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Alpha channel

(Last update: 11-2002)

Using Photoshop to apply Alpha Channels in TIFFS

I'm using Photoshop 3.0 for this, because for all other things I use Paint Shop Pro 7.

Step 1

Imagine you want the above TIFF with transparent parts. I used black for the transparent parts, but you can choose any color.

Step 2

If you start up Photoshop you will find a menu like this somewhere on your desktop. Choose the channels tab and push the button.

Step 3

A fifth row will appear. Click this row and your picture will turn entirely in white or black. Don't worry, nothing's lost.
If this picture is not white, but black make it white using the floodfill tool.

Step 4

Go back to the uppermost (RGB) row and click it. Your picture will be back. Use the magic wand tool to select an black area.

Step 5

Go back to the bottom row, click it and you will see the shape selected in this channel, too. Use from the main menu edit/fill and choose black as fill color.

Step 6

Now remember; Every area wich is black in the bottom channel, will be transparent, regardless of the color in the RGB channel. Everything wich is white is not transparent. Grey makes an area half-transparent; light grey less transparent then dark grey. If you use grey, the RGB picture will be half visible. Remember you don't need to use plain colors in the alpha channel. You can use a grey-shade texture as well to get special effects..

example 1

This is the final alpha channel for the grating

example 2

This is an alpha channel for a scrn2, a broken window.

example 3

This is the alpha channel of the filthy front screen of the Diamond T

Have fun