Cropping a BitMap.

[havoc1976]

I am writting a program and need help.
My program is suppose to take a screen shot and make it a bitmap, call it oldmap. I than would like to crop oldmap from its center with a size of 200 by 200 or 50 by 50 or whatever the user would like, and call it newmap.
I would than like to delete the oldmap and place it with the new map. I am confused on how to implement it.
Here is my code.

//////////////
bool Capture::screenshotGDI(Screenshot &screeny)
{
	HWND hwnd = FindWindowA(0, WindowName);
	if (hwnd == NULL)
	{
		cout << "ERROR: HWND not found!" << endl;
		return false;
	}

	int sWidth = GetSystemMetrics(SM_CXSCREEN);
	int sHeight = GetSystemMetrics(SM_CYSCREEN);

	HDC hdc = GetDC(0);
	HDC captureDC = CreateCompatibleDC(hdc);
	HBITMAP hBmp = CreateCompatibleBitmap(hdc, sWidth, sHeight);
	HGDIOBJ hOld = SelectObject(captureDC, hBmp);
	
	if (!BitBlt(captureDC, 0, 0, sWidth, sHeight, hdc, 0, 0, SRCCOPY | CAPTUREBLT))
	{
		cout << "ERROR: bit-block transfer failed!" << endl;
		release(hwnd, hdc, captureDC, hBmp);
		return false;
	}

	SelectObject(captureDC, hBmp);

	BITMAPINFO bmpInfo = { 0 };
	bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	if (!GetDIBits(hdc, hBmp, 0, 0, NULL, &bmpInfo, DIB_RGB_COLORS)) //get bmpInfo
	{
		cout << "ERROR: Failed to get Bitmap Info." << endl;
		release(hwnd, hdc, captureDC, hBmp);
		return false;
	}
	bmpInfo.bmiHeader.biCompression = BI_RGB;

	screeny.FreeMemory();

	int pixNo = bmpInfo.bmiHeader.biWidth *  bmpInfo.bmiHeader.biHeight;
	screeny.pixels = new RGBQUAD[pixNo];
	if (!screeny.pixels)
	{
		cout << "ERROR: Failed allocating RGBQUAD[" << pixNo << "]" << endl;
		release(hwnd, hdc, captureDC, hBmp);
		return false;
	}

	if (!GetDIBits(hdc, hBmp, 0, bmpInfo.bmiHeader.biHeight, (LPVOID)screeny.pixels, &bmpInfo, DIB_RGB_COLORS))
	{
		cout << "ERROR: Getting the bitmap buffer!" << endl;
		screeny.FreeMemory();
		release(hwnd, hdc, captureDC, hBmp);
		return false;
	}

	screeny.width = bmpInfo.bmiHeader.biWidth;
	screeny.height = bmpInfo.bmiHeader.biHeight;
	screeny.length = pixNo;

	release(hwnd, hdc, captureDC, hBmp);
	return true;
}
//////////////////

Any help on implementing what was stated would be amazing.
Thank you in advance.

[2kaud]

When posting code, please use code tags so that the code is readable. Go Advanced, select the formatted code and click '#'.

[Thread moved from non-visual c++ issues as relating to use of Windows APIs.]

[Igor Vartanov]

BitBlt(targetDC, x, y, width, height, sourceDC, ...) is what they call cropping. Start thinking from this point.