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Bitmap Images and Image Masks

Bitmap images and image masks are like any drawing primitive in Quartz. Both images and image masks in Quartz are represented by the CGImageRef data type. As you’ll see later in this chapter, there are a variety of functions that you can use to create an image. Some of them require a data provider or an image source to supply bitmap data. Other functions create an image from an existing image either by copying the image or by applying an operation to the image. No matter how you create a bitmap image in Quartz, you can draw the image to any flavor of graphics context. Keep in mind that a bitmap image is an array of bits at a specific resolution. If you draw a bitmap image to a resolution-independent graphics context (such as a PDF graphics context) the bitmap is limited by the resolution at which you created it.

There is one way to create a Quartz image mask—by calling the function CGImageMaskCreate. You’ll see how to create one in “Creating an Image Mask.” Applying an image mask is not the only way to mask drawing. The sections “Masking an Image With Color,” “Masking an Image With an Image Mask,” and “Masking an Image by Clipping the Context” discuss all the masking methods available in Quartz.

Contents:

About Bitmap Images and Image Masks
Bitmap Image Information
Creating Images
Creating an Image Mask
Masking Images
Using Blend Modes With Images

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