Adobe Photoshop Tutorial. Copyright Michael B. Karbo.
11. Alpha channels
We presume that you now have a rather perfect mask of the dear little fellow. A masking is fine – but it is sensitive. If you just once click in it with a tool, it is lost. So it is important tobe able to save a selection.
Make an alpha-channel
1. You have the selection on the screen. Aktivate the Channels palette (behind Layers). Then click on this small button in the bottom of the palette:
2. That creates a new channel, which is seen as a beam. The channel makes a clear teddy bear mask:
3. The save the picture. Now the mask is saved also, and this means that the selection can be recreated later.
4. Close the image file with Control+w.
Pure teddy bear with feathering
Now we need to remove the background.
1. Start by reopening the image file. Select menu items File --> Open Recent, and choose the peter plys.psd file:
2. Now you will see that the selection is saved. Open the Channels palette again:
3. Hold the Control key down and click once on the channel Alpha 1. Then the selection is read in, as seen in the picture again:
4. Now the selection needs a slight feathering. That will give a soft transition to the coming new background. Choose menu items Select --> Feather, and enter Feather Radius 1:
5. Click OK; You can not see anything happening, the teddy bear is still selected.
6. Now you need to invert the selection, so the background will be selected in stead. Try the shortcut Control+Shift-+i for that.
7. Press Delete; then everything else (that is the background) but the teddy bear is removed.
8. Cancel the selection with Control+d, and save the image file.