iOS将image转90,180,270度的方法

http://blog.sina.com.cn/s/blog_6602ffbc0101ckx3.html

这里要分享的是将image旋转，而不是将imageView旋转，原理就是使用quartz2D来画图片，然后使用ctm变幻来实现旋转。

注：quartz2D的绘图左边和oc里面的绘图左边不一样，导致绘画出的图片是反转的。所以一上来得使它转正再进行进一步的旋转等

 

+ (UIImage *)image:(UIImage *)image rotation:(UIImageOrientation)orientation

{

    long double rotate = 0.0;

    CGRect rect;

    float translateX = 0;

    float translateY = 0;

    float scaleX = 1.0;

    float scaleY = 1.0;

    

    switch (orientation) {

        case UIImageOrientationLeft:

            rotate = M_PI_2;

            rect = CGRectMake(0, 0, image.size.height, image.size.width);

            translateX = 0;

            translateY = -rect.size.width;

            scaleY = rect.size.width/rect.size.height;

            scaleX = rect.size.height/rect.size.width;

            break;

        case UIImageOrientationRight:

            rotate = 3 * M_PI_2;

            rect = CGRectMake(0, 0, image.size.height, image.size.width);

            translateX = -rect.size.height;

            translateY = 0;

            scaleY = rect.size.width/rect.size.height;

            scaleX = rect.size.height/rect.size.width;

            break;

        case UIImageOrientationDown:

            rotate = M_PI;

            rect = CGRectMake(0, 0, image.size.width, image.size.height);

            translateX = -rect.size.width;

            translateY = -rect.size.height;

            break;

        default:

            rotate = 0.0;

            rect = CGRectMake(0, 0, image.size.width, image.size.height);

            translateX = 0;

            translateY = 0;

            break;

    }

    

    UIGraphicsBeginImageContext(rect.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    //做CTM变换

    CGContextTranslateCTM(context, 0.0, rect.size.height);

    CGContextScaleCTM(context, 1.0, -1.0);

    CGContextRotateCTM(context, rotate);

    CGContextTranslateCTM(context, translateX, translateY);

    

    CGContextScaleCTM(context, scaleX, scaleY);

    //绘制图片

    CGContextDrawImage(context, CGRectMake(0, 0, rect.size.width, rect.size.height), image.CGImage);

    

    UIImage *newPic = UIGraphicsGetImageFromCurrentImageContext();

    

    return newPic;

}