Graphic Design Stack Exchange is a question and answer site for Graphic Design professionals, students, and enthusiasts. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I need to know the color-values of a certain pixel in a PNG including the alpha value. But if I use pixelmator's color picker, the alpha value is not available.

Where can I find that information?

share|improve this question
Regarding a question regarding pngs and alpha channels a while back, I wrote a simple PHP script which IIRC could extract the alpha channel. If this might be useful to you, I can dig it up. – horatio Mar 2 '12 at 15:20
Thanks, I am a developer too and have written those scripts as-well. – vikingosegundo Mar 2 '12 at 16:01

I don't believe it's possible to use the eye dropper in Pixelmator to find this out (tested in Pixelmator 2.02 with Lion).

You could sample the colour, then create a new layer and paint a small square next to the colour you're trying to match, then adjust the opacity of the layer until they match perfectly. That would require a bit of patience though.

Acorn's eye dropper does pick up opacity and colour, so that's an option if you own it.

Photoshop's eye dropper doesn't pick up opacity, but it's possible to see the opacity in the info panel (if you have it set up to show opacity). You can also command-click a layer's thumbnail in Photoshop, then save the selection and interrogate the channel it saved, if you wanted to check out the entire alpha channel.

share|improve this answer
I'd agree. Pixelmator is nice, but hardly robust. The color picker is rudimentary and, I believe, is taking a reading of the literal pixel as rendered by the OS, not as it is 'built' within the PXM file itself. A bit frustrating, for sure. – DA01 Apr 1 '12 at 22:30
Acorn's eye dropper doesn't seem to work this way for me: it always shows 100% opacity (tested with 4.3.1 and 4.4, running on 10.8.5). Also, it gives different values when over the different parts of the grey / white chequerboard. Am I missing something? – Ashley May 27 '14 at 19:52

This question has been baking my noodle for some time and I have done some experimenting in Photoshop. Perhaps it isn't too different in Pixelmator. This is my solution:

I duplicated the transparent Layer till the transparency was entirely gone. Then I measure the pixel again with its now darker and non-transparent value.

Then I filled a new layer in the resulting color and slowly reduced the Opacity till they matched. And the result was pretty damn close.

Hope that helps. I can post a screenshot if you'd like or if something is unclear.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.