Select all transparent pixels in an image?

[alanterra]

Is there a way to select all transparent pixels in an image?

I have an image with lots of layers and lots of masks, and I want to select exactly the pixels that are 100% transparent in the image. (Or, alternatively, all the pixels that are not completely transparent).

I thought I could do this by creating a Fill Layer with a color that doesn't occur in the image, and then Select : Color Range… with a fuzziness of 0 and clicking on one of the colored pixels. But it turns out that this only partially selects the transparent pixels, unless the Fill Layer is Black or White. (Try it out, I was surprised by this behavior). There is also the problem that if you accidentally choose a color in the Fill Layer that happens to be in your image, you will perforce select those pixels too.

I have a way to do this that is a little convoluted, but I thought that there might be a one-step solution.

TIA

[Semaphoric]

Load the layer transparency as a selection. Enter Quick Mask mode. Image > Adjustments > Threshold [set to zero].  Exit Quick Mask.

[alanterra]

Sorry, Semaphoric, I'm not sure if you didn't understand me, or I'm not understanding you. I want to select all the transparent pixels in a document (multiple layers in a document), not a layer.

[Semaphoric · Accepted solution]

Wasn't at the computer before, so I couldn't check, but this seems to work (you can make a Action of it):

1. With all layers visible, Stamp Visible (Control+Alt+Shift+E)
2. Select Transparency of the stamped layer
3. Enter Quick Mask
4. Invert
5. Threshold = 255
6. Exit Quick Mask
7. [Optional] Delete the new layer.

You could change the location of the Invert step, but you may have to change to Invert Selection and/or Threshold = 1.

[alanterra]

I tried exactly that, but I misunderstood something and thought it would not work. It does. Thank you!

[Justplainpeeved]

Any Chance this works on Mac? What would the related hotkeys be?