901210 - how CreateCompatibleDC works?

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in the following code:

C++

CDC memDC;
memDC.CreateCompatibleDC(NULL);
CBitmap bmp;
bmp.CreateCompatibleBitmap(&memDC, 100, 100);
memDC.SelectObject(&bmp);

memDC gets a monochrome DC. why?
i expect CreateCompatibleDC creates a color DC like the screen!
if i change the code into:

C++

CDC memDC;
memDC.CreateCompatibleDC(NULL);
CBitmap bmp;
CClientDC dc(NULL);
bmp.CreateCompatibleBitmap(&dc, 100, 100);
memDC.SelectObject(&bmp);

memDC gets a color DC!
how can u describe it?
thx

Posted 28-Feb-12 21:17pm

ilostmyid2

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tolw · Accepted Answer · 2012-02-28T21:24:00

Have a look at the description of CreateCompatibleBitmap[^]:

"Note: When a memory device context is created, it initially has a 1-by-1 monochrome bitmap selected into it. If this memory device context is used in CreateCompatibleBitmap, the bitmap that is created is a monochrome bitmap. To create a color bitmap, use the HDC that was used to create the memory device context, as shown in the following code:"