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旋轉 CGImage

[英]Rotating a CGImage

 原文  2012-05-11 03:06:02  2   6    objective-c/ ios/ uiimage/ cgimage

問題描述

我有一個從 UIImagePickerController 獲取的 UIImage。 當我從- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info方法收到圖像時，我將它直接放入 UIImageView 進行預覽，並為用戶提供保存或丟棄圖像的選項。

預覽畫面

當用戶選擇保存選項時，應用程序會獲取圖像的 png 數據並將其保存到它的文檔目錄中。 但是在兩種可能的設備方向之一（僅限橫向）下發生的情況是圖像被顛倒保存（更具體地說，從它應該的位置旋轉 180 度）。 所以當我在圖庫中加載圖像時，它看起來是顛倒的。

（請參閱圖庫中的左下角圖片）

見左下圖

我已經解決了這個問題，UIImagePickerController 中 UIImage 中的原始圖像數據沒有旋轉，而是將方向存儲為對象的一個​​屬性，並且僅在顯示時應用。 所以我試圖使用我在網上找到的一些代碼來旋轉與 UIImage 關聯的 CGImage 。 但它似乎對圖像完全沒有影響。 我使用的代碼如下：

- (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();
}

我想知道為什么這段代碼不起作用，因為我在網上找到的每段代碼都無法進行圖像旋轉。

6 個解決方案

解決方案1
 26 已采納  2012-05-11 08:58:22

-(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;

}

使用這個..它完美無缺！ 確保在從 UIImagePicker 中選取圖像時使用此功能：

例子：

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

確保在從文檔目錄中選擇照片的地方使用此功能。

解決方案2
 10  2015-01-01 12:41:26

旋轉和鏡像 UIImage CGImage 支持數據 - Swift

我最近想更正由CGImage支持的UIImage以匹配所需的方向，而不是依賴 API 來尊重 UIImageOrientation 參數。

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
}

解決方案3
 3  2012-09-11 10:38:49

我有你的問題。你必須使用CGContextTranslateCTM(context, -rotatedSize.width/2, -rotatedSize.height/2);翻譯回上下文CGContextTranslateCTM(context, -rotatedSize.width/2, -rotatedSize.height/2); 以及將繪圖中的矩形原點設置為rotatedViewBox.frame.origin.x,rotatedViewBox.frame.origin.y。 使用此代碼。

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);

解決方案4
 3  2017-04-20 23:24:37

Cameron Lowell Palmer的Swift 3版本回答：

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 colorSpace = imageRef.colorSpace
        let bitmapInfo = imageRef.bitmapInfo

        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

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

        if 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, y: 0, width: originalWidth, height: originalHeight))

            orientedImage = contextRef.makeImage()
        }
    }

    return orientedImage
}

用法：

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

解決方案5
 1  2020-05-14 08:04:03

這只是對先前答案的重構。

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
        }
    }
}

解決方案6
 0  2021-06-17 22:58:45

所有這些答案的問題在於它們具有 UIKit 依賴項。 我正在開發針對 iOS 和 macOS 的 SwiftUI 通用應用程序。 Cameron Lowell Palmer 的回答有一些修改：

  1. bytesPerRow 計算需要在高度和寬度交換后進行，否則 CGImageContext 抱怨 bytesPerRow 不正確

  2. 將 UIImageOrientation 更改為 CGImagePropertyOrientation，並交換左右旋轉的符號

這是我的版本，適用於 iOS 和 macOS：

extension CGImage {
func rotating(to orientation: CGImagePropertyOrientation) -> CGImage? {
    var orientedImage: CGImage?

    let originalWidth = self.width
    let originalHeight = self.height
    let bitsPerComponent = self.bitsPerComponent
    let bitmapInfo = self.bitmapInfo

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

    var degreesToRotate: Double
    var swapWidthHeight: Bool
    var mirrored: Bool

    switch orientation {
    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 bytesPerRow = (width * bitsPerPixel) / 8

    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(self, in: CGRect(x: 0.0, y: 0.0, width: CGFloat(originalWidth), height: CGFloat(originalHeight)))

    orientedImage = contextRef?.makeImage()

    return orientedImage
}

}

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