Selection Alpha Channels:
Download the orange basket image to your desktop.
Uncompress the file.
Choose the desktop
Click the file Francisco_de_Zurbaran.jpg
Use the Magnifying Glass to zoom in on the image.
(The option key with the Magnifying Glass zooms out.)
Choose Select->Color Range...
Click on the white background.
Input Expand by: 1 pixel
This will clean up the edge pixels.
Choose Select->Inverse, to select the oranges instead of the background.
Save the selection to an alpha channel.
Choose Select->Save Selection
Choose Windows->Show Channels
Click the fourth channel to bring up the alpha channel, you may want to modify it.
Click the first RGB channel to bring you back to the main image.
You may save as many alpha selection channels as you like.
Choose Select None (This deselects the channel.)
Load the alpha selection channel.
Choose Select->Load Selection
Choose Alpha 1
Choose Edit->Copy (This saves the selected area to a temporary buffer.)
Choose Edit->Paste (Paste the selection into a new layer.)
Choose Windows->Show Layers (Layers is a tab under the Channels tab.)
You can select separate layers to modify.
Notice the top layer has transparency or alpha, this is another alpha channel.
Select the Background Layer from the Layers window.
Hit the Delete Key on the keyboard.
Notice the image fills with the background color in the Tools window.
Select a new color, please notice how this effects the feeling or your perception of the image.
Click the small arrow on the upper right of the Layers window to bring up the menu
Choose Flatten image This will merge the two layers.
You lose the alpha information from the layer.
You still have the alpha information in the Channels window.
If you do not understand the difference ask!