HOWTO: Detect If a Color Is a Dithered Color

ID: Q139201

The information in this article applies to:

Microsoft Windows Software Development Kit (SDK), used with:
- Microsoft Windows 3.1
Microsoft Win32 Application Programming Interface (API), used with:
- Microsoft Windows NT, versions 3.5, 3.51
- Microsoft Windows versions 95, 4.0
- Microsoft Win32s versions 1.2, 1.25a, 1.3
Microsoft Windows 2000

SUMMARY

When you use a COLORREF (color) to draw into a display context (DC), sometimes you need to ensure that the color is a solid color rather than a dithered color.

MORE INFORMATION

If you need to test to see if a particular COLORREF is a solid color, you can compare the COLORREF against the return value of GetNearestColor() to see if they are equivalent.

For example, the following function returns TRUE if the COLORREF value that is passed in exists as a solid color in the specified display context:


BOOL IsSolidColor(HDC hDC, COLORREF crColor)
{
    if (crColor == GetNearestColor(hDC, crColor)) {

      // Color is solid
      return TRUE;

    } else {

      // Color is dithered
      return FALSE;

    }
}

In some operations such as creating a brush, you may want to force GDI to use a solid color. To be sure that you get a solid color, you can use the GetNearestColor() function to retrieve the solid color that best matches a specified logical color. Then use that color to create the solid brush.

For example, CreateSolidBrush(crRGB) will not guarantee a solid brush. However, CreateSolidBrush(GetNearestColor(hDC, crRGB)) will guarantee a solid brush for the device for which you passed the DC.

Additional query words: 1.20 3.10 4.00 3.50 dither colorref

Keywords : kbWinOS2000
Version : WINDOWS:1.2,1.25a,1.3,3.1,4.0,95; winnt:3.5,3.51
Platform : WINDOWS winnt
Issue type : kbhowto