e.Graphics.DrawImage is fading stretched image

[GregSenne]

This is in a class, the class inherits Panel.

Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        e.Graphics.DrawImage(_BackgroundImage, 0, 0, 300, 50)
        MyBase.OnPaint(e)
    End Sub

_BackgroundImage is set to a PNG image, 1 px wide x 50 px tall.

The goal is to have this image stretched to 300x50

Whenever I do it, it works, but it fades the image from left to right, so that at Left = 0, the image is solid, but at Left = 300, the image is transparent.



Thanks.

[ForumAccount]

Add this line before you run yours:

e.Graphics.CompositingMode = Drawing2D.CompositingMode.SourceCopy

[GregSenne]

Add this line before you run yours:

e.Graphics.CompositingMode = Drawing2D.CompositingMode.SourceCopy

So now it still fades, but fades to black instead of transparent.

Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        e.Graphics.CompositingMode = Drawing2D.CompositingMode.SourceCopy
        e.Graphics.DrawImage(_BackgroundImage, 0, 0, 300, 50)
        MyBase.OnPaint(e)
    End Sub

[MattP]

It's an interpolation problem when magnifying.

    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        With e.Graphics
            .InterpolationMode = Drawing2D.InterpolationMode.NearestNeighbor
            .PixelOffsetMode = Drawing2D.PixelOffsetMode.None
            .DrawImage(_BackgroundImage, 0, 0, 300, 50)
        End With
        MyBase.OnPaint(e)
    End Sub

[ForumAccount]

Why not just set the BackgroundImage of the Panel instead?

[GregSenne]

Why not just set the BackgroundImage of the Panel instead?

Actually, this code is just really dumbed down. I need the image to appear in the panel a certain distance off the left and right edge, and stretched to fit the rest of the panel.

[GregSenne]

It's an interpolation problem when magnifying.

    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        With e.Graphics
            .InterpolationMode = Drawing2D.InterpolationMode.NearestNeighbor
            .PixelOffsetMode = Drawing2D.PixelOffsetMode.None
            .DrawImage(_BackgroundImage, 0, 0, 300, 50)
        End With
        MyBase.OnPaint(e)
    End Sub

Thanks, it stopped the fading and is working properly.
Just one problem left. I adjusted it so that the image would start 20 px from the left border, and be 800 px wide.

e.Graphics.DrawImage(_BackgroundImage, 20, 0, 800, 16)

But when I look at it in the designer, the panel I draw is 614 px wide, but looks like this:


Even weirder, if I tell it to start 20 px in from the left border, and stretch to the width of the panel minus 40 (so there would be a 20px gap on each side, i get this):

The above image has this code:

Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
 
        e.Graphics.InterpolationMode = Drawing2D.InterpolationMode.NearestNeighbor
        e.Graphics.PixelOffsetMode = Drawing2D.PixelOffsetMode.None
        e.Graphics.DrawImage(_BackgroundImage, 20, 0, Me.Width - 40, Me.Height)
        Call MyBase.OnPaint(e)

If I set the width to 50 (same code as above just substitute me.Width - 40 for 50), it paints the background image 25 pixels wide.

I have tried adjusting the InterpolationMode, but everything besides NearestNeighbor shows up as a fade to transparent.
Thanks for the help.
Greg

Thanks.

[GregSenne]

Okay I just multiplied the width by 2 and it seems to work fine now. I have no idea why (Why would I have to double the width to get the desired width), but it is working

e.Graphics.DrawImage(_BackgroundImage, 20, 0, (Me.Width - 40) * 2, Me.Height)

[boops boops]

Try it with PixelOffsetMode=Half. Then the stretched pixel will be centred in the drawing rectangle. In default PixelOffsetMode, the pixel is centred on the origin. BB

[GregSenne]

Try it with PixelOffsetMode=Half. Then the stretched pixel will be centred in the drawing rectangle. In default PixelOffsetMode, the pixel is centred on the origin. BB

Thanks, I think I got it working just the way I want it now!