As discussed above, a channel can be thought of as an individual band or separation of image information. The intriguing aspect of this is that the information stored in a channel does not necessarily have to be colour or brightness information. As a matter of fact, you can store selection or mask information on a channel if you wish.

 

To do this, make a selection with any of the selection tools, and then choose Select->Save Selection from the menu bar. You will then see the following dialog box.

 

 

In this box, you can enter a name for your selection, and when you click OK it will be added as a new additional channel along with the other channels in your image.

 

 

Here is the channels palette after saving a selection to a new channel.

 

 

You can also make a selection on the image, and then save it to a new channel by clicking the save selection icon at the bottom of the channels palette.

 

 

If you already have a selection saved as a channel, you can make another selection on your image, and then once again choose Select->Save Channel to display the save selection dialog.

 

 

This time, if you use the drop list labelled Channel, to choose the selection option over the default new option, you will enable a series of radio buttons from which you can choose.

 

If you select the replace channel radio button, the previously created channel will be replaced with a new one containing the new selection.

If you select add to channel, the most recent selection will be added to the channel containing the first selection.

If you select subtract from channel, your current selection will be subtracted from the selection saved on the channel.

Finally, if you select intersect with channel, the overlapping areas of the selections will be saved in the channel.

 

In this channels palette, you can see two selections saved in the same selection channel at the bottom.

 

 

This was accomplished by choosing the Add to Channel radio button when saving the second selection. You can save multiple selections on one channel or on different channels if you wish.

To load a saved selection, choose Select->Load Selection from the menu bar. This will display the Load Selection Dialog.

 

 

You can choose which selection to load from the drop list labelled Channel. Once you have made your choice, click OK to load the saved selection.