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Assume that I have a png image of size 32x32(1024 pixels). It consists of x pixels with alpha > 60% and (1024-x) pixel with alpha < 25%. Could you please tell me how to remove all low-alpha( alpha < 25% ) pixel in image?

Is there anything like alpha range - color range in photoshop?

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Here's one way to do it:

  1. Extract the alpha channel, so it's a separate mask. Here's a way to separate the alpha.
  2. Edit the alpha channel, using levels or curves.

Does that help? Do you need more detail?

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    Pretty difficult to understand:((. I'm struggling a lot to solve this:D
    – wanting252
    Jul 24, 2012 at 11:01
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I would do what Marc suggested, though I also use the Refine Mask feature to directly alter the fringing amount around the edge of the mask rather than adjusting curves. It's quite powerful as you can tweak feathering, contract / expand, and also use Smart Radius to tackle things like fine hair strands. You can get to it either by going to the Masks palette in CS5 downward, or the Properties palette in CS6.

It's good for getting rid of white fringing around a coloured object, if that's the specific issue you're facing.

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    Yeah. I guess it depends on the source material and desired result.
    – Marc Edwards
    Jul 24, 2012 at 11:50

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