Q: How can I use Uniform Type Identifiers (UTIs) to determine if a given file path is an image file?A: You can determine if a given file, based on its file path, is an image file by comparing its UTI through the Launch Services framework with the supported UTIs from the Image I/O framework. Listing 1: Determining if a file path is an image file.
- (BOOL)isImageFile:(NSString*)filePath
{
BOOL isImageFile = NO;
FSRef fileRef;
Boolean isDirectory;
if (FSPathMakeRef((const UInt8 *)[filePath fileSystemRepresentation], &fileRef, &isDirectory) == noErr)
{
// get the content type (UTI) of this file
CFDictionaryRef values = NULL;
CFStringRef attrs[1] = { kLSItemContentType };
CFArrayRef attrNames = CFArrayCreate(NULL, (const void **)attrs, 1, NULL);
if (LSCopyItemAttributes(&fileRef, kLSRolesViewer, attrNames, &values) == noErr)
{
// verify that this is a file that the Image I/O framework supports
if (values != NULL)
{
CFTypeRef uti = CFDictionaryGetValue(values, kLSItemContentType);
if (uti != NULL)
{
CFArrayRef supportedTypes = CGImageSourceCopyTypeIdentifiers();
CFIndex i, typeCount = CFArrayGetCount(supportedTypes);
for (i = 0; i < typeCount; i++)
{
CFStringRef supportedUTI = CFArrayGetValueAtIndex(supportedTypes, i);
// make sure the supported UTI conforms only to "public.image" (this will skip PDF)
if (UTTypeConformsTo(supportedUTI, CFSTR("public.image")))
{
if (UTTypeConformsTo(uti, supportedUTI))
{
isImageFile = YES;
break;
}
}
}
CFRelease(supportedTypes);
}
CFRelease(values);
}
}
CFRelease(attrNames);
}
return isImageFile;
}
If you require other UTIs not related to image files or ImageIO, in place of CGImageSourceCopyTypeIdentifiers() you may use the following - CFArrayRef UTICreateAllIdentifiersForTag(CFStringRef inTagClass, CFStringRef inTag, CFStringRef inConfirmingToUTI);
Related DocumentationBack to Top  Document Revision History| Date | Notes |
|---|
| 2007-05-11 | First Version |
Posted: 2007-05-11
|
