如何旋转 UIImage

Question

我正在为 iPad 开发一个 iOS 应用程序。有没有办法将 UIImage 旋转 90º，然后将其添加到 UIImageView？我尝试了很多不同的代码，但都没有奏效......

谢谢！

Answer 1

这是 @RyanG 的 Objective C 代码的 swift 版本，作为 UIImage 的扩展：

extension UIImage {

    func rotate(byDegrees degree: Double) -> UIImage {
        let radians = CGFloat(degree*M_PI)/180.0 as CGFloat
        let rotatedViewBox = UIView(frame: CGRect(x: 0, y: 0, width: self.size.width, height: self.size.height))
        let t = CGAffineTransform(rotationAngle: radians)
        rotatedViewBox.transform = t
        let rotatedSize = rotatedViewBox.frame.size
        let scale = UIScreen.main.scale
        UIGraphicsBeginImageContextWithOptions(rotatedSize, false, scale)
        let bitmap = UIGraphicsGetCurrentContext()
        CGContextTranslateCTM(bitmap, rotatedSize.width / 2, rotatedSize.height / 2);

        bitmap!.rotate(by: radians);

        bitmap!.scaleBy(x: 1.0, y: -1.0);
        CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2 , self.size.width, self.size.height), self.CGImage );

        let newImage = UIGraphicsGetImageFromCurrentImageContext()

        return newImage
    }

}

用法是image.rotate(degree)。

Answer 2

当我想改变图像的方向（顺时针旋转 90 度）时，这就是我所做的。

//Checking for the orientation ie, image taken from camera is in portrait or not.
if(yourImage.imageOrientation==3)
{
    //Image is in portrait mode.
    yourImage=[self imageToRotate:yourImage RotatedByDegrees:90.0];
}

- (UIImage *)image:(UIImage *)imageToRotate RotatedByDegrees:(CGFloat)degrees
{
    CGFloat radians = degrees * (M_PI / 180.0);

    UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0, image.size.height, image.size.width)];
    CGAffineTransform t = CGAffineTransformMakeRotation(radians);
    rotatedViewBox.transform = t;
    CGSize rotatedSize = rotatedViewBox.frame.size;

    UIGraphicsBeginImageContextWithOptions(rotatedSize, NO, [[UIScreen mainScreen] scale]);
    CGContextRef bitmap = UIGraphicsGetCurrentContext();

    CGContextTranslateCTM(bitmap, rotatedSize.height / 2, rotatedSize.width / 2);

    CGContextRotateCTM(bitmap, radians);

    CGContextScaleCTM(bitmap, 1.0, -1.0);
    CGContextDrawImage(bitmap, CGRectMake(-image.size.width / 2, -image.size.height / 2 , image.size.height, image.size.width), image.CGImage );
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage;
}

旋转后的图像大小可能 >= 15MB（根据我的经验）。所以你应该压缩它并使用它。否则，您可能会遇到导致内存压力的崩溃。下面给出了我用于压缩的代码。

NSData *imageData = UIImageJPEGRepresentation(yourImage, 1);
//1 - it represents the quality of the image.
NSLog(@"Size of Image(bytes):%d",[imageData length]);
//Here I used a loop because my requirement was, the image size should be <= 4MB.
//So put an iteration for more than 1 time upto when the image size is gets <= 4MB.
for(int loop=0;loop<100;loop++)
{
    if([imageData length]>=4194304)  //4194304 = 4MB in bytes.
    {
        imageData=UIImageJPEGRepresentation(yourImage, 0.3);
        yourImage=[[UIImage alloc]initWithData:imageData];
    }
    else
    {
        NSLog(@"%d time(s) compressed.",loop);
        break;
    }
}

现在您的yourImage 可以在任何地方使用.. 编码愉快...

