[iOS] 图片旋转

/**
 旋转图片
 @param radians 旋转弧度
 */
- (UIImage *)lj_imageRotatedByRadians:(CGFloat)radians {
    return [self lj_imageRotatedByDegrees:RadiansToDegrees(radians)];
}

/**
 旋转图片

 @param degrees 旋转角度
 */
- (UIImage *)lj_imageRotatedByDegrees:(CGFloat)degrees {
    
    // calculate the size of the rotated view's containing box for our drawing space
    UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.size.width, self.size.height)];
    CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
    rotatedViewBox.transform = t;
    CGSize rotatedSize = rotatedViewBox.frame.size;
    rotatedViewBox = nil;
    
    // Create the bitmap context
    UIGraphicsBeginImageContextWithOptions(rotatedSize, NO, 0.0);
    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, DegreesToRadians(degrees));
    
    // Now, draw the rotated/scaled image into the context
    CGContextScaleCTM(bitmap, 1.0, -1.0);
    CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);
    
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
    
}