從旋轉的UIImageView創建UIImage

Question

我有一個UIImageView和一個圖像。我通過將UIImageView的transform屬性設置爲CGAffineTransformMakeRotation（angle）（其中angle是以弧度表示的角度）來旋轉圖像。

我希望能夠創建另一個UIImage，它對應於我在我看來可以看到的旋轉版本。

我幾乎沒有，通過旋轉圖像方面，我得到一個旋轉的圖像：

- (UIImage *) rotatedImageFromImageView: (UIImageView *) imageView 
{ 
    UIImage *rotatedImage; 

    // Get image width, height of the bounding rectangle 
    CGRect boundingRect = [self getBoundingRectAfterRotation: imageView.bounds byAngle:angle]; 

    // Create a graphics context the size of the bounding rectangle 
    UIGraphicsBeginImageContext(boundingRect.size); 
    CGContextRef context = UIGraphicsGetCurrentContext(); 

    // Rotate and translate the context 
    CGAffineTransform ourTransform = CGAffineTransformIdentity; 
    ourTransform = CGAffineTransformConcat(ourTransform, CGAffineTransformMakeRotation(angle)); 

    CGContextConcatCTM(context, ourTransform); 

    // Draw the image into the context 
    CGContextDrawImage(context, CGRectMake(0, 0, imageView.image.size.width, imageView.image.size.height), imageView.image.CGImage); 

    // Get an image from the context 
    rotatedImage = [UIImage imageWithCGImage: CGBitmapContextCreateImage(context)]; 

    // Clean up 
    UIGraphicsEndImageContext(); 
    return rotatedImage; 
} 

但是圖像不繞其中心旋轉。我已經嘗試了各種與我的旋轉連接的變換，以使它圍繞中心旋轉，但無濟於事。我錯過了一招嗎？這是甚至可能的，因爲我旋轉的上下文而不是圖像？

越來越絕望的做出這項工作，所以任何幫助將不勝感激。

戴夫

編輯：我已經多次詢問我boundingRect代碼，所以在這裏它是：

- (CGRect) getBoundingRectAfterRotation: (CGRect) rectangle byAngle: (CGFloat) angleOfRotation { 
    // Calculate the width and height of the bounding rectangle using basic trig 
    CGFloat newWidth = rectangle.size.width * fabs(cosf(angleOfRotation)) + rectangle.size.height * fabs(sinf(angleOfRotation)); 
    CGFloat newHeight = rectangle.size.height * fabs(cosf(angleOfRotation)) + rectangle.size.width * fabs(sinf(angleOfRotation)); 

    // Calculate the position of the origin 
    CGFloat newX = rectangle.origin.x + ((rectangle.size.width - newWidth)/2); 
    CGFloat newY = rectangle.origin.y + ((rectangle.size.height - newHeight)/2); 

    // Return the rectangle 
    return CGRectMake(newX, newY, newWidth, newHeight); 
} 

Answer 1

行 - 最後我似乎已經做到了。任何關於正確性的評論都會很有用......需要一個平移，一個旋轉，一個縮放和一個從繪圖矩形位置的偏移來使它工作。代碼在這裏：

CGAffineTransform transform = CGAffineTransformIdentity; 
transform = CGAffineTransformTranslate(transform, boundingRect.size.width/2, boundingRect.size.height/2); 
transform = CGAffineTransformRotate(transform, angle); 
transform = CGAffineTransformScale(transform, 1.0, -1.0); 

CGContextConcatCTM(context, transform); 

// Draw the image into the context 
CGContextDrawImage(context, CGRectMake(-imageView.image.size.width/2, -imageView.image.size.height/2, imageView.image.size.width, imageView.image.size.height), imageView.image.CGImage); 

// Get an image from the context 
rotatedImage = [UIImage imageWithCGImage: CGBitmapContextCreateImage(context)];