Answer 3

UIImage *img = [UIImage imageWithName@"aaa.png"];
UIImage *image = [UIImage imageWithCGImage:img.CGImage scale:1.0 orientation:UIImageOrientationRight];

Answer 4

感谢 Jason Crocker，这解决了我的问题。只进行了一次小的修正，两个位置的高度和宽度互换，不会发生变形，即，

UIGraphicsBeginImageContext(CGSizeMake(size.width, size.height));
[[UIImage imageWithCGImage:[sourceImage CGImage] scale:1.0 orientation:clockwise ? UIImageOrientationRight : UIImageOrientationLeft]  drawInRect:CGRectMake(0,0,size.width,size.height)]; 

CGContextRotateCTM 无法解决我的问题，我不知道为什么。我的问题是我正在将我的图像传输到服务器并且它总是显示为 90 度。您可以通过将图像复制到您在 Mac 上运行的 MS Office 程序来轻松测试您的图像是否可以在非苹果世界中工作。

Answer 5

这会将图像旋转任意给定的度数。

请注意，这也适用于 2x 和 3x 视网膜

- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees {
    CGFloat radians = DegreesToRadians(degrees);

    UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0, self.size.width, self.size.height)];
    CGAffineTransform t = CGAffineTransformMakeRotation(radians);
    rotatedViewBox.transform = t;
    CGSize rotatedSize = rotatedViewBox.frame.size;

    UIGraphicsBeginImageContextWithOptions(rotatedSize, NO, [[UIScreen mainScreen] scale]);
    CGContextRef bitmap = UIGraphicsGetCurrentContext();

    CGContextTranslateCTM(bitmap, rotatedSize.width / 2, rotatedSize.height / 2);

    CGContextRotateCTM(bitmap, radians);

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

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage;
}

Answer 6

使用 Swift，您可以通过以下方式旋转图像：

var image: UIImage = UIImage(named: "headerBack.png")
var imageRotated: UIImage = UIImage(CGImage: image.CGImage, scale:1, orientation: UIImageOrientation.UpMirrored)

Answer 7

如果你想旋转UIImage而不是UIImageView，还有imageWithCIImage:scale:orientation

具有以下方向之一：

typedef enum {
   UIImageOrientationUp,
   UIImageOrientationDown,   // 180 deg rotation
   UIImageOrientationLeft,   // 90 deg CW
   UIImageOrientationRight,   // 90 deg CCW
   UIImageOrientationUpMirrored,    // vertical flip
   UIImageOrientationDownMirrored,  // horizontal flip
   UIImageOrientationLeftMirrored,  // 90 deg CW then perform horizontal flip
   UIImageOrientationRightMirrored, // 90 deg CCW then perform vertical flip
} UIImageOrientation;

Answer 8

要旋转像素，您可以使用以下方法。这将创建一个带有旋转元数据的中间 UIImage，并将其渲染到一个宽度/高度尺寸转置的图像上下文中。生成的图像具有旋转的像素（即底层 CGImage）

- (UIImage*)rotateUIImage:(UIImage*)sourceImage clockwise:(BOOL)clockwise
{
    CGSize size = sourceImage.size;
    UIGraphicsBeginImageContext(CGSizeMake(size.height, size.width));
    [[UIImage imageWithCGImage:[sourceImage CGImage] scale:1.0 orientation:clockwise ? UIImageOrientationRight : UIImageOrientationLeft] drawInRect:CGRectMake(0,0,size.height ,size.width)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage;
}

还有其他可能的值可以传递给方向参数以实现 180 度旋转和翻转等。

Answer 9

另一种方法是使用 Core Graphics 再次渲染 UIImage。

获得上下文后，使用CGContextRotateCTM。

更多信息on this Apple Doc

Answer 10

您可以旋转UIImageView 本身：

UIImageView *iv = [[UIImageView alloc] initWithImage:image];
iv.transform = CGAffineTransformMakeRotation(M_PI_2);

或者如果你真的想改变图像，你可以使用this answer的代码，它可以工作。