SDWebImage resizing/scaling/cropping images coming from url before caching them - objective-c

Question

How can I resize, scale and crop images coming from url before caching them. I tried to achieve this with the following code.
[cell.profilePicture setImageWithURL:[NSURL URLWithString:[rowData objectForKey:#"pictureUrl"]] placeholderImage:nil];
cell.profilePicture.image = [self imageByScalingAndCroppingForSize:CGSizeMake(cell.profilePicture.frame.size.width, cell.profilePicture.frame.size.height) image:cell.profilePicture.image];
This produced a strange result. First, it shows a not resized/scaled/cropped version. But, when I scroll down and then go back, it shows a resized/scaled/cropped version. I know that this code first caches images and resizes/scales/crops them. But, I could not come up with a better solution. I think there should be something that enables to do downloading images so as to resize/scale/crop and caching independently. Any ideas?
Thank you.

Answer 1

I figured out the solution on my own.
Instead of
[cell.profilePicture setImageWithURL:[NSURL URLWithString:[rowData objectForKey:#"pictureUrl"]] placeholderImage:nil];
which downloads and caches images automatically, use this
SDWebImageManager *manager = [SDWebImageManager sharedManager];
[manager downloadWithURL:url delegate:self options:0 success:^(UIImage *image)
{
cell.profilePicture.image = [self imageByScalingAndCroppingForSize:CGSizeMake(cell.profilePicture.frame.size.width, cell.profilePicture.frame.size.height) image:image];
} failure:nil];
Don't forget to include
#import <SDWebImage/UIImageView+WebCache.h>
#interface YourViewController : UIViewController <SDWebImageManagerDelegate>

Answer 2

If you want to scale UIImage, try this way:
- (void)viewDidLoad {
[super viewDidLoad];
SDWebImageManager *manager = [SDWebImageManager sharedManager];
[manager downloadImageWithURL:[NSURL URLWithString:yourPhotoURL]
options:SDWebImageRefreshCached
progress:nil
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
CGSize size = CGSizeMake(50,50);//width,height
imageView.image = [self imageWithImage:image scaledToSize:size];
}];
}
- (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize{
UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
[image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
imageWithImage method source:The simplest way to resize an UIImage?

Answer 3

This was a great example on how to implement in using SDWebImageManagerDelegate.
#import <Foundation/Foundation.h>
#import <SDWebImage/SDWebImageManager.h>
#interface ImageLoader : NSObject <SDWebImageManagerDelegate>
+ (instancetype)sharedImageLoader;
#end
#implementation ImageLoader
+ (instancetype)sharedImageLoader
{
static ImageLoader* loader = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
loader = [[ImageLoader alloc] init];
});
return loader;
}
- (UIImage *)imageManager:(SDWebImageManager *)imageManager
transformDownloadedImage:(UIImage *)image
withURL:(NSURL *)imageURL
{
// Place your image size here
CGFloat width = 50.0f;
CGFloat height = 50.0f;
CGSize imageSize = CGSizeMake(width, height);
UIGraphicsBeginImageContext(imageSize);
[image drawInRect:CGRectMake(0, 0, width, height)];
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
#end
Then just add the delegate where needed.
[SDWebImageManager sharedManager].delegate = [ImageLoader sharedImageLoader];

Answer 4

If anyone is looking for swift-3 version
self.postImage.sd_setImage(with: URL(string: image)!, placeholderImage: UIImage(named: "image_placeholder"),options: SDWebImageOptions(rawValue: 0),
completed: { (image, error, cacheType, imageURL) in
//Scale or do what ever you want to do to the image
let newImage = self.scaleImage(image: image!, view: self.postImage)
self.postImage.image = newImage
})
func scaleImage(image:UIImage, view:UIImageView) -> UIImage {
let oldWidth = image.size.width
let oldHeight = image.size.height
var scaleFactor:CGFloat
var newHeight:CGFloat
var newWidth:CGFloat
let viewWidth:CGFloat = view.width
if oldWidth > oldHeight {
scaleFactor = oldHeight/oldWidth
newHeight = viewWidth * scaleFactor
newWidth = viewWidth
} else {
scaleFactor = oldHeight/oldWidth
newHeight = viewWidth * scaleFactor
newWidth = viewWidth
}
UIGraphicsBeginImageContext(CGSize(width:newWidth, height:newHeight))
image.draw(in: CGRect(x:0, y:0, width:newWidth, height:newHeight))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage!
}
`