Advanced MFC Programming

Chapter 8. DC, Pen, Brush and Palette
User can avoid color approximation by increasing the color depth of the system. One simple way to do
so is to reduce the screen resolution (e.g. from 1024×768 to 800×600): after the total number of pixels is
reduced, the number of colors supported by the system will probably increase.
As a programmer, we need to prepare for the worst situation and make our application least susceptible
to the system setting. To achieve this, we need to implement local palette.
Figure 8-5 Dithering effect
Figure 8-6. Use nearest color for color approximation
8.8 Logical Palette
Palette
Palette is another type of GDI objects, it encapsulates a color palette that can be used to store custom
colors in an application. Although programmer can use logical palette like using an actual palette, it is not a
real palette. Within any system, there is only one existing palette, which is the physical palette (or system
palette). This is why the palettes created in the applications are called logical palettes. The advantage of
using a logical palette is that the colors defined in the logical palette can be mapped to the system palette in
an efficient way so that least color distortion can be achieved. There is no guarantee that all the colors
implemented in the logical palette will be displayed without color distortion. Actually, the ultimate color
realizing ability depends on the hardware. For example, if our hardware support only 256 colors and we
implement a 512 logical palette, some colors defined in the logical palette will inevitably be distorted if we
display all the 512 colors on the screen at the same time.
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