight the background layer again.

8. With black as your foreground colour...Hit Alt + Backspace on the keyboard.

9. Hit Ctrl + D to turn off the selection.

10. Right click on the Threshold adjustment layer and select "Delete"

That's it..

 

[Trevor Dennis]

Levels. Move black slider to the right.

 

[Trevor Dennis]

I don't often use Threshold because it lacks even a modicum of subtlety. No trace of anti-aliasing for instance, so you end up with jaggy edges. If you look at the histogram in the Levels properties panel above, you can see the spike a third in from the right, that represents the grey tones. You can also see a low value ramp into the spike on the far right, which is the white tones. Not surprisingly, this value clips to the top of the histogram as there are a lot of whites in the image. But it is the very shallow values between those two spikes that are interesting, as they probably represent the noise, and perhaps some of the anti-aliasing around the borders of the grey tones. If you apply a threshold adjustment and look at the hostogram, it will look like a switch with values at each end and _nothing_ between them.