相机(摄像头)获取到的图片自动旋转90度解决办法

来源：互联网发布：软件初级工程师编辑：程序博客网时间：2024/06/06 00:51

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orientation信息。

如果我们忽略orientation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。

所以，在对照片进行处理之前，先将照片旋转到正确的方向，并且返回的imageOrientaion为0。

下面这个方法就是一个UIImage category中的方法，用它可以达到以上目的。

- (UIImage *)fixOrientation:(UIImage *)aImage{    // No-op if the orientation is already correct    if (aImage.imageOrientation == UIImageOrientationUp)    {        return aImage;    }        // We need to calculate the proper transformation to make the image upright.    // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.    CGAffineTransform transform = CGAffineTransformIdentity;        switch (aImage.imageOrientation)    {        case UIImageOrientationDown:        case UIImageOrientationDownMirrored:        {            transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);            transform = CGAffineTransformRotate(transform, M_PI);        }            break;                    case UIImageOrientationLeft:        case UIImageOrientationLeftMirrored:        {            transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);            transform = CGAffineTransformRotate(transform, M_PI_2);        }            break;                    case UIImageOrientationRight:        case UIImageOrientationRightMirrored:        {            transform = CGAffineTransformTranslate(transform, 0, aImage.size.height);            transform = CGAffineTransformRotate(transform, -M_PI_2);        }            break;        default:            break;    }        switch (aImage.imageOrientation)    {        case UIImageOrientationUpMirrored:        case UIImageOrientationDownMirrored:        {            transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);            transform = CGAffineTransformScale(transform, -1, 1);        }            break;                    case UIImageOrientationLeftMirrored:        case UIImageOrientationRightMirrored:        {            transform = CGAffineTransformTranslate(transform, aImage.size.height, 0);            transform = CGAffineTransformScale(transform, -1, 1);        }            break;        default:            break;    }        // Now we draw the underlying CGImage into a new context, applying the transform    // calculated above.    CGContextRef ctx = CGBitmapContextCreate(NULL,                                             aImage.size.width,                                             aImage.size.height,                                             CGImageGetBitsPerComponent(aImage.CGImage),                                             0,                                             CGImageGetColorSpace(aImage.CGImage),                                             CGImageGetBitmapInfo(aImage.CGImage));    CGContextConcatCTM(ctx, transform);    switch (aImage.imageOrientation)    {        case UIImageOrientationLeft:        case UIImageOrientationLeftMirrored:        case UIImageOrientationRight:        case UIImageOrientationRightMirrored:        {            // Grr...            CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage);        }            break;                    default:        {            CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage);        }            break;    }        // And now we just create a new UIImage from the drawing context    CGImageRef cgimg = CGBitmapContextCreateImage(ctx);    UIImage * img = [UIImage imageWithCGImage:cgimg];    CGContextRelease(ctx);    CGImageRelease(cgimg);    return img;}

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