调整UIImage的大小以适合表格单元格ImageView

Question

I have images of the size 176 points by 176 points. I am trying to resize them so that they fit into a tableViewCell's ImageView. There are a few problems that I am coming across.

Problems

• I don't know what size the image view in the tableViewCell actually is.
• If I simply add the image without resizing it, it is so sharp that it looses detail:
• If I use this extension on UIImage (below), then the transparent parts of the UIImage turn to black, not what I want:

extension UIImage {
    func resizeImageWithBounds(bounds: CGSize) -> UIImage {
        let horizontalRatio = bounds.width/size.width
        let verticalRatio = bounds.height/size.height
        let ratio = max(horizontalRatio, verticalRatio)
        let newSize = CGSize(width: size.width * ratio, height: size.height * ratio)
        UIGraphicsBeginImageContextWithOptions(newSize, true, 0)
        draw(in: CGRect(origin: CGPoint.zero, size: newSize))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage!
    }
}

I am looking for information on how big the UIImageView is and how to best resize an image into it. I really don't want to create another set of assets (I have a lot of images), and I don't think I should have to.

Answer 1

Try changing the contentMode of the cell.

cell.imageView?.contentMode = .scaleAspectFit

Or, if that doesn't work, here's how to fix the issues of your resized images turning black:

UIGraphicsBeginImageContextWithOptions(newSize, false, 0) // <-- changed opaque setting from true to false