I want to use the function CGImageSourceCreateThumbnailAtIndex
to create a thumbnail from an UIImage
. All I have is the UIImage
itself. The image is the snapshot on a UIView
.
Please, I don't want to use any other method to create the thumbnail, just the one using CGImageSourceCreateThumbnailAtIndex
, because I want to compare its performance with the other methods I already have.
Said that, this is the code I have so far.
I have create a UIImage
category with this code:
- (UIImage *)createSquaredThumbnailWithWidth:(NSInteger)width {
CFDictionaryRef options = (__bridge CFDictionaryRef) @{
(id) kCGImageSourceCreateThumbnailWithTransform : @YES,
(id) kCGImageSourceCreateThumbnailFromImageAlways : @YES,
(id) kCGImageSourceThumbnailMaxPixelSize : @(width)
};
CGImageRef scaledImageRef = CGImageSourceCreateThumbnailAtIndex(????, 0, options);
UIImage* scaled = [UIImage imageWithCGImage:scaledImageRef];
CGImageRelease(scaledImageRef);
return scaled;
}
My problem is with this line:
CGImageRef scaledImageRef = CGImageSourceCreateThumbnailAtIndex(????, 0, options);
The first parameter of this function demands a CGImageSourceRef
, but like I said, I just have an UIImage
, that image is on memory, not on disk, and I don't want to save it to disk, or the performance will go down the drain.
How do I get a CGImageSourceRef
from a UIImage
that is on memory???
Swift 4 code
let imageData = UIImagePNGRepresentation(image)!
let options = [
kCGImageSourceCreateThumbnailWithTransform: true,
kCGImageSourceCreateThumbnailFromImageAlways: true,
kCGImageSourceThumbnailMaxPixelSize: 300] as CFDictionary
let source = CGImageSourceCreateWithData(imageData, nil)!
let imageReference = CGImageSourceCreateThumbnailAtIndex(source, 0, options)!
let thumbnail = UIImage(cgImage: imageReference)