On Thu, 11 Dec 2008 16:49:27 +0100, Mike wrote:
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How would i go about picking/viewing the alpha value of a pixel in photoshop cs4? Hope it makes sense.
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The easiest way to manipulate the transparency of an image is to alt-double click the layer to change it to a normal layer,and use a layer mask. You can alt click on the layer mask and treat it as you would a normal image.
If you have existing images that you need to deal with, that use Photoshop’s layer transparency feature, things are little more problematic. Photoshop does not provide direct access to the transparency of a pixel. There is at least one plugin – alas the name escapes me – that does provide access to the per layer transparency information.
One way to calculate this is to copy the layer in question to a new document with a black background, lock transparency in the layer palette, and fill the layer with white. The info palette will then give a direct alpha value, 0-255, of the corresponding location on the original image.
Likewise, there is no direct way to set the transparency of a pixel, though you can change the transparency of a layer via the layer mask slider. To set the transparency of a layer that may contain partly transparent pixels, to a constant value, paste it to a layer that has been locked to the appropriate transparency.
If you set the transparency to zero, the pixel data will be lost. Photoshop will automatically set the pixel’s color values to zero. —
Mike Russell –
http://www.curvemeister.com 
