无法分配给属性：“ size”是仅获取属性Swift

Question

I am trying to retrieve an image from URL and I do not know why my image is so huge, I tried to resize my frame but it's of no use. I am thinking to resize my image but it shows

"Cannot assign to property: 'size' is a get-only property"

My code for resizing that I used is:

if let ImageUrl = message.imageUrlLink {

  receivedimg.frame.size = CGSize(width: 150, height: 150)
  receivedimg.image?.size = CGSize(width: 150, height: 150) // error shown here
  self.receivedimg.loadImageUsingCacheWithUrlString(ImageUrl)
}

and the output was

Am I resizing it wrongly?

Answer 1

It is enough to give just size to frame. Important point is that you need to set contentMode of image. When you giv

if let ImageUrl = message.imageUrlLink {
    receivedimg.frame.size = CGSize(width: 150, height: 150)
    receivedimg.image?.contentMode = UIViewContentMode.scaleAspectFit
    self.receivedimg.loadImageUsingCacheWithUrlString(ImageUrl)
} 

From Apple Document;

scaleAspectFit: The option to scale the content to fit the size of the view by maintaining the aspect ratio. Any remaining area of the view's bounds is transparent.

You can check below Apple Document for more information about contentModes:

https://developer.apple.com/documentation/uikit/uiviewcontentmode

Answer 2

Let's look on the UIIMage.size property we'll see:

@property(nonatomic,readonly) CGSize size; // reflects orientation setting. In iOS 4.0 and later, this is measured in points. In 3.x and

and it says read only.

If you want to actually resize the image (and not stretching it for display), you can do something like:

func resizeImageWithAspect(image: UIImage,scaledToMaxWidth width:CGFloat,maxHeight height :CGFloat)->UIImage? {
    let oldWidth = image.size.width;
    let oldHeight = image.size.height;

    let scaleFactor = (oldWidth > oldHeight) ? width / oldWidth : height / oldHeight;

    let newHeight = oldHeight * scaleFactor;
    let newWidth = oldWidth * scaleFactor;
    let newSize = CGSize(width: newWidth, height: newHeight)

    UIGraphicsBeginImageContextWithOptions(newSize,false,UIScreen.main.scale);

    image.draw(in: CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height));
    let newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage
}

use:

let image: UIImage = loadImageFromSomewhere()
myUIImageView.image = resizeImageWithAspect(image: image, scaledToMaxWidth: maxWidth, maxHeight: maxHeight)

There are a lot of other ways to resize the image.