SetPixel() and DrawText() not working in 1bit per pixel bitmap

Question

SetPixel() and DrawText() not working in 1bit per pixel bitmap

I'm trying to manipulate a 1 bit per pixel bitmap created with a CreateDIBSection() call.

I call SetPixel(hDC, x, x, RGB(255, 255, 255)) and SetPixel(hDC, x, x, RGB(0, 0, 0)) but I get no changes in the bitmap.

When I check the return value it is -1 which should indicate an error, but the GetLastError() call indicates that it succeeded with no errors.

Should I be using something other than setpixel() with a 1bbp bitmap? I would prefer not to have to write my own pixel setting routines.

I've also tried a DrawText() call, it returns a height of 16, but I get no text in the bitmap.

I have manually set bits in the bitmap and that is working correctly.

Regards,
Greg

Answer 1

This test works for me with 1 bpp bitmap =>

                int nWidth = 256, nHeight = 256;  
                COLORREF clrBackground = RGB(0, 0, 255);  
                COLORREF clrForeground = RGB(255, 255, 0);  
                HBITMAP hBitmap = CreateMonochromeBitmap(nWidth, nHeight, clrBackground, clrForeground);  
                HDC hDC = GetDC(NULL);  
                HDC hDCMem = CreateCompatibleDC(hDC);                      
                HBITMAP hBitmapOld = (HBITMAP)SelectObject(hDCMem, hBitmap);  

                RECT rc = { 0, 0, nWidth, nHeight };  
                SetTextColor(hDCMem, clrForeground);  
                SetBkColor(hDCMem, clrBackground);  
                DrawText(hDCMem, L"This is a test", -1, &rc, DT_SINGLELINE | DT_CENTER | DT_VCENTER);  
                for (int i = 10; i <= nWidth - 10; i++)  
                    SetPixel(hDCMem, i, 10, clrForeground);  

                // Test copy bitmap on screen  
                BitBlt(hDC, 0, 0, nWidth, nHeight, hDCMem, 0, 0, SRCCOPY);  

                SelectObject(hDCMem, hBitmapOld);  
                DeleteDC(hDCMem);  
                DeleteObject(hBitmap);  
                ReleaseDC(NULL, hDC);  

Utility function :

HBITMAP CreateMonochromeBitmap(int cx, int cy, COLORREF clrBackground, COLORREF clrForeground)  
{  
    struct  
    {  
        BITMAPINFOHEADER bi;  
        RGBQUAD bmiColors[2];  
    } dib = { 0 };  
    dib.bi.biSize = sizeof(dib.bi);  
    dib.bi.biWidth = cx;  
    dib.bi.biHeight = cy;  
    dib.bi.biPlanes = 1;  
    dib.bi.biBitCount = 1;  
    dib.bi.biCompression = BI_RGB;   
    dib.bmiColors[0].rgbBlue = GetBValue(clrBackground);  
    dib.bmiColors[0].rgbGreen = GetGValue(clrBackground);  
    dib.bmiColors[0].rgbRed = GetRValue(clrBackground);  
    dib.bmiColors[1].rgbBlue = GetBValue(clrForeground);  
    dib.bmiColors[1].rgbGreen = GetGValue(clrForeground);  
    dib.bmiColors[1].rgbRed = GetRValue(clrForeground);  
  
    HBITMAP hBitmap = NULL;  
    HDC hDC = CreateCompatibleDC(NULL);  
    if (hDC)  
    {  
        hBitmap = CreateDIBSection(hDC, (BITMAPINFO*)&dib, DIB_RGB_COLORS, NULL, NULL, 0);  
        DeleteDC(hDC);  
    }  
    return hBitmap;  
}