How to get the pixel color from a virtual device context ?

[wangningyu]

I want to get some gdi elements color infomation. when I used TextOut function to draw the strings in the device context.but I doesn't want to output the strings in a really device context in the program's window. so I found this way :

#include

#pragma comment(lib,"user32.lib")

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR pszCmdLine, int cmdShow)
{
// create a virtual dc to draw elements.
HDC hdcScreen = CreateDC("DISPLAY", NULL, NULL, NULL);
HDC hdcCompatible = CreateCompatibleDC(hdcScreen);
CString m_strText = _T("Hello");
SIZE m_sz;

if(hdcCompatible == NULL)
{
    MessageBox(NULL,\_T("CreateCompatibleDC Failed !"),NULL,NULL);
    return -1;
}

// then set the text color is black,the back color is white.
SetBkColor(hdcCompatible,RGB(255,255,255));
SetTextColor(hdcCompatible,RGB(0,0,0));

// draw the text int a virtual dc.
TextOut(hdcCompatible,0,0,m\_strText,m\_strText.GetLength());

// get the text width and height.
GetTextExtentPoint32(hdcCompatible,m\_strText,m\_strText.GetLength(),&m\_sz);

// get the pixel infomation.
for(int i=0; i

the m_sz value is normal ( 8 * 16),but the color variables is invalied, because is usually is the backcolor.

( I doesn't want to draw it in the program windows and then call GetPixel function from screen,that's not so good ! :) )

why is it ,or is there any other way ?

Thans for your reply !

Best regards !

[Gwenio]

Not sure (been a while since I used GDI), but maybe you should create a compatible bitmap and select it into the device context before drawing to it?