Objective c 旋转CG图像

我有一个从UIImagePickerController获取的UIImage。当我从

-（void）imagePickerController:（UIImagePickerController*）picker通过info:（NSDictionary*）info

方法接收图像时，我将其直接放入UIImageView进行预览，并为用户提供保存或放弃图像的选项

当用户选择保存选项时，应用程序将获取图像的png数据并将其保存到其文档目录中。但是，在两种可能的设备方向之一（仅横向）下发生的情况是，图像被倒置保存（更具体地说，从它应该的位置旋转180度）。因此，当我将图像加载到gallery中时，它看起来是颠倒的

（请参见图库中左下角的图像）

我已经计算出，UIImagePickerController的UIImage中的原始图像数据没有旋转，相反，方向存储为对象上的属性，仅在显示时应用。因此，我尝试使用我在网上找到的一些代码来旋转与UIImage关联的CGImage。但它似乎对图像没有任何影响。我使用的代码如下：

- (void)rotateImage:(UIImage*)image byRadians:(CGFloat)rads
{   
    // calculate the size of the rotated view's containing box for our drawing space 
    UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,image.size.width, image.size.height)];
    CGAffineTransform t = CGAffineTransformMakeRotation(rads);
    rotatedViewBox.transform = t;
    CGSize rotatedSize = rotatedViewBox.frame.size;

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

    // Move the origin to the middle of the image you want to rotate and scale around the center. 
    CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2); 

    // Rotate the image context
    CGContextRotateCTM(bitmap, rads);

    // Now, draw the rotated/scaled image into the context
    CGContextScaleCTM(bitmap, 1.0, -1.0);
    CGContextDrawImage(bitmap, CGRectMake(image.size.width / 2, image.size.height / 2, image.size.width, image.size.height), [image CGImage]);

    image = UIGraphicsGetImageFromCurrentImageContext();
    image = [UIImage imageWithCGImage:image.CGImage scale:1.0 orientation:UIImageOrientationDown];
    UIGraphicsEndImageContext();
}

我想知道为什么这段代码不起作用，因为我在网上找到的每一段进行图像旋转的代码似乎都不起作用

-(UIImage*) rotate:(UIImage*) src andOrientation:(UIImageOrientation)orientation
{
    UIGraphicsBeginImageContext(src.size);

    CGContextRef context=(UIGraphicsGetCurrentContext());

    if (orientation == UIImageOrientationRight) {
        CGContextRotateCTM (context, 90/180*M_PI) ;
    } else if (orientation == UIImageOrientationLeft) {
        CGContextRotateCTM (context, -90/180*M_PI);
    } else if (orientation == UIImageOrientationDown) {
        // NOTHING
    } else if (orientation == UIImageOrientationUp) {
        CGContextRotateCTM (context, 90/180*M_PI);
    }

    [src drawAtPoint:CGPointMake(0, 0)];
    UIImage *img=UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return img;

}

用这个。。它工作完美！从UIImagePicker拾取图像时，请确保使用此功能：

例如：

UIImage *image;
image = [self rotate:image andOrientation:image.imageOrientation];

---

请确保在从文档目录中拾取照片的位置使用此功能。

我遇到了您的问题。您必须使用

CGContextTranslateCTM（context，-rotatedSize.width/2，-rotatedSize.height/2）将上下文翻译回来以及将图形中rect的原点设置为rotatedViewBox.frame.origin.x、rotatedViewBox.frame.origin.y。
使用此代码

UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,image.size.width, image.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation(0.3);
rotatedViewBox.transform = t;
CGSize rotatedSize = rotatedViewBox.frame.size;



UIGraphicsBeginImageContext(rotatedSize);

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, rotatedSize.width/2, rotatedSize.height/2);
CGContextRotateCTM (context, 0.3);
CGContextScaleCTM(context, 1, -1);
CGContextTranslateCTM(context, -rotatedSize.width/2, -rotatedSize.height/2);




CGContextDrawImage(context, CGRectMake(-rotatedViewBox.frame.origin.x, -rotatedViewBox.frame.origin.y, image.size.width, image.size.height), [image CGImage]);


