Question

我有一个带有图像的UIImageView。我通过将UIImageView的transform属性设置为CGAffineTransformMakeRotation（angle），在显示之前旋转了图像，其中angle是以弧度表示的角度。

我希望能够创建另一个与我在视图中可以看到的旋转版本对应的UIImage。

我几乎在那里，通过旋转图像上下文，我得到一个旋转的图像：

- (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;
 }

然而，图像不会围绕其中心旋转。我已经尝试了与我的旋转连接的各种变换，以使其围绕中心旋转，但无济于事。我错过了一招吗？这是否可能，因为我正在旋转上下文而不是图像？

现在急需让这项工作，所以任何帮助都会受到赞赏。

戴夫

编辑：我多次被问过我的boundingRect代码，所以这里是：

- (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

好的 - 最后我似乎已经做到了。任何关于正确性的评论都是有用的......需要翻译，旋转，缩放和绘制矩形位置的偏移以使其工作。代码在这里：

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)];

从旋转的UIImageView创建UIImage

1 个答案: