I have written some c++ code to capture a window to a .bmp file.
BITMAPFILEHEADER get_bitmap_file_header(int width, int height)
{
BITMAPFILEHEADER hdr;
memset(&hdr, 0, sizeof(BITMAPFILEHEADER));
hdr.bfType = ((WORD) ('M' << 8) | 'B'); // is always "BM"
hdr.bfSize = 0;//sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + (width * height * sizeof(int));
hdr.bfReserved1 = 0;
hdr.bfReserved2 = 0;
hdr.bfOffBits = (DWORD)(sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER));
return hdr;
}
BITMAPINFO get_bitmap_info(int width, int height)
{
BITMAPINFO bmi;
memset(&bmi.bmiHeader, 0, sizeof(BITMAPINFOHEADER));
//initialize bitmap header
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biWidth = width;
bmi.bmiHeader.biHeight = height;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 4 * 8;
bmi.bmiHeader.biCompression = BI_RGB;
bmi.bmiHeader.biSizeImage = width * height * 4;
return bmi;
}
void get_bitmap_from_window(HWND hWnd, int * imageBuff)
{
HDC hDC = GetWindowDC(hWnd);
SIZE size = get_window_size(hWnd);
HDC hMemDC = CreateCompatibleDC(hDC);
RECT r;
HBITMAP hBitmap = CreateCompatibleBitmap(hDC, size.cx, size.cy);
HBITMAP hOld = (HBITMAP)SelectObject(hMemDC, hBitmap);
BitBlt(hMemDC, 0, 0, size.cx, size.cy, hDC, 0, 0, SRCCOPY);
//PrintWindow(hWnd, hMemDC, 0);
BITMAPINFO bmi = get_bitmap_info(size.cx, size.cy);
GetDIBits(hMemDC, hBitmap, 0, size.cy, imageBuff, &bmi, DIB_RGB_COLORS);
SelectObject(hMemDC, hOld);
DeleteDC(hMemDC);
ReleaseDC(NULL, hDC);
}
void save_image(HWND hWnd, char * name)
{
int * buff;
RECT r;
SIZE size;
GetWindowRect(hWnd, &r);
size.cx = r.right-r.left;
size.cy = r.bottom-r.top;
buff = (int*)malloc(size.cx * size.cy * sizeof(int));
get_bitmap_from_window(hWnd, buff);
BITMAPINFO bmi = get_bitmap_info(size.cx, size.cy);
BITMAPFILEHEADER hdr = get_bitmap_file_header(size.cx, size.cy);
FILE * fout = fopen(name, "w");
fwrite(&hdr, 1, sizeof(BITMAPFILEHEADER), fout);
fwrite(&bmi.bmiHeader, 1, sizeof(BITMAPINFOHEADER), fout);
fwrite(buff, 1, size.cx * size.cy * sizeof(int), fout);
fflush(fout);
fclose(fout);
free(buff);
}
It works find under XP, but under Vista the border of the window is transparent.
Using PrintWindow solves the problem, but is unacceptable for performance reasons.
Is there a performant code change, or a setting that can be changed to make the border non-transparent?
