Joomla End User Tutorials
Photoshop Tutorials : Channel Mask
In this tutorial we will create a channel mask and define a custom shape. We will start with an image that has a selection area created with the Quick Mask tool.
download the custom shape here ›
This is the image we will use for this tutorial. We will start with a Quick Mask which we have already prepared.
Swap from the quick mask mode to standard mode. You should now have your cutout area selected.
Next click on the Channels tab in your Layers palette. You will see four channels there (RGB, Red, Green, & Blue).
Add a new channel by clicking on the "Create a new Channel" button located at the bottom of your layers palette. (This will turn your image to black)
Now select the new channel and fill your selection area with white (You can use the paintbrush tool, or the paintbucket tool). then press ctrl-D to deselect your image You now have an alpha channel that can be used to load a selection whenever you wish. But lets take this area and clean it up so we can create a custom shape.
Alpha channels use a range of colors from white to black, white being fully selected, black being deselected and shades of gray to create an opacity selection of varying degrees. Be sure to clean up your selection area by painting fuzzy areas, you don't want selected, black.
You should now have something that looks like this. ›
Now, to clean up the edges of your selection.
Click Filter › Gaussian Blur. Set the blur to a level that smoothes out the jagged edges of you selection (usually about 3 0r 4).
You can now turn on the RGB channel(click the box to it's left to make it visible) This will allow you to edit the Alpha channel the same way you edit a quick mask.
Now click Image › Adjustments › Levels and slide the outside triangles towards the middle, until your edges are sharp, and line up with the edges of the origional image.
Now that the selection area is cleaned up, click on the Paths tab in the layers palette. Click Select › Load Selection, and use the drop down menu to select the alpha channel you just created.
Now click the "Make Work Path" button at the bottom of the palette and set the tolerance to 1. This will create a work path along your selection area.
Now that you have a path, click Edit › Define Custom Shape. Be sure to save your shapes in the custom shapes palette so you can use it at a later date.
You should now have a new vector shape that can be used via the Custom Shape Tool on your toolbar. Which allows you to create a shape that looks like this ›