目标：裁减UI
Image(以2.0的比例属性开始)
我执行以下代码：
let croppedCGImage = originalUIImage.cgImage!.cropping(to: cropRect) let croppedUIImage = UIImage(cgImage: croppedCGImage!)
这段代码工作,但是结果,croppedUllmage,具有不正确的scale属性1.0.
创建最终图像时,我已经尝试指定了缩放比例：
let croppedUIImage = UIImage(cgImage: croppedCGImage!,scale: 2.0,orientation: .up)
这产生正确的比例,但是它将尺寸尺寸减半地不正确.
我该怎么办？
(*注意：UIImage上的scale属性很重要,因为我稍后用受尺度属性影响的UIImagePNGRepresentation(_ image：UIImage)保存图像)
编辑：
我得到以下工作.不幸的是,它比CGImage裁剪功能慢得多.
extension UIImage {
func cropping(to rect: CGRect) -> UIImage {
UIGraphicsBeginImageContextWithOptions(rect.size,false,self.scale)
self.draw(in: CGRect(x: -rect.origin.x,y: -rect.origin.y,width: self.size.width,height: self.size.height))
let croppedImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return croppedImage
}
}
解决方法
尝试这个：
extension UIImage {
func imageByCropToRect(rect:CGRect,scale:Bool) -> UIImage {
var rect = rect
var scaleFactor: CGFloat = 1.0
if scale {
scaleFactor = self.scale
rect.origin.x *= scaleFactor
rect.origin.y *= scaleFactor
rect.size.width *= scaleFactor
rect.size.height *= scaleFactor
}
var image: UIImage? = nil;
if rect.size.width > 0 && rect.size.height > 0 {
let imageRef = self.cgImage!.cropping(to: rect)
image = UIImage(cgImage: imageRef!,scale: scaleFactor,orientation: self.imageOrientation)
}
return image!
}
}
