Transparent background on winforms?

Question

I wanted to make my windows form transparent so removed the borders, controls and everything leaving only the forms box, then I tried to the BackColor and TransparencyKey to transparent but it didnt work out as BackColor would not accept transparent color. After searching around I found this at msdn:

SetStyle(ControlStyles.UserPaint, true);
SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
SetStyle(ControlStyles.SupportsTransparentBackColor, true);
this.BackColor = Color.Transparent;
this.TransparencyKey = BackColor;

Unhappyly it did not work either. I still get the grey or any other selected color background.

All I wanted to do is to have the windows form transparent so I could use a background image that would act as if it was my windows form.

I searched around here and saw many topics in regards opacity which is not what I am looking for and also saw some in regards this method I was trying but have not found an answer yet.

Hope anyone can light my path.

UPDATE:

image removed as problem is solved

Answer 1

The manner I have used before is to use a wild color (a color no one in their right mind would use) for the BackColor and then set the transparency key to that.

this.BackColor = Color.LimeGreen;
this.TransparencyKey = Color.LimeGreen;

Answer 2

My solution was extremely close to Joel's (Not Etherton, just plain Joel):

public partial class WaitingDialog : Form
{
    public WaitingDialog()
    {
        InitializeComponent();

        SetStyle(ControlStyles.SupportsTransparentBackColor, true);
        this.BackColor = Color.Transparent;
        this.TransparencyKey = Color.Transparent; // I had to add this to get it to work.

        // Other stuff
    }

    protected override void OnPaintBackground(PaintEventArgs e) { /* Ignore */ }
}

Answer 3

I had drawn a splash screen (32bpp BGRA) with "transparent" background color in VS2013 and put a pictureBox in a form for display. For me a combination of above answers worked:

    public Form1()
    {
        InitializeComponent();

        SetStyle(ControlStyles.SupportsTransparentBackColor, true);
        this.BackColor = this.pictureBox1.BackColor;
        this.TransparencyKey = this.pictureBox1.BackColor;
    }

So make sure you use the same BackColor everywhere and set that color as the TransparencyKey.

Answer 4

A simple solution to get a transparent background in a windows form is to overwrite the OnPaintBackground method like this:

protected override void OnPaintBackground(PaintEventArgs e)
{
    //empty implementation
}

(Notice that the base.OnpaintBackground(e) is removed from the function)

Answer 5

I tried almost all of this. but still couldn't work. Finally I found it was because of 24bitmap problems. If you tried some bitmap which less than 24bit. Most of those above methods should work.

Answer 6

What works for me is using a specific color instead of the real ability of .png to represent transparency.

So, what you can do is take your background image, and paint the transparent area with a specific color (Magenta always seemed appropriate to me...).

Set the image as the Form's BackgrounImage property, and set the color as the Form's TransparencyKey. No need for changes in the Control's style, and no need for BackColor.

I've tryed it right now and it worked for me...