Tuesday, February 8, 2011

Tips: How to create and edit alpha channel masks in Photoshop

In this article, let’s discuss about creating a new alpha channel and then using the paint tools, editing tools and the filters to create a mask from the alpha channel. Moreover, you can also save an existing selection in an Adobe Photoshop image as an alpha channel that appears in the Channels Panel. Now, follow the steps provided below to create an alpha channel mask using the current options.
•    First, it is required to click the New Channel button at the bottom of the Channels Panel.
•    Then, paint on the new channel to mask out the image areas.
•    After that, it is required to select areas of the image before you create the channel for the mask.
•    Now, you can paint on the channel to refine the mask.
Now, let’s try creating an alpha channel mask and set options
•    It is required to Alt-click (Windows) or Option-click (Mac OS) the New Channel button at the bottom of the Channels panel, or choose New Channel from the Channels panel menu.
•    Then, specify options in the New Channel dialog box.
•    After that, paint on the new channel to mask out image areas.

In this area, we are going to discuss about the channel options.
If you wish to change the options for an existing channel, it is required to double click the channel thumbnail in the Channels Panel or select Channel Options from the Channels Panel menu.
Okay, Fine!!! Now, let’s discuss about the options available in the New Channel and Channel Options dialog boxes.
Masked areas
This 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. If this option is selected, the Quick Mask button in the toolbox becomes a white circle on a grey background.
Selected Areas
This sets masked areas to white (Transparent) and selected areas to black (Opaque). This is just opposite to Masked Areas. If you paint with white, it will increase the masked area and if you paint with white, it will increase the selected area. If this option is selected, the Quick Mask button in the toolbox will become a white circle on the grey background.

Spot Color
This converts an alpha channel to a spot color channel. This is available only for existing channels.
Color
This is used to set the color and opacity of the mask. If you wish to change the color, it is required to click the color field. The color and opacity settings affect only the appearance of the mask and have no effect on how underlying areas are protected. However, changing these settings may make the mask more easily visible against the colors in the image.

Paint on a channel to mask image areas
This section is about paint on a channel to mask image areas.
If the new channel appears at the bottom of the Channels Panel, it is the only channel visible in the image window. You can click on the eye icon for the composite color channel (RGB, CMYK) to display the image with a color overlay showing the mask.
Then, you can select the brush or an editing tool to do any of the following in order to subtract from the mask created from the alpha channel.
•    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.
•    To remove areas in the new channel, paint with white.
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