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Working With Bitmap Image Data

A Quartz image (CGImageRef data type) is an abstract representation of a bitmap image that encapsulates image data together with information about how to interpret and draw the data. A Quartz image is immutable—that is, you cannot “draw into” a Quartz image or change its attributes. You use Quartz images to work with bitmap data in a device-independent manner while taking advantage of built-in Quartz features such as color management, anti-aliasing, and interpolation.

This chapter provides strategies for performing the following tasks:

• “Moving Bits to the Screen” outlines the functions you can use to move bits, should you really need to do so.

• “Getting Image Data and Creating an Image” discusses strategies for obtaining bitmap image data.

• “Changing Pixel Depth” discusses why changing pixel depth is not an issue in Quartz.

• “Drawing Subimages” shows a variety of ways that you can use Quartz to draw a portion of an image.

• “Resizing Images” gives information on changing the size or scaling of an image.

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