Saving DrawingVisual to an image file with a given DPI

Question

I have got a WPF application, and I would like to save a Canvas to a file with a correct DPI value. The Canvas size is the real physical size, eg. 20x10 cm, at 300 DPI, so it\'s

Answer 1

It seems the solution is the Bitmap SetResolution, after all. I tested it, and it looks like not affect the image quality after the JpegBitmapEncoder()! And the image resolution is untouched, keep the metadata, only the DPI will change!

Helped this documentation: https://docs.microsoft.com/en-us/dotnet/framework/winforms/advanced/how-to-set-jpeg-compression-level

JpegBitmapEncoder encoder = new JpegBitmapEncoder();
encoder.QualityLevel = 100;
BitmapFrame bFrame = BitmapFrame.Create(rtb, null, meta, icc);
encoder.Frames.Add(bFrame);

using (var stream = new MemoryStream())
{
    encoder.Save(stream);

    using (var bmpOutput = new System.Drawing.Bitmap(stream))
    {
        System.Drawing.Imaging.ImageCodecInfo myEncoder = GetEncoder(ImageFormat.Jpeg); 

        var encoderParameters = new System.Drawing.Imaging.EncoderParameters(1);
        encoderParameters.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);

        bmpOutput.SetResolution(300.0f, 300.0f);
        bmpOutput.Save(filePath, myEncoder, encoderParameters);
    }
}