Photoshop

Create and edit alpha channel masks

You can create a new alpha channel and then use painting tools, editing tools, and filters to create a mask from the alpha channel. You can also save an existing selection in a Photoshop image as an alpha channel that appears in the Channels palette. See Save and load selections.

Create an alpha channel mask using current options

  1. Click the New Channel button  at the bottom of the Channels palette.
  2. Paint on the new channel to mask out image areas.
    Select areas of the image before you create the channel for the mask. Then paint on the channel to refine the mask.

Create an alpha channel mask and set options

  1. Alt-click (Windows) or Option-click (Mac OS) the New Channel button at the bottom of the Channels palette, or choose New Channel from the Channels palette menu.
  2. Specify options in the New Channel dialog box.
  3. Paint on the new channel to mask out image areas.

Channel options

To change options for an existing channel, double-click the channel thumbnail in the Channels palette.

Options available in the New Channel and Channel Options dialog boxes:

Masked areas
Sets masked areas to black (opaque) and selected areas to white (transparent). Painting with black increases the masked area; painting with white increases the selected area. When this option is selected, the Quick Mask button in the toolbox becomes a white circle on a gray background .

Selected Areas
Sets masked areas to white (transparent) and selected areas to black (opaque). Painting with white increases the masked area; painting with black increases the selected area. When this option is selected, the Quick Mask button in the toolbox becomes a gray circle on a white background 

Spot Color
Converts an alpha channel to a spot color channel. Only available for existing channels.

Color
Sets the color and opacity of the mask. Click the color field to change the color. The color and opacity settings affect only the appearance of the mask and have no effect on how underlying areas are protected. Changing these settings may make the mask more easily visible against the colors in the image.

Paint on a channel to mask image areas

When the new channel appears at the bottom of the Channels palette, it is the only channel visible in the image window. Click the eye icon for the composite color channel (RGB, CMYK) to display the image with a color overlay showing the mask.

 Select the brush or an editing tool and do one of the following to add or subtract from the mask created from the alpha channel:

  • To remove areas in the new channel, paint with white.

  • To add areas in the new channel, paint with black.

  • To add or remove areas using opacities less than 100%, set the opacity in the options bar of the painting or editing tool and then paint with white or black. You can also paint with a color to achieve lower opacities.