| This sample is derived from the VMSAMP.C sample (available
on your DOS distribution disk). VMSAMP.C illustrates the use of the VESAMENU
library including constructing and calculating the sizes of menus. It
can be used as the starting point for an application.
This sample adds to the VMSAMP sample by illustrating how
to use color with a monochrome frame grabber and a monochrome VESAMENU
library.
There are two topics illustrated in this sample:
- Drawing a color overlay on a monochrome image.
- Producing color menus
Drawing a color overlay on a monochrome image:
In order to draw a color overlay on a monochrome image,
you need to give up a few of the colors in the image. See the PX User
Manual section on the input LUT. The LUT accepts 256 digitized values
from the A/D converter. It produces 256 gray values according to the values
it has been programmed with. Normally, the LUT is programmed with the
values from 0 to 255. However, if you skip a few of those values, then
you can convert those values to color on the VGA screen. For example,
if you program the LUT such that the offsets 1, 2, and 3 all have the
value of 0, then the LUT will not produce the values of 1, 2, and 3 since
those values have not been programmed into the LUT.
Normally the first 5 entries in the LUT would look like
this:
0, 1, 2, 3, 4
However, in the above example the first 5 entries would look
like this:
0, 0, 0, 0, 4
Remember that this removes the values 1, 2, and 3 from your
image. If you absolutely need all 256 gray values in your image, then
you cannot afford to do this.
See Item 1 in the source code for an example of programming
the first three offsets in the LUT.
In order to draw a color overlay using the 3 values you
have deleted from the LUT, you would need to set those values to RED,
GREEN, and BLUE or any other colors. See the function SetPalette below.
The last thing is to draw the rectangles using draw_rectangle().
The rectangles will appear in the color you choose.
Producing color menus:
The VESAMENU library provides a mechanism for setting the
colors of menus, menu backgrounds, etc. VESAMENU exports a global variable
called "colors". It contains 8 values that can be set, see Item 2 below.
Also see Chapter 6 in the PX User Manual. The section on Menu Structures
and Types defines the structure of colors.
Compile as follows:
Borland and Turbo:
bcc -ml pxcolor.c px5_lb.lib vmenu_lb.lib
tcc -ml pxcolor.c px5_lb.lib vmenu_lb.lib