UIImage iPhone 旋转 37.8 度

Question

从设备加载图像后，我需要将其旋转 37.8 度，然后将其显示在视图上。

Objective-C中有没有可以实现图像旋转的函数？

伊恩

Answer 1

旋转视图：

imageView.transform = CGAffineTransformMakeRotation(37.8°);

旋转图像，

1. 计算旋转后图像所占用的宽度和高度。
2. 通过UIGraphicsBeginImageContext创建一个CGContext。
3. CGContextRotateCTM(UIGraphicsGetCurrentContext(), 37.8°);
4. [yourImage drawAtPoint:...];
5. UIGraphicsGetImageFromCurrentImageContext(); 并使用此图像。
6. 释放上下文。

Answer 2

是的，请参阅我对此问题的回答：有关旋转滑块的问题

要将度数转换为弧度（对于positionInRadians arg），请使用以下函数：

CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;};

Answer 3

要旋转图像，请尝试以下操作：

-(IBAction)rotateImageClick:(id)sender{

    UIImage *image2=[[UIImage alloc]init];
    image2 = [self imageRotatedByDegrees:self.roateImageView.image deg:(90)]; //Angle by 90 degree
    self.roateImageView.image = image2;
    imgData= UIImageJPEGRepresentation(image2,0.9f);

}

此方法允许您将图像旋转任意数量：

- (UIImage *)imageRotatedByDegrees:(UIImage*)oldImage deg:(CGFloat)degrees{

    // calculate the size of the rotated view's containing box for our drawing space
    UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,oldImage.size.width, oldImage.size.height)];

    CGAffineTransform t = CGAffineTransformMakeRotation(degrees * M_PI / 180);
    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 so we will rotate and scale around the center.
    CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);

    //   // Rotate the image context
    CGContextRotateCTM(bitmap, (degrees * M_PI / 180));

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

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

}

请参阅 此链接了解更多信息。