Another masking technique utilizes the transparency of the object (in an image) itself to affect its visibility. This can help you to edit your old images and give them a new look. You can also play around with your new images and create something unique that can be used in advertising, social networking or just for creating a photo album. For masking an object, you can either use a vector or a bitmap image. The technique can be applied to multiple objects or grouped objects as well. Often, business professionals use masking for creating catalogues for various products that they sell.

If you have used other vector illustration applications such as Macromedia FreeHand, perhaps you are familiar with vector masks, which are very convenient for image editing. The layout of a vector mask object crops the underlying objects to the shape of its path, creating a cookie-cutter effect. When a vector mask is created, the Layers panel displays a thumbnail with a pen icon to indicate that it has created a mask of this type. Not only that, you also get the option to customize the color of the masked object and give it a different style altogether.

If you have used Photoshop you are probably familiar with layer masks. Bitmap masking resemble the layer in which the pixels in the image affect the visibility of underlying objects. This technique can be applied in two different ways:

• By using an existing object to hide other objects – This technique is similar to the way vector masking is applied.
• By creating what is called an empty mask – Empty, fully transparent or totally opaque masks can help in highlighting or hiding objects in an image. A transparent (or white) mask highlights all the masked objects, while an opaque (or black) mask hides them.