CGImageSourceCreateWithURL returns always NULL - objective-c

Question

I need to read the properties of an image without load or download it. In fact i have implemented a simple method that use the CGImageSourceCreateWithUrl for accomplish this.
My problem is that it is returning always error because seems that the imageSource is null. So what can i do for fix it?
In the NSURL object i pass urls like:
"http://www.example.com/wp-content/uploads/image.jpg" but also ALAssets library Id used to retrieve images inside the phone like "assets-library://asset/asset.JPG?id=E5F41458-962D-47DD-B5EF-E606E2A8AC7A&ext=JPG".
This is my method:
-(NSString *) getPhotoInfo:(NSString *)paths{
NSString *xmlList = #“test”;
NSURL * imageFileURL = [NSURL fileURLWithPath:paths];
NSLog(#"imageFileURL %#", imageFileURL);
CGImageSourceRef imageSource = CGImageSourceCreateWithURL((__bridge CFURLRef)(imageFileURL), NULL);
if (imageSource == NULL) {
// Error loading image
NSLog(#"Error loading image");
}
CGFloat width = 0.0f, height = 0.0f;
CFDictionaryRef imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, NULL);
NSLog(#"image source %#", imageSource);
return xmlList;
}
I have saw this posts for try to fix it but nothing seems working:
CGImageSourceRef imageSource = CGImageSourceCreateWithURL returns NULL
CGImageSourceCreateWithURL with authentication
accessing UIImage properties without loading in memory the image
In my project ARC is enabled.
Thanks

Answer 1

If you are passing the string "http://www.example.com/wp-content/uploads/image.jpg” to -fileURLWithPath: it’s going to return nil, because that string is sure not a file path, it’s a URL string.
Think of -fileURLWithPath: as just prepending the string you pass in with “file://localhost/“...so you’d end up with a URL that looks like "file://localhost/http://www.example.com/wp-content/uploads/image.jpg”. That’s not good.
You need to call [NSURL URLWithString:paths] if you’re going to be passing in entire URL strings, not just a filesystem path strings.

Answer 2

Working with "assets-library://asset/asset.JPG?id.........., try this code
-(UIImage*)resizeImageToMaxSize:(CGFloat)max anImage:(UIImage*)anImage
{
NSData * imgData = UIImageJPEGRepresentation(anImage, 1);
CGImageSourceRef imageSource = CGImageSourceCreateWithData((CFDataRef)imgData, NULL);
if (!imageSource)
return nil;
CFDictionaryRef options = (CFDictionaryRef)[NSDictionary dictionaryWithObjectsAndKeys:
(id)kCFBooleanTrue, (id)kCGImageSourceCreateThumbnailWithTransform,
(id)kCFBooleanTrue, (id)kCGImageSourceCreateThumbnailFromImageIfAbsent,
(id)[NSNumber numberWithFloat:max], (id)kCGImageSourceThumbnailMaxPixelSize,
nil];
CGImageRef imgRef = CGImageSourceCreateThumbnailAtIndex(imageSource, 0, options);
UIImage* scaled = [UIImage imageWithCGImage:imgRef];
//these lines might be skipped for ARC enabled
CGImageRelease(imgRef);
CFRelease(imageSource);
return scaled; }