在Mac OS X上使用System.Drawing.Common将BMP转换为TIFF

问题描述

我正尝试在Mac OS上使用System.Drawing.Common和以下C＃代码（.NET CORE 3.1）将BMP图像转换为tiff图像：

        public void SaveBitmapAsTiff(string location,Bitmap image)
        {

            var imageCodecInfo = GetEncoderInfo("image/tiff");
            var encoder = Encoder.Compression;
            var encoderParameters = new EncoderParameters(1);
            
            var encoderParameter = new EncoderParameter(
                encoder,(long)EncoderValue.CompressionLZW);
            encoderParameters.Param[0] = encoderParameter;
            location = location.Replace(".bmp","");
            image.Save(location + ".tiff",imageCodecInfo,encoderParameters);
            // image.Save(location + ".tiff",ImageFormat.Tiff); Also tried this method overload
        }
        
        private static ImageCodecInfo GetEncoderInfo(string mimeType)
        {
            int j;
            ImageCodecInfo[] encoders;
            encoders = ImageCodecInfo.GetimageEncoders();
            for(j = 0; j < encoders.Length; ++j)
            {
                if(encoders[j].MimeType == mimeType)
                    return encoders[j];
            }
            return null;
        }

location参数包含我们要写入的文件路径，image参数包含我们从磁盘加载的位图。

当我尝试运行此代码时，出现以下异常：

Unhandled exception. System.NotImplementedException: Not implemented.
   at System.Drawing.SafeNativeMethods.Gdip.CheckStatus(Int32 status)
   at System.Drawing.Image.Save(String filename,ImageCodecInfo encoder,EncoderParameters encoderParams)
   at System.Drawing.Image.Save(String filename,ImageFormat format)
   at BmpTiffConverter.Services.FileService.SaveBitmapAsTiff(String location,Bitmap image) in /Users/tomcoldenhoff/Documents/ReSoftware/Repositories/BmpTiffConverter/BmpTiffConverter/Services/FileService.cs:line 54
   at BmpTiffConverter.Services.ConverterService.ConvertBmpToTiff(String inputPath,String outputPath) in /Users/tomcoldenhoff/Documents/ReSoftware/Repositories/BmpTiffConverter/BmpTiffConverter/Services/ConverterService.cs:line 20

我的Google搜索表明我必须安装已经使用brew install mono-libgdiplus和brew upgrade mono-libgdiplus的libgdiplus。

我还通过安装runtime.osx.10.10-x64.CoreCompat.System.Drawing软件包尝试了@Andy的建议答案，很遗憾，这没有用。

还有其他建议吗？

解决方法

问题是mono-libgdiplus没有实现EncoderValue.CompressionLZW编码器参数。我建议不要使用该库，而是安装此nuget包：

runtime.osx.10.10-x64.CoreCompat.System.Drawing

一旦我添加了该软件包，您的代码就会完美运行。

,

不幸的是，我没有Mac可以测试。我在Windows和Ubuntu 20上使用DotNet Core 3.1测试了您的代码，您的代码似乎可以正常工作。我只能猜测，这可能与您如何创建或修改Bitmap有关。

下面是我在Linux下创建项目的方式。 dotnet add package是我添加System.Drawing.Common NuGet程序包的方式。我不确定它在Mono上如何工作，或者您是否在使用Mono。

> dotnet new console
> dotnet add package System.Drawing.Common
> dotnet restore

我编辑了program.cs

> dotnet build
> dotnet run

，它运行得很好。我现在可以在任何图像查看器中打开tiff图像。

从代码样式的角度来看，我建议进行很多更改。我知道您遵循了MSDN的代码示例，但就目前而言，它们的示例并不十分清楚。我刚刚复制并粘贴了整个.cs文件，并在各种修改中添加了注释。编写清晰的代码与编写工作代码同等重要。

using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;

class Program
{
    // made the function more generic Bitmap inherits from Image and Image contains
    // the save feature so it might as well be made more general
    public static void SaveImageAsTiff(string location,Image image)
    {
        // fetch tiffCodec (using System.Linq) 
        // Much clearer than that other funny loop code on MSDN
        var tiffCodec = ImageCodecInfo.GetImageEncoders().
             Where(info => info.MimeType == "image/tiff").First();
        //.First() throws an exception if the list is empty
        //.FirstOrDefault() returns null if the list is empty

        // create encoderParameters
        // this structure is much clearer IMO
        // (Can you see that there is now a color depth parameter?)
        var encoderParameters = new EncoderParameters(2) 
        {
            Param = new EncoderParameter[]{
                new EncoderParameter(Encoder.Compression,(long)EncoderValue.CompressionLZW),new EncoderParameter(Encoder.ColorDepth,24L)
            }
        };

        // save image using codec and encoder parameters
        // it is common behavior to just save the file with the given location parameter 
        // and not to try do some extension conversion
        image.Save(location,tiffCodec,encoderParameters);
    }

    static void Main(string[] args)
    {
        // original bitmap location
        // (Yes forward slashes work on Windows so relative file paths are simple to handle)
        string bmpLocation = @"C:/Images/test.bmp";
        //string bmpLocation = @"~/Images/test.bmp"; // test on Linux

        // tidy way to convert file extensions of a path in C#
        string tiffLocation = System.IO.Path.ChangeExtension(bmpLocation,"tiff");

        // open image and force it to be a bitmap for examples sakes
        Bitmap bmpImage = new Bitmap(Image.FromFile(bmpLocation));

        // save image as tiff
        SaveImageAsTiff(tiffLocation,bmpImage);
    }
}