在IOS/Swift中旋转UIImage出现问题

Question

我使用从互联网上下载的扩展程序来旋转 UIImage。 在那里，旋转是可以工作的，但存在一些奇怪的行为。

这是扩展代码：

import UIKit

extension UIImage {

    public func imageRotatedByDegrees(degrees: CGFloat, flip: Bool) -> UIImage {

        let radiansToDegrees: (CGFloat) -> CGFloat = {
            return $0 * (180.0 / CGFloat(M_PI));
        }
        let degreesToRadians: (CGFloat) -> CGFloat = {
            return $0 / 180.0 * CGFloat(M_PI);
        }

        // calculate the size of the rotated view's containing box for our drawing space
        let rotatedViewBox = UIView(frame: CGRect(origin: CGPointZero, size: size));
        let t = CGAffineTransformMakeRotation(degreesToRadians(degrees));
        rotatedViewBox.transform = t;
        let rotatedSize = rotatedViewBox.frame.size

        // Create the bitmap context
        UIGraphicsBeginImageContext(rotatedSize);
        let bitmap = UIGraphicsGetCurrentContext();

        // Move the origin to the middle of the image so we will rotate and scale around the center.
        CGContextTranslateCTM(bitmap, rotatedSize.width / 2.0, rotatedSize.height / 2.0);

        // Rotate the image context
        CGContextRotateCTM(bitmap, degreesToRadians(degrees));

        // Now, draw the rotated/scaled image into the context
        var yFlip: CGFloat;

        if(flip){
            yFlip = CGFloat(-1.0);
        } else {
            yFlip = CGFloat(1.0);
        }

        CGContextScaleCTM(bitmap, yFlip, -1.0);
        CGContextDrawImage(bitmap, CGRectMake(-size.width / 2, -size.height / 2, size.width, size.height), CGImage);

        let newImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();

        return newImage;
    }
}

这是我如何调用扩展方法并将返回的图像设置为图像视图。 图像视图的“contentMode”属性设置为“缩放以填充”

currentPagePreviewImageVew.image = currentPagePreviewImageVew.image!.imageRotatedByDegrees(90, flip: false);

按下旋转按钮之前的图片如下所示：

按下旋转按钮一次后，图片如下所示。（可以看到图片没有旋转，但大小已经改变）

当图像旋转90度时，图片如下所示。（可以看到，当图像处于0和180度时，其他视图会被拉伸，就像上面屏幕（2）中一样）

请问有人能告诉我我的代码有什么问题，如果有更好的解决方案，请让我知道。非常感谢任何帮助。

编辑： 拉伸视图是由于约束问题引起的。我通过在图像视图上方放置一个高度约束来解决了这个问题。但是仍然找不到第一次旋转问题的答案。

- Hanushka Suren

---

@simpleBob 你是怎么完成工作的？ - Hanushka Suren

我从对象上移除并重新设置了约束。 - Daniel

@simpleBob 谢谢，我会试一下。 - Hanushka Suren

@simpleBob 是的，这是一个约束问题。但第一次使用仍然有那个问题。谢谢。 - Hanushka Suren

你修复了这个问题吗？我也遇到了并想要解决。谢谢。 - Libor Zapletal

Answer 1

    func flipImageVertical(originalImage: UIImage) -> UIImage
    {
        let tempImageView:UIImageView = UIImageView(image: originalImage)
        UIGraphicsBeginImageContext(tempImageView.frame.size)
        let context:CGContextRef = UIGraphicsGetCurrentContext()!
        let flipVertical:CGAffineTransform = CGAffineTransformMake(1,0,0,-1,0,tempImageView.frame.size.height)
        CGContextConcatCTM(context, flipVertical)
        tempImageView.layer .renderInContext(context)

        let flippedImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return flippedImage
    }

    func flipImageHorizontal(originalImage: UIImage) -> UIImage
    {
        let tempImageView:UIImageView = UIImageView(image: originalImage)
        UIGraphicsBeginImageContext(tempImageView.frame.size)
        let context:CGContextRef = UIGraphicsGetCurrentContext()!
        let flipHorizontal:CGAffineTransform = CGAffineTransformMake(-1,0,0,1,tempImageView.frame.size.width,0)

        CGContextConcatCTM(context, flipHorizontal)
        tempImageView.layer .renderInContext(context)

        let flippedImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return flippedImage
    }

- Jayesh Miruliya

---

你的两种方法都很好。但这不是我想要的。我想旋转图像，而不是翻转。 - Hanushka Suren

Answer 2

你必须尝试这个：

extension UIImage {
    public func imageRotatedByDegrees(degrees: Double, flip: Bool) -> UIImage {

