Display filter C#

Question

It's a little hard to explain what I need but i'll try: I need to write application (winform) which will be some kind of filter to image/other forms behind it. With one exception - all behind form should looks as is except of red (for example) color, which have to be replaced to any other specified color, white for example. So let's imagine I have opened windows Word with few lines of text. With red and black letters. So when i place my application above this text - it should "filter" red symbols and fill them to white. So as i understand this task: i have to snap area behind the form, then process it (replace colors) and after draw this image on my form body. Any links or keywords for solution? UPD: so - this is my final solution: - do form transparent (using TransparencyKey and BackColor properties) - place picturebox over the form - when we need to update image in picturebox - we replace current image with pictureBox1.Image = null;, then refreshing form with (this.Refresh()) and do…

Accepted Answer

you can create a snapshot of the desktop using the following code:

```
public Bitmap CaptureScreen()
{
    Bitmap b = new Bitmap(SystemInformation.VirtualScreen.Width, SystemInformation.VirtualScreen.Height);
    Graphics g = Graphics.FromImage(b);
    g.CopyFromScreen(0, 0, 0, 0, b.Size);
    g.Dispose();
    return b;
}
```

Replace the dimensions and position with the coordinates of your form. This way you get a bitmap of what's behind your form. Then you can do the color replacement on that bitmap.

Please note that due to settings like ClearType and other anti-aliasing mechanisms, you have to also take into account "intermediate pixels" when doing the color replacement. Otherwise things will look funny :-)

Display filter C#

Solution

Problem