如何合并两个UIImages并保持纵横比和大小？

Question

代码已经添加到Github，以便让您了解实际问题。

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这是层次结构：

-- ViewController.View P [width: 375, height: 667]
---- UIImageView A       [width: 375, height: 667] Name: imgBackground
                         [A is holding an image of size(1287,1662)]
---- UIImageView B       [width: 100, height: 100] Name: imgForeground
                         [B is holding an image of size(2400,982)]

我正在尝试将A与B合并，但结果被拉伸了。

这是合并代码：

func mixImagesWith(frontImage:UIImage?, backgroundImage: UIImage?, atPoint point:CGPoint, ofSize signatureSize:CGSize) -> UIImage {
    let size = self.imgBackground.frame.size
    UIGraphicsBeginImageContextWithOptions(size, false, UIScreen.main.scale)
    backgroundImage?.draw(in: CGRect.init(x: 0, y: 0, width: size.width, height: size.height))
    frontImage?.draw(in: CGRect.init(x: point.x, y: point.y, width: signatureSize.width, height: signatureSize.height))
    let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()
    return newImage
}

注意:

• .contentMode = .scaleAspectFit
• 代码可以工作但结果被拉伸了。
• 请看代码中的这一行，let size = self.imgBackground.frame.size - 我需要更改此行以解决问题。找到子视图相对于UIImage大小的原点

以下是用于理解问题的屏幕截图:

我应该怎么做才能正确使用合并函数？

- Hemang

Answer 1

尝试下面的代码，它对我有效，希望对你也有效。

func addWaterMarkToImage(img:UIImage, sizeWaterMark:CGRect, waterMarkImage:UIImage, completion : ((UIImage)->())?){
     handler = completion
    let img2:UIImage = waterMarkImage
    let rect = CGRect(x: 0, y: 0, width: img.size.width, height: img.size.height)
    UIGraphicsBeginImageContext(img.size)
    img.draw(in: rect)
    let frameAspect:CGRect = getAspectFitFrame(sizeImgView: sizeWaterMark.size, sizeImage: waterMarkImage.size)
    let frameOrig:CGRect = CGRect(x: sizeWaterMark.origin.x+frameAspect.origin.x, y: sizeWaterMark.origin.y+frameAspect.origin.y, width: frameAspect.size.width, height: frameAspect.size.height)
    img2.draw(in: frameOrig, blendMode: .normal, alpha: 1)

    let result = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    if handler != nil {
        handler!(result!)
    }
}
//MARK - Get Aspect Fit frame of UIImage
func getAspectFitFrame(sizeImgView:CGSize, sizeImage:CGSize) -> CGRect{

    let imageSize:CGSize  = sizeImage
    let viewSize:CGSize = sizeImgView

    let hfactor : CGFloat = imageSize.width/viewSize.width
    let vfactor : CGFloat = imageSize.height/viewSize.height

    let factor : CGFloat = max(hfactor, vfactor)

    // Divide the size by the greater of the vertical or horizontal shrinkage factor
    let newWidth : CGFloat = imageSize.width / factor
    let newHeight : CGFloat = imageSize.height / factor

    var x:CGFloat = 0.0
    var y:CGFloat = 0.0
    if newWidth > newHeight{
        y = (sizeImgView.height - newHeight)/2
    }
    if newHeight > newWidth{
        x = (sizeImgView.width - newWidth)/2
    }
    let newRect:CGRect = CGRect(x: x, y: y, width: newWidth, height: newHeight)

    return newRect

}

- Patel Jigar

Answer 2

你的代码有两个bug：

1. You should also calculate aspect for document image to fit it into UIImageView. In mergeImages() replace:

   img.draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
   

   with:

   img.draw(in: getAspectFitFrame(sizeImgView: size, sizeImage: img.size))
   

2. When calculating aspect you center image horizontally/vertically if its width/height less then UIImageView width/height. But instead of comparing newWidth and newHeight you should compare factors:

   if hfactor > vfactor {
       y = (sizeImgView.height - newHeight) / 2
   } else {
       x = (sizeImgView.width - newWidth) / 2
   }
   

- mixel

---

嗨，Michael，感谢你的回答。这里有一个小问题。由于两个图像的大小不同，在合并后，UIImage B 的原点变化明显。我该怎么做才能获得相对于原始图像大小（即 UIImage A）的确切原点？ - Hemang

@Hemang 我在不同的模拟器上进行了测试，使用你提供的源代码合并后，我没有看到任何起源变化。你可以另外提一个问题吗？ - mixel

谢谢，Michael，这是新的问题。 - Hemang