How to use ClientDC::GetPixel to get the pixel's RGB value when I call TextOut?

[wangningyu]

Hello ! I debug along time.but isn't success! it isn't output "Call GetPixel Failed !", but isn't goto the other judgment. the code like this:

class CTestDlg : public CDialog
{
public:
// ......

public:
void TextOutPut(CString str,
HFONT hNew,
HFONT &hOld,
SIZE &szt)
{
CClientDC dc(this);

	// Set the back and text color 
	GetWindowRect(&rt);
	dc.SetBkColor(RGB(255,255,255));
	dc.SetTextColor(RGB(0,0,0));
	dc.SetMapMode(MM\_TEXT);

	// Use CClientDC::TextOut
	hOld = (HFONT)::SelectObject(dc,hNew);
	dc.TextOut(0,0,str);

	// I can use this function to get the szt's value like 32\*33
	GetTextExtentPoint32(dc,str,str.GetLength(),&szt);

	COLORREF cr;
	POINT	 pt;

	// Now start to find the pixcel's RGB value.
	for (int i=0; i<szt.cy; i++)
	{
		for (int j=0; j<szt.cx; j++)
		{
			pt.x = j;
			pt.y = i;
			cr = dc.GetPixel(pt);

			if( -1 == cr )
			{
				TRACE("Call GetPixel Failed !\\r\\n");
			}
			else if( RGB(255,255,255) == cr )
			{
				CString str;
				str.Format("cur pix position: x=%d y=%d is white.",j,i);
				TRACE(str);
				// Do something.
			}
			else if( RGB(0,0,0) == cr )
			{
				CString str;
				str.Format("cur pix position: x=%d y=%d is black.",j,i);
				TRACE(str);
				// Do something.
			}
		}
	}
}

};

I think this maybe the GetPixel 's parents is wrong. How to solve this problem ? Thanks for your reply ! Best regards !

[CPallini]

What is the cr value? :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

[wangningyu]

COLORREF cr

maybe the cr is other color's RGB value. but I call this functions,so it doesn't be other value,isn't it ?

dc.SetBkColor(RGB(255,255,255));
dc.SetTextColor(RGB(0,0,0));

[CPallini]

Why don't you use the debugger to see what's cr value, at runtime? :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]