[RESOLVED] How to implement a screen color picker

[Eri523]

Ok, first I have to apologize to anyone who might already have done some research in order to answer this question for bothering him yet again with a question that I can find the answer for myself in less than 24 hours. Of course I intended to do a tag search on Codeguru, a full-text search on CodeGuru and a Google search before posting. I did the tag search which didn't come up with any useful information, then got tired and went to bed. At the end of the next day I wrote my post above without doing any further search... My fault.

The following is a modified translation of the C# code I found in post #3 of http://www.codeguru.com/forum/showthread.php?t=476181:

System::Void Form1::btnScreenPicker_MouseMove(System::Object^  sender, System::Windows::Forms::MouseEventArgs^  e)
{
  if (static_cast<bool>(e->Button & System::Windows::Forms::MouseButtons::Left)) {
    Control ^ctl = static_cast<Control ^>(sender);
    Bitmap ^bmp = gcnew Bitmap(1, 1);
    Graphics ^gr = Graphics::FromImage(bmp);
    Point ptScreen = ctl->PointToScreen(e->Location);
    gr->CopyFromScreen(ptScreen.X, ptScreen.Y, 0, 0, Drawing::Size(1, 1));
    lblScreenPickerPreview->BackColor = bmp->GetPixel(0, 0);
  }
}

Yet again, that was one of these "easier than I expected" kind of things. And it doesn't contain a single Win32 API call, unlike some C# code I found in a post on that topic on codeproject.com which had lots of them.

In fact I already came across Graphics::CopyFromScreen() fefore while researching this topic, but for some obscure reason that I don't even know anymore now I didn't consider it to be a candidate.

Just before the version you see above, I had one that actually copied the entire screen before pickig a single pixel, and it imposed a CPU load of almost 100% as I was afraid of. But this 1-pixel version now only needs less than 10%. And as a side effect I now know how to capture anything from a single pixel up to the entire screen.

I was, BTW, surprised by the fact that I didn't even had to capture the mouse in order to reach any point on the screen. Is this the standard behaviour of a button or a special feature of the Windows Forms incarnation?