SDWebImage process images before caching

Question

I fetch a lot of images from the web, and they are all kind of sizes - they can be big, small etc..

So I can resize them when I display them in the cell but this is inefficient. It's way better to resize them after SDWebImage have download them and cache them resized, instead of storing large images on disk and resize them for every cell.

So how can I do this with SDWebImage, or I have to hack a bit onto the class?

Answer 1

I had the same problem as you, and tried tweaking SDWebImage first, but ended up building my own component that solved the problem. You can take take a look at it here : https://github.com/adig/RemoteImageView

Answer 2

SDWebImage developer Olivier Poitrey answered this question for me here.

You have to implement the SDWebImageManagerDelegate protocol and then set it as the shared manager's delegate like this:

SDWebImageManager.sharedManager.delegate = self;

using the imageManager:transformDownloadedImage:withURL: instance method.

More information.

Worked perfectly for me.

Answer 3

SDWebImage 3.8.2

If using UIImageView category sd_setImageWithURL. I have created another UIImageView category (extension)

func modifiedImageFromUrl(url: NSURL?) {
    self.sd_setImageWithURL(url) { (image, error, cacheType, url) in
        if cacheType == SDImageCacheType.None && image != nil {
            dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)) {
                let modifiedImage = // modify image as you want

                dispatch_async(dispatch_get_main_queue()) {
                    SDWebImageManager.sharedManager().saveImageToCache(modifiedImage, forURL: url)

                    self.image = modifiedImage
                }
            }
        }
    }
}

Answer 4

Expansion on MaeSTRo's answer in Swift 3:

myImageView.sd_setImage(with: imageUrl){ (image, error, cacheType, url) in
    guard let image = image, cacheType == .none else { return }

    DispatchQueue.global(qos: .userInitiated).async {
        let modifiedImage = myImageProcessor(image)
        SDWebImageManager.shared().saveImage(toCache: modifiedImage, for: imageUrl)
        DispatchQueue.main.async {
            myImageView.image = modifiedImage
            myImageView.setNeedsDisplay()
        }
    }
}