Video tutorial: Mask out part of an image

Video tutorial: Mask out part of an image
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About masks and alpha channels

When you select part of an image, the area that is not selected is masked, or protected from editing. So, when you create a mask, you isolate and protect areas of an image as you apply color changes, filters, or other effects to the rest of the image. You can also use masks for complex image editing such as gradually applying color or filter effects to an image.

Photoshop Examples of masks
Examples of masks

A. Opaque mask used to protect the background and edit the butterfly B. Opaque mask used to protect the butterfly and color the background C. Semitransparent mask used to color the background and part of the butterfly 

Masks are stored in alpha channels. Masks and channels are grayscale images, so you can edit them like any other image with painting tools, editing tools, and filters. Areas painted black on a mask are protected, and areas painted white are editable.

Use Quick Mask mode to convert a selection to a temporary mask for easier editing. The Quick Mask appears as a colored overlay with adjustable opacity. You can edit the Quick Mask using any painting tool or modify it with a filter. Once you exit Quick Mask mode, the mask is converted back to a selection on the image.

To save a selection more permanently, you can store it as an alpha channel. The alpha channel stores the selection as an editable grayscale mask in the Channels panel. Once you store the selection as an alpha channel, you can reload it at any time or even load it into another image.

Photoshop Channels panel
Selection saved as an alpha channel in Channels panel

Note:

You can mask or hide parts of a layer using a layer mask.

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 panel. 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 panel.
  2. Paint on the new channel to mask out image areas.

    Note:

    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 panel, or choose New Channel from the Channels panel menu.
  2. Specify options in the New Channel dialog box.
  3. Paint on the new channel to mask out image areas.

Edit channel options

To change options for an existing channel, double-click the channel thumbnail in the Channels panel or select Channel Options from the Channels panel menu.

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 panel, 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.

Save and load selections

You can save any selection as a mask in a new or existing alpha channel and later reload the selection from the mask.

You can use a selection as a layer mask by loading the selection to make it active, then adding a new layer mask.

Save a selection to a new channel

  1. Select the area or areas of the image you want to isolate.
  2. Click the Save Selection button  at the bottom of the Channels panel. A new channel appears, named according to the sequence in which it was created.

Save a selection to a new or existing channel

  1. Use a selection tool to select the area or areas of the image you want to isolate.
  2. Choose Select > Save Selection.
  3. Specify the following in the Save Selection dialog box, and click OK:

    Document

    Chooses a destination image for the selection. By default, the selection is placed in a channel in your active image. You can choose to save the selection to a channel in another open image with the same pixel dimensions or to a new image.

    Channel

    Chooses a destination channel for the selection. By default, the selection is saved in a new channel. You can choose to save the selection to any existing channel in the selected image or to a layer mask if the image contains layers.

  4. If you’re saving the selection as a new channel, type a name for the channel in the Name text box.
  5. If you’re saving the selection to an existing channel, select how to combine the selections:

    Replace Channel

    Replaces the current selection in the channel.

    Add to Channel

    Adds the selection to the current channel contents.

    Subtract From Channel

    Deletes the selection from the channel contents.

    Intersect With Channel

    Keeps the areas of the new selection that intersect with the channel contents.

    You can select the channel from the Channels panel to see the saved selection displayed in grayscale.

Load a saved selection from the Channels panel

You can reuse a previously saved selection by loading it into an image. You can also load the selection into an image after you finish modifying an alpha channel.

  • Do one of the following in the Channels panel:
    • Select the alpha channel, click the Load Selection button  at the bottom of the panel, and then click the composite color channel near the top of the panel.

    • Drag the channel containing the selection you want to load onto the Load Selection button.

    • Ctrl-click (Windows) or Command-click (Mac OS) the channel containing the selection you want to load.

    • To add the mask to an existing selection, press Ctrl+Shift (Windows) or Command+Shift (Mac OS), and click the channel.

    • To subtract the mask from an existing selection, press Ctrl+Alt (Windows) or Command+Option (Mac OS), and click the channel.

    • To load the intersection of the saved selection and an existing selection, press Ctrl+Alt+Shift (Windows) or Command+Option+Shift (Mac OS), and select the channel.

    Note:

    You can drag a selection from one open Photoshop image into another.

Load a saved selection

Note:

If you are loading a saved selection from another image, make sure to open it. Also, make sure your destination image is active.

  1. Choose Select > Load Selection.
  2. Specify the Source options in the Load Selection dialog box:

    Document

    Chooses the source to load.

    Channel

    Chooses the channel containing the selection you want to load.

    Invert

    Selects the non-selected areas.

  3. Select an Operation option to specify how to combine the selections if the image already has a selection:

    New Selection

    Adds the loaded selection.

    Add To Selection

    Adds the loaded selection to any existing selections in the image.

    Subtract From Selection

    Subtracts the loaded selection from existing selections in the image.

    Intersect With Selection

    Saves a selection from an area intersected by the loaded selection and existing selections in the image.

    Note:

    You can drag a selection from one open Photoshop image into another.

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