How can I convert image on the hard disk png to be transparent?

Question

private void ConvertImagestoTransparent(string filename)
{
    var image = new Bitmap(filename, PixelFormat.Format32bppArgb);
    using (var g = Graphics.FromImage(image))
    {
        g.DrawLine(Pens.Red, 0, 0, 135, 135);
    }
}

This give me error the new Bitmap is not getting filename:

Error 2 Argument 2: cannot convert from 'System.Drawing.Imaging.PixelFormat' to 'bool'

Also not getting Bitmap.

In the constructor:

DirectoryInfo d = new DirectoryInfo(@"C:\temp\images\");
Files = d.GetFiles("*.png");

Is it possible to convert the png images to transparent ? Will it lost quality ?

Answer 1

The Bitmap constructor you're using is only for loading existing images. If you want to create one, then you need to use this one like this:

var image = new Bitmap(theWidth, theHeight, PixelFormat.Format32bppArgb);

Then, you can save your image to a file like this:

image.Save(filename);

For your 2nd question, what do you mean by "convert the png images to transparent"? Do you want to remove the background color from the images?