在aspnetcore Web API中使用图像的EXIF数据旋转/翻转图像

Question

我有一个Web应用程序，用户可以在该Web应用程序上通过直接用手机拍摄照片来上传个人资料照片。由于图像的EXIF方向，前端必须在显示图片之前变换图像（旋转/翻转）。但是，我希望在保存图片之前在后端执行转换，以避免在前端进行转换。后端是用C＃编写的.net core 2.0应用程序。

是否有人对可用于访问EXIF数据并进行转换的库提出建议。

到目前为止，我已经找到https://github.com/SixLabors/ImageSharp并浏览了有关如何使用它的文档。

Answer 1

ImageSharp库中已经有一种方法。AutoOrient()为您处理一切。

https://sixlabors.github.io/docs/api/ImageSharp/SixLabors.ImageSharp.Processing.Transforms.AutoOrientExtensions.html

private byte[] TransformAvatarIfNeeded(byte[] imageInBytes)
{
    using (var image = Image.Load(imageInBytes, out var imageFormat ))
    {
        image.Mutate(x => x.AutoOrient());
        return ImageToByteArray(image, imageFormat);
    }
}

Answer 2

最后，我将其与ImageSharp库一起使用。这可能对其他人有帮助。

    private byte[] TransformAvatarIfNeeded(byte[] imageInBytes)
    {
        using (var image = Image.Load(imageInBytes))
        {
            ExifValue exifOrientation = image.MetaData?.ExifProfile?.GetValue(ExifTag.Orientation);

            if (exifOrientation == null) return imageInBytes;

            RotateMode rotateMode;
            FlipMode flipMode;
            SetRotateFlipMode(exifOrientation, out rotateMode, out flipMode);

            image.Mutate(x => x.RotateFlip(rotateMode, flipMode));
            image.MetaData.ExifProfile.SetValue(ExifTag.Orientation, (ushort)1);

            var imageFormat = Image.DetectFormat(imageInBytes);

            return ImageToByteArray(image, imageFormat);
        }
    }

    private byte[] ImageToByteArray(Image<Rgba32> image, IImageFormat imageFormat)
    {
        using (var ms = new MemoryStream())
        {
            image.Save(ms, imageFormat);
            return ms.ToArray();
        }
    }

    private void SetRotateFlipMode(ExifValue exifOrientation, out RotateMode rotateMode, out FlipMode flipMode)
    {
        var orientation = exifOrientation.Value.ToString();

        switch (orientation)
        {
            case "2":
                rotateMode = RotateMode.None;
                flipMode = FlipMode.Horizontal;
                break;
            case "3":
                rotateMode = RotateMode.Rotate180;
                flipMode = FlipMode.None;
                break;
            case "4":
                rotateMode = RotateMode.Rotate180;
                flipMode = FlipMode.Horizontal;
                break;
            case "5":
                rotateMode = RotateMode.Rotate90;
                flipMode = FlipMode.Horizontal;
                break;
            case "6":
                rotateMode = RotateMode.Rotate90;
                flipMode = FlipMode.None;
                break;
            case "7":
                rotateMode = RotateMode.Rotate90;
                flipMode = FlipMode.Vertical;
                break;
            case "8":
                rotateMode = RotateMode.Rotate270;
                flipMode = FlipMode.None;
                break;
            default:
                rotateMode = RotateMode.None;
                flipMode = FlipMode.None;
                break;
        }