iOS-处理相机拍照&相册选择图片的方向矫正

问题

如果把通过相机获取到的图片，直接进行操作，比如裁剪、缩放等原图片都会旋转。

产生原因

1、如果该图片大于2M，会自动旋转；否则不旋转。

UIImage *originalImg = [dict objectForKey:UIImagePickerControllerOriginalImage];

2、用相机拍摄出来的照片含有EXIF信息，UIImage的imageOrientation属性指的就是EXIF中的Orientaion信息。
如果我们忽略Orientaion信息，而直接对照片进行像素处理或者drawInRect等操作，得到的结果是翻转或者旋转90之后的样子。
这是因为我们执行像素处理或者drawInRect等操作之后，imageOrientaion信息被删除了，imageOrientaion被重设为0，造成照片内容和imageOrientaion不匹配。

解决办法

在UIImage Category中写一个处理图片方向的方法，然后在相机拍照获取到图片后调用，就可以解决原始图片旋转的问题了，下面是UIImage类别的方法源码，可直接复制调用哦~~~

+ (UIImage *)fixOrientation:(UIImage *)image {
    if (image.imageOrientation == UIImageOrientationUp)
        return image;
    CGAffineTransform transform = CGAffineTransformIdentity;
    
    switch (image.imageOrientation) {
        case UIImageOrientationDown:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width, image.size.height);
            transform = CGAffineTransformRotate(transform,M_PI);
            break;
            
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width,0);
            transform = CGAffineTransformRotate(transform,M_PI_2);
            break;
            
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform,0, image.size.height);
            transform = CGAffineTransformRotate(transform, -M_PI_2);
            break;
        default:
            break;
    }
    
    switch (image.imageOrientation) {
        case UIImageOrientationUpMirrored:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width,0);
            transform = CGAffineTransformScale(transform, -1,1);
            break;
            
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.height,0);
            transform = CGAffineTransformScale(transform, -1,1);
            break;
        default:
            break;
    }
    
    CGContextRef ctx = CGBitmapContextCreate(NULL, image.size.width, image.size.height,
                                             CGImageGetBitsPerComponent(image.CGImage),0,
                                             CGImageGetColorSpace(image.CGImage),
                                             CGImageGetBitmapInfo(image.CGImage));
    CGContextConcatCTM(ctx, transform);
    switch (image.imageOrientation) {
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            // Grr...
            CGContextDrawImage(ctx,CGRectMake(0,0,image.size.height,image.size.width), image.CGImage);
            break;
            
        default:
            CGContextDrawImage(ctx,CGRectMake(0,0,image.size.width,image.size.height), image.CGImage);
            break;
    }
    
    CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
    UIImage *img = [UIImage imageWithCGImage:cgimg];
    CGContextRelease(ctx);
    CGImageRelease(cgimg);
    return img;
}