Cannot save a Transparent PNG from my canvas in C#

Question

I made a WPF canvas program which lets users add some PNG templates and make their own new design.

I could complete the working

However when I try to save , I get the white background Is there any way to get a transparent output ?

This is my code on saving image

public void SaveTo(string f)
    {
        Visual v = Dc;
        /// get bound of the visual
        Rect b = VisualTreeHelper.GetDescendantBounds(v);

        /// new a RenderTargetBitmap with actual size of c
        RenderTargetBitmap r = new RenderTargetBitmap(
            (int)b.Width, (int)b.Height,
            96, 96, PixelFormats.Pbgra32);

        /// render visual
        r.Render(v);

        /// new a JpegBitmapEncoder and add r into it 
        JpegBitmapEncoder e = new JpegBitmapEncoder();
        e.Frames.Add(BitmapFrame.Create(r));

        /// new a FileStream to write the image file
        FileStream s = new FileStream(f,
            FileMode.OpenOrCreate, FileAccess.Write);
        e.Save(s);
        s.Close();
    }

you know it's perfectly legal to use more than one letter for a variable name :) — thumbmunkeys, Sep 13 '14 at 18:55
Have a look on this - http://stackoverflow.com/questions/388677/can-you-make-an-alpha-transparent-png-with-c — sobby01, Sep 13 '14 at 18:57

score 2 · Answer 1 · answered Sep 13 '14 at 18:57

2

You are encoding to a Jpeg.

Jpegs have no transparency information (aka alpha channel).

You should use a PngBitmapEncoder.

answered Sep 13 '14 at 18:57

thumbmunkeys

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Cannot save a Transparent PNG from my canvas in C#

1 Answers1