C# .NET Core 图像转换器

Question

我正在尝试在我的 ASP.NET Core 项目中使用 ImageConverter 类将 Image 转换为 byte[]，但我似乎找不到该类。

我已经安装了System.Drawing.Common包，但是还是找不到。

我正在使用 .NET Core 3.1。

Answer 1

如果在 .NET Core 3.1 上，ImageConverter 需要 System.Windows.Extensions 包：

https://docs.microsoft.com/en-us/dotnet/api/system.drawing.imageconverter?view=netcore-3.1

在 .NET 5 中，它包含在 System.Drawing.Common：

https://docs.microsoft.com/en-us/dotnet/api/system.drawing.imageconverter?view=net-5.0

Answer 2

您可以轻松地将图像转换为字节。

protected virtual byte[] LoadPictureFromFile(string filePath)
{
   if (!File.Exists(filePath))
       return new byte[0];

   return File.ReadAllBytes(filePath);
}

额外帮助..

    public byte[] ResizeImage(byte[] pictureBinary,int newWidth, int newHeight)
    {
        byte[] pictureBinaryResized;
        using (var stream = new MemoryStream(pictureBinary))
        {
            Bitmap b = null;
            try
            {
                //try-catch to ensure that picture binary is really OK. Otherwise, we can get "Parameter is not valid" exception if binary is corrupted for some reasons
                b = new Bitmap(stream);
            }
            catch (ArgumentException exc)
            {
              // log error
            }

            if (b == null)
            {
                //bitmap could not be loaded for some reasons
                return new byte[0];
            }

            using (var destStream = new MemoryStream())
            {

                ImageBuilder.Current.Build(b, destStream, new ResizeSettings
                {
                    Width = newWidth,
                    Height = newHeight,
                    Scale = ScaleMode.Both,
                    Quality = _mediaSettings.DefaultImageQuality
                });
                pictureBinaryResized = destStream.ToArray();
                b.Dispose();
            }
        }

        return pictureBinaryResized;
    }

Answer 3

您可以尝试查看这个来加快速度，而不是 ImageConverter：

将位图保存到流中：

bitmap.save(stream);

或者打开图片文件：

FileStream stream = new FileStream(imageFilePath, FileMode.Open, FileAccess.Read);

然后简单地使用 Stream2Bytes：

byte[] OO7b = Stream2Bytes(stream);

这是 Stream2Bytes 方法：

public byte[] Stream2Bytes(Stream stream, int chunkSize = 1024)
{
    if (stream == null)
    {
        throw new System.ArgumentException("Parameter cannot be null", "stream");
    }

    if (chunkSize < 1)
    {
        throw new System.ArgumentException("Parameter must be greater than zero", "chunkSize");
    }

    if (chunkSize > 1024 * 64)
    {
        throw new System.ArgumentException(String.Format("Parameter must be less or equal {0}", 1024 * 64), "chunkSize");
    }

    List<byte> buffers = new List<byte>();

    using (BinaryReader br = new BinaryReader(stream))
    {
        byte[] chunk = br.ReadBytes(chunkSize);

        while (chunk.Length > 0)
        {
            buffers.AddRange(chunk);
            chunk = br.ReadBytes(chunkSize);
        }
     }

     return buffers.ToArray();
}