Using the Image I/O Framework in Your Application

Image I/O resides in the Application Services framework in OS X, and in the Image I/O framework in iOS. After adding the framework to your application, import the header file by including this statement:

#import <ImageIO/ImageIO.h>

Supported Image Formats

The Image I/O framework understands most of the common image file formats, such as JPEG, JPEG2000, RAW, TIFF, BMP, and PNG. Not all formats are supported on each platform. For the most up-to-date list of what Image I/O supports, you can call the these functions:

• CGImageSourceCopyTypeIdentifiers returns an array of the Uniform Type Identifiers (UTIs) that Image I/O supports as image sources.

• CGImageDestinationCopyTypeIdentifiers returns an array of the uniform type identifiers (UTIs) that Image I/O supports as image destinations.

You can then use the CFShow function to print the array to the debugger console in Xcode, as shown in Listing 1-1. The strings in the array returned by these functions take the form of com.apple.pict, public.jpeg, public.tiff, and so on. Table 1-1 lists the UTIs for many common image file formats. OS X and iOS define constants for most common image file formats; The full set of constants are declared in the UTCoreTypes.h header file. You can use these constants when you need to specify an image type, either as a hint for an image source (kCGImageSourceTypeIdentifierHint) or as an image type for an image destination.

Listing 1-1  Getting and printing supported UTIs

CFArrayRef mySourceTypes = CGImageSourceCopyTypeIdentifiers();

CFShow(mySourceTypes);

CFArrayRef myDestinationTypes = CGImageDestinationCopyTypeIdentifiers();

CFShow(myDestinationTypes);