c# - 如何像字节数组一样处理使用 protobuf 存储的 System.Drawing.Image？

Question

我使用 protobuf-net v2.4.0 来存储 System.Drawing.Image 以及以下代理:

internal class SystemDrawingImageSurrogate
{
    public SystemDrawingImageSurrogate(byte[] data)
    {
        Data = data;            
    }

    public byte[] Data;

    public static implicit operator System.Drawing.Image(SystemDrawingImageSurrogate surrogate)
    {
        if (surrogate == null || surrogate.Data == null)
            return null;

        MemoryStream stream = new MemoryStream(surrogate.Data);
        var bitmap = new System.Drawing.Bitmap(stream);
        return bitmap;
    }

    public static implicit operator SystemDrawingImageSurrogate(System.Drawing.Image source)
    {
        if (source == null)
            return null;

        byte[] byteImage = (byte[])new ImageConverter().ConvertTo(source, typeof(byte[]));            
        return new SystemDrawingImageSurrogate(byteImage);            
    }
}

我用它来存储如下所示的类:

public class PersonWithPhotoSurrogate : PersonSurrogate
{        
    public PersonWithPhotoSurrogate(PersonWithPhoto pwp) : base(pwp)
    {

    }

    public int PictureWidth;

    public int PictureHeight;

    
    public System.Drawing.Image Photo;
}

public class FileBodySurrogate
{
    public FileBodySurrogate(FileBody fileBody) { }

    public List<Person> People;
}

现在我需要从 net-framework 迁移到 net6，因此我需要将 PersonWithPhotoSurrogate.Photo 字段声明为 byte[] 而不是 Image如下图:

public class PersonWithPhotoSurrogate : PersonSurrogate
{        
    public PersonWithPhotoSurrogate(PersonWithPhoto pwp) : base(pwp)
    {

    }

    public int PictureWidth;

    public int PictureHeight;

    
    public /*System.Drawing.Image*/ byte[] Photo;
}

在读取存储的旧文件时，如何处理此问题以保持向后兼容性？

Answer 1

您的 SystemDrawingImageSurrogate 在模型中添加了一个额外的层，因此，如果您从 Image 切换到简单的 byte[]，您'仍然需要表示该层；也许(未经测试):

public class PersonWithPhotoSurrogate : PersonSurrogate
{        
    public PersonWithPhotoSurrogate(PersonWithPhoto pwp) : base(pwp)
    {

    }

    public int PictureWidth;

    public int PictureHeight;

    
    public ImageWrapper Photo;
}

public class ImageWrapper
{
    public byte[] Data;
}

显然具有与原始模型相同的标签编号。您不应该需要替代件 - 您只需要模型看起来与替代件的相同。