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Moving Data Between Quartz 2D and Core Image

The Core Image framework is an Objective-C API that supports image processing. Core Image lets you access built-in image filters for both video and still images and provides support for custom filters and near real-time processing. You can apply Core Image filters to Quartz 2D images. For example, you can use Core Image to correct color, distort the geometry of images, blur or sharpen images, and create a transition between images. Core Image also allows you to apply an iterative process to an image—one that feeds back the output of a filter operation to the input. To understand the capabilities of Core Image more fully, see Core Image Programming Guide.

Core Image methods operate on images that are packaged as Core Image images, or CIImage objects. Although “CIImage” looks similar to the “CGImage” on the printed page (or display screen), Core Image does not operate directly on Quartz images (CGImageRef data types). Quartz images must be converted to Core Image images before you apply a Core Image filter to the image.

The Quartz 2D API does not provide any functions that package Quartz images as Core Image images. But Core Image does. The following Core Image methods create a Core Image image from either a Quartz image or a Quartz layer (CGLayerRef). You can use them to move Quartz 2D data to Core Image.

• imageWithCGImage:

• imageWithCGImage:options:

• imageWithCGLayer:

• imageWithCGLayer:options:

The following Core Image methods return a Quartz image from a Core Image image. You can use them to move a processed image back into Quartz 2D:

• createCGImage:fromRect:

• createCGLayerWithSize:info:

For a complete description of Core Image methods, see Core Image Reference Collection.

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