如何旋转图像文件？

Question

如何轻松地旋转保存在文档目录中的图像文件？

我的代码保存它：

(...) 
UIImage *capturedImage = UIGraphicsGetImageFromCurrentImageContext(); 
NSData* imageData = UIImageJPEGRepresentation(capturedImage, 1.0); 
NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 
[imageData writeToFile:[docDir stringByAppendingPathComponent:@"saved.jpg"] atomically:NO]; 
UIGraphicsEndImageContext(); 

Answer 1

轻松使用CGContextRotateCTM()实现：

发现在一个SO答案在这里：How to Rotate a UIImage 90 degrees?

static inline double radians (double degrees) {return degrees * M_PI/180;} 
- (UIImage*) rotateImage:(UIImage*)src rotationDirection:(UIImageOrientation)orientation { 
    UIGraphicsBeginImageContext(src.size); 

    CGContextRef context(UIGraphicsGetCurrentContext()); 
    if (orientation == UIImageOrientationRight) { 
     CGContextRotateCTM (context, radians(90)); 
    } else if (orientation == UIImageOrientationLeft) { 
     CGContextRotateCTM (context, radians(-90)); 
    } else if (orientation == UIImageOrientationDown) { 
     // NOTHING 
    } else if (orientation == UIImageOrientationUp) { 
     CGContextRotateCTM (context, radians(90)); 
    } 

    [src drawAtPoint:CGPointMake(0, 0)]; 

    return UIGraphicsGetImageFromCurrentImageContext(); 
}