Black tractor wrote:
How to use , on where, what purpose?? thanks
This is what the manual would tell you:
An alpha channel has these properties:
* Each image (except 16-bit images) can contain up to 24 channels, including all color and alpha channels.
* All channels are 8-bit grayscale images, capable of displaying 256 levels of gray.
* You can specify a name, color, mask option, and opacity for each channel. (The opacity affects the preview of the channel, not the image.)
* All new channels have the same dimensions and number of pixels as the original image.
* You can edit the mask in an alpha channel using painting tools, editing tools, and filters.
* You can convert alpha channels to spot color channels.
One of the things I use alpha channels for is saving selections. You can do this by going to "Select -> Save Selection…", choosing a new channel in the current document and naming it. The saved alpha channel is a mask you can load later when you need to restore the selection. It can be edited, and so on. After saving the selection, you may turn on the alpha channel to see the mask.
Other than that, I’ve not been using alphas in any way, but there are probably many more uses for them…
It also facilitates alpha transparency (partial transparency) in formats like JPG, but I’m no expert in that field. Mike Russell seems to have mentioned it somewhere, tho.
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Branko Vukelic ()