解决图库选择上传图片时旋转 90° 问题

在项目开发中，有时候图库选择或拍照上传图片时，会出现图片旋转 90° 的问题，暂发现大于 2M 的图会出现这个问题，下面是解决方法，在上传图片之前进行图片的方向调整即可。

//修正图片旋转问题
- (UIImage *)fixImageOrientation:(UIImage *)image {

    //image 的 imageOrientation 属性记录有图片的方向信息
    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 contextRef = CGBitmapContextCreate(NULL, image.size.width, image.size.height, CGImageGetBitsPerComponent(image.CGImage), 0, CGImageGetColorSpace(image.CGImage), CGImageGetBitmapInfo(image.CGImage));
    
    CGContextConcatCTM(contextRef, transform);
    switch (image.imageOrientation) {
            
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            
            CGContextDrawImage(contextRef, CGRectMake(0,0,image.size.height,image.size.width), image.CGImage);
            break;
            
        default:
            CGContextDrawImage(contextRef, CGRectMake(0,0,image.size.width,image.size.height), image.CGImage);
            break;
    }
    
    CGImageRef imgRef = CGBitmapContextCreateImage(contextRef);
    UIImage *newImage = [UIImage imageWithCGImage: imgRef];
    CGContextRelease(contextRef);
    CGImageRelease(imgRef);
    return newImage;
}