        // calculate the size of the rotated view's containing box for our drawing space
        let rotatedViewBox = UIView(frame: CGRect(origin: CGPointZero, size: size))
        let t = CGAffineTransformMakeRotation(CGFloat(toRadian(degrees)))
        rotatedViewBox.transform = t
        let rotatedSize = rotatedViewBox.frame.size

        // Create the bitmap context
        UIGraphicsBeginImageContext(rotatedSize)
        let bitmap = UIGraphicsGetCurrentContext()

        CGContextSetAllowsAntialiasing(bitmap, true)
        CGContextSetShouldAntialias(bitmap, true)
        CGContextSetInterpolationQuality(bitmap, CGInterpolationQuality.High)

        // Move the origin to the middle of the image so we will rotate and scale around the center.
        CGContextTranslateCTM(bitmap, rotatedSize.width / 2.0, rotatedSize.height / 2.0)

        //   // Rotate the image context
        CGContextRotateCTM(bitmap, CGFloat(toRadian(degrees)))

        // Now, draw the rotated/scaled image into the context
        var yFlip: CGFloat

        if(flip){
            yFlip = CGFloat(-1.0)
        } else {
            yFlip = CGFloat(1.0)
        }

        CGContextScaleCTM(bitmap, yFlip, -1.0)
        CGContextDrawImage(bitmap, CGRectMake(-size.width / 2, -size.height / 2, size.width, size.height), CGImage)

        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage
    }

然后使用这种方法来满足您的新尺寸：

extension UIImage {
    public func resizeImage(newSize:CGSize) -> UIImage {

        let newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height))
        let imageRef:CGImageRef = self.CGImage!

        UIGraphicsBeginImageContextWithOptions(newSize, false, 0)
        let context:CGContextRef = UIGraphicsGetCurrentContext()!

        // Set the quality level to use when rescaling
        CGContextSetInterpolationQuality(context, CGInterpolationQuality.High)
        CGContextSetAllowsAntialiasing(context, true)
        CGContextSetShouldAntialias(context, true)

        let flipVertical:CGAffineTransform = CGAffineTransformMake(1, 0, 0, -1, 0, newSize.height)

        CGContextConcatCTM(context, flipVertical)
        // Draw into the context; this scales the image
        CGContextDrawImage(context, newRect, imageRef)

        // Get the resized image from the context and a UIImage
        let newImage:UIImage = UIImage(CGImage: CGBitmapContextCreateImage(context)!)

        UIGraphicsEndImageContext();
        return newImage
    }
}

- Alessandro Ornano

---

感谢你的帮助，兄弟。但是这没有解决我的问题。 - Hanushka Suren

Answer 3

我使用了下面的扩展，并且它运行得很好。这实际上是 Swift 3。

import UIKit

extension UIImage {

    public func rotateImageByDegrees(_ degrees: CGFloat) -> UIImage {

        let degreesToRadians: (CGFloat) -> CGFloat = {
            return $0 / 180.0 * CGFloat(M_PI)
        }

        // calculate the size of the rotated view's containing box for our drawing space
        let rotatedViewBox = UIView(frame: CGRect(origin: CGPoint.zero, size: self.size))
        let t = CGAffineTransform(rotationAngle: degreesToRadians(degrees));
        rotatedViewBox.transform = t
        let rotatedSize = rotatedViewBox.frame.size

        // Create the bitmap context
        UIGraphicsBeginImageContext(rotatedSize)
        let bitmap = UIGraphicsGetCurrentContext()

        // Move the origin to the middle of the image so we will rotate and scale around the center.
        bitmap?.translateBy(x: rotatedSize.width / 2.0, y: rotatedSize.height / 2.0);

        // Rotate the image context
        bitmap?.rotate(by: degreesToRadians(degrees));

        // Now, draw the rotated/scaled image into the context
        bitmap?.scaleBy(x: 1.0, y: -1.0)
        bitmap?.draw(self.cgImage!, in: CGRect(x: -self.size.width / 2, y: -self.size.height / 2, width: self.size.width, height: self.size.height))

        let cgimage:CGImage  = bitmap!.makeImage()!
        return UIImage(cgImage: cgimage)
    }
}

其他的事情都和问题中一样。

- Hanushka Suren

---

谢谢你的更新。我以前尝试过类似的方法，但没有帮助，这次也是如此。看起来当我尝试旋转横向照片时，它可以正常工作（即使我将照片先旋转为纵向，再旋转回横向），但如果我把照片拍成纵向，然后尝试旋转 -> 第一次旋转会使图像变形，其他旋转可以正常工作，但会对格式化的照片进行旋转。 - Libor Zapletal

我有一个 UIImageView，那么我该如何使用它？ - MRizwan33

@MRizwan3395：你的意思是你想旋转UIImageView？而不是图像数据？如果你在旋转UIImageView时遇到这样的问题，那肯定是一个约束问题。 - Hanushka Suren