How to Detect the Number of Colors Available in a DC

Last reviewed: November 14, 1995
Article ID: Q139202

The information in this article applies to:

Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

Microsoft Win32 Application Programming Interface (API) included with:

    - Microsoft Windows NT versions 3.5 and 3.51
    - Microsoft Windows 95 version 4.0
    - Microsoft Win32s versions 1.2, 1.25a, and 1.3

SUMMARY

When writing an application that uses the GDI, you may sometimes need to detect how many colors are available in the current video mode.

MORE INFORMATION

If you need to detect the total number of bits that are used to form a pixel in a given display context, you can use the following algorithm:

int dBitsInAPixel = GetDeviceCaps(hdc, PLANES) *
                    GetDeviceCaps(hdc, BITSPIXEL);

To determine how many colors are available, you can raise 2 to the power of dBitsInAPixel and this will return the maximum number of colors that are displayable at a given time in the specified display context (DC).

Additional reference words: 1.20 1.30 3.10 4.00 3.50 colorref rgb bpp
KBCategory: kbprg kbhowto
KBSubcategory: W32

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Last reviewed: November 14, 1995
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