UIImage *nn = UIGraphicsGetImageFromCurrentImageContext();

NSLog(@"size is %f, %f",nn.size.width,nn.size.height);
UIGraphicsEndImageContext();

UIImageWriteToSavedPhotosAlbum(nn, nil,nil,nil);

旋转和镜像UIImage CGImage备份数据-Swift
我最近想更正一个由
CGImage
支持的
UIImage
，以匹配所需的方向，而不是依赖api来遵守UIImageOrientation参数

func createMatchingBackingDataWithImage(imageRef: CGImage?, orienation: UIImageOrientation) -> CGImage?
{
    var orientedImage: CGImage?

    if let imageRef = imageRef {
        let originalWidth = imageRef.width
        let originalHeight = imageRef.height
        let bitsPerComponent = imageRef.bitsPerComponent
        let bytesPerRow = imageRef.bytesPerRow

        let bitmapInfo = imageRef.bitmapInfo

        guard let colorSpace = imageRef.colorSpace else {
            return nil
        }

        var degreesToRotate: Double
        var swapWidthHeight: Bool
        var mirrored: Bool
        switch orienation {
        case .up:
            degreesToRotate = 0.0
            swapWidthHeight = false
            mirrored = false
            break
        case .upMirrored:
            degreesToRotate = 0.0
            swapWidthHeight = false
            mirrored = true
            break
        case .right:
            degreesToRotate = 90.0
            swapWidthHeight = true
            mirrored = false
            break
        case .rightMirrored:
            degreesToRotate = 90.0
            swapWidthHeight = true
            mirrored = true
            break
        case .down:
            degreesToRotate = 180.0
            swapWidthHeight = false
            mirrored = false
            break
        case .downMirrored:
            degreesToRotate = 180.0
            swapWidthHeight = false
            mirrored = true
            break
        case .left:
            degreesToRotate = -90.0
            swapWidthHeight = true
            mirrored = false
            break
        case .leftMirrored:
            degreesToRotate = -90.0
            swapWidthHeight = true
            mirrored = true
            break
        }
        let radians = degreesToRotate * Double.pi / 180.0

        var width: Int
        var height: Int
        if swapWidthHeight {
            width = originalHeight
            height = originalWidth
        } else {
            width = originalWidth
            height = originalHeight
        }

        let contextRef = CGContext(data: nil, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)
        contextRef?.translateBy(x: CGFloat(width) / 2.0, y: CGFloat(height) / 2.0)
        if mirrored {
            contextRef?.scaleBy(x: -1.0, y: 1.0)
        }
        contextRef?.rotate(by: CGFloat(radians))
        if swapWidthHeight {
            contextRef?.translateBy(x: -CGFloat(height) / 2.0, y: -CGFloat(width) / 2.0)
        } else {
            contextRef?.translateBy(x: -CGFloat(width) / 2.0, y: -CGFloat(height) / 2.0)
        }
        contextRef?.draw(imageRef, in: CGRect(x: 0.0, y: 0.0, width: CGFloat(originalWidth), height: CGFloat(originalHeight)))
        orientedImage = contextRef?.makeImage()
    }

    return orientedImage
}

Swift 3版本适用于：

用法：

let newCgImage = createMatchingBackingDataWithImage(imageRef: cgImageRef, orienation: .left)

这只是对前面答案的重构

func correctImageOrientation(cgImage: CGImage?, orienation: UIImage.Orientation) -> CGImage? {
    guard let cgImage = cgImage else { return nil }
    var orientedImage: CGImage?

    let originalWidth = cgImage.width
    let originalHeight = cgImage.height
    let bitsPerComponent = cgImage.bitsPerComponent
    let bytesPerRow = cgImage.bytesPerRow
    let bitmapInfo = cgImage.bitmapInfo

    guard let colorSpace = cgImage.colorSpace else { return nil }

    let degreesToRotate = orienation.getDegree()
    let mirrored = orienation.isMirror()

    var width = originalWidth
    var height = originalHeight

    let radians = degreesToRotate * Double.pi / 180.0
    let swapWidthHeight = Int(degreesToRotate / 90) % 2 != 0

