C#实现图片转Base64字符串，以及base64字符串在Markdown文件内复原的演示

static void Main(string[] args)
{
var file = @"xxx.jpg";
var data = Wesky.Net.OpenTools.Converter.ImageConvert.ConvertImageToBase64(file);
var mdString = $"![avatar]({data})";
    Console.WriteLine(mdString);
}

/// <summary>
/// 将图片文件转换为 Base64 编码的字符串。
/// Converts an image file to a Base64-encoded string.
/// </summary>
/// <param name="imagePath">图片文件的路径。Path to the image file.</param>
/// <returns>返回 Base64 编码的图片字符串。Returns a Base64-encoded image string.</returns>
public static string ConvertImageToBase64(string imagePath)
{
if (!File.Exists(imagePath))
    {
throw new FileNotFoundException("指定的图片路径不存在。Specified image path does not exist.");
    }
byte[] imageBytes = File.ReadAllBytes(imagePath);
string mimeType = GetMimeType(imagePath);
string base64String = Convert.ToBase64String(imageBytes);
return $"data:{mimeType};base64,{base64String}";
}

case ".bmp":
return "image/bmp";
case ".gif":
return "image/gif";
case ".jpg":
case ".jpeg":
return "image/jpeg";
case ".png":
return "image/png";
case ".tif":
case ".tiff":
return "image/tiff";
case ".ico":
    return "image/x-icon";