dotnet core 2.1+ System.Drawing.Common's grapic DrawImage 在 linux 中丢失透明度

Question

I'm trying add watermark to a jpeg picture using dotnetcore's system.drawing.common@4.5, everything is ok at my pc development environment, but when it run at linux server, the image's quality loss.

string inputFile = "inputFile.jpg";
string waterMarkFile = "waterMark.png";
var wmImage = Image.FromFile(waterMarkFile);
FileInfo input = new FileInfo(inputFile);
using (var stream = new MemoryStream())
{
    using (var fs = input.OpenRead())
    {
        fs.CopyTo(stream);
        using (var outputStream = new MemoryStream())
        {
            using (var img = Image.FromStream(stream))
            {
                using (var graphic = Graphics.FromImage(img))
                {
                    int initX = img.Width / 2;
                    int initY = img.Height / 2;
                    int wmWidth = img.Width * 0.1 > wmImage.Width ? (int)(img.Width * 0.1) : img.Width;
                    int wmHeight = (wmImage.Height * wmWidth) / wmImage.Width;
                    int offsetX = wmWidth / 2;
                    int offsetY = wmHeight / 2;
                    for (int x = initX; x < img.Width + wmWidth; x += (int)(wmWidth *  2.5))
                    {
                        for (int y = initY; y < img.Height + wmHeight; y += (int)(wmHeight * 2.5))
                        {
                            graphic.DrawImage(wmImage, x - offsetX, y - offsetY, wmWidth, wmHeight);
                            if (x != initX || y !=initY)
                            {
                                graphic.DrawImage(wmImage, initX - (x - initX) - offsetX , y - offsetY, wmWidth, wmHeight);
                                graphic.DrawImage(wmImage, initX - (x - initX) - offsetX, initY - (y - initY) - offsetY, wmWidth, wmHeight);
                                graphic.DrawImage(wmImage, x - offsetX, initY - (y - initY) - offsetY, wmWidth, wmHeight);
                            }
                        }
                    }
                    img.Save($"wm_{inputFile}");
                }
            }
        }
    }
}
wmImage.Dispose();

Answer 1

The problem still exists. I had the same problem with Debian based aspnet core images (3.1-buster-slim, 5.0-buster-slim). It looks like an old version of libgdiplus will be installed here. To run the app on the local environment is no solution for me (everythings has to run on kubernetes pods...)

I found two solutions:

1. Use Ubuntu based images (3.1-focal, 5.0-focal)
2. Use Debian (buster-slim) image, clone current libgdiplus form github an compile inside the image.

I created Dockerfiles for both scenarios and published a GitHub repository :