    if swapWidthHeight {
        swap(&width, &height)
    }

    let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)

    context?.translateBy(x: CGFloat(width) / 2.0, y: CGFloat(height) / 2.0)
    if mirrored {
        context?.scaleBy(x: -1.0, y: 1.0)
    }
    context?.rotate(by: CGFloat(radians))
    if swapWidthHeight {
        swap(&width, &height)
    }
    context?.translateBy(x: -CGFloat(width) / 2.0, y: -CGFloat(height) / 2.0)

    context?.draw(cgImage, in: CGRect(x: 0.0, y: 0.0, width: CGFloat(originalWidth), height: CGFloat(originalHeight)))
    orientedImage = context?.makeImage()

    return orientedImage
}

extension UIImage.Orientation {
    func getDegree() -> Double {
        switch self {
        case .up, .upMirrored:
            return 0.0
        case .right, .rightMirrored:
            return 90.0
        case .down, .downMirrored:
            return 180.0
        case .left, .leftMirrored:
            return -90.0
        default:
            return 0
        }
    }

    func isMirror() -> Bool {
        switch self {
        case .up, .right, .down, .left:
            return false
        case .leftMirrored, .upMirrored, .downMirrored, .rightMirrored:
            return true
        default:
            return false
        }
    }
}

很好的回答。。。我唯一要改变的是，“
返回img；
”在“
[img release]；
”（这意味着release调用从未真正命中）之前被调用。此外，这假设此人没有使用弧。你知道为什么旋转是必要的吗？“你正在旋转上下文（及其坐标系），然后将图像绘制到其中。”因此，他们可以将上下文称为画架，对吗？不知道为什么他们没有。理解什么是“画架”（毕竟，大多数人都使用过画架）比理解什么是“背景”更容易。你的解决方案和你的解决方案有什么区别？您正在考虑更多的情况（例如镜像图像）。但还有什么？有些角度似乎不同，使用的方法也不同（
CGContextRotateCTM
vs.
rotate
）。另外，您正在通过

进行翻译，而其他解决方案没有考虑到这一点……还有什么区别？

func correctImageOrientation(cgImage: CGImage?, orienation: UIImage.Orientation) -> CGImage? {
    guard let cgImage = cgImage else { return nil }
    var orientedImage: CGImage?

    let originalWidth = cgImage.width
    let originalHeight = cgImage.height
    let bitsPerComponent = cgImage.bitsPerComponent
    let bytesPerRow = cgImage.bytesPerRow
    let bitmapInfo = cgImage.bitmapInfo

    guard let colorSpace = cgImage.colorSpace else { return nil }

    let degreesToRotate = orienation.getDegree()
    let mirrored = orienation.isMirror()

    var width = originalWidth
    var height = originalHeight

    let radians = degreesToRotate * Double.pi / 180.0
    let swapWidthHeight = Int(degreesToRotate / 90) % 2 != 0

    if swapWidthHeight {
        swap(&width, &height)
    }

    let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)

    context?.translateBy(x: CGFloat(width) / 2.0, y: CGFloat(height) / 2.0)
    if mirrored {
        context?.scaleBy(x: -1.0, y: 1.0)
    }
    context?.rotate(by: CGFloat(radians))
    if swapWidthHeight {
        swap(&width, &height)
    }
    context?.translateBy(x: -CGFloat(width) / 2.0, y: -CGFloat(height) / 2.0)

    context?.draw(cgImage, in: CGRect(x: 0.0, y: 0.0, width: CGFloat(originalWidth), height: CGFloat(originalHeight)))
    orientedImage = context?.makeImage()

    return orientedImage
}

extension UIImage.Orientation {
    func getDegree() -> Double {
        switch self {
        case .up, .upMirrored:
            return 0.0
        case .right, .rightMirrored:
            return 90.0
        case .down, .downMirrored:
            return 180.0
        case .left, .leftMirrored:
            return -90.0
        default:
            return 0
        }
    }

    func isMirror() -> Bool {
        switch self {
        case .up, .right, .down, .left:
            return false
        case .leftMirrored, .upMirrored, .downMirrored, .rightMirrored:
            return true
        default:
            return false
        }
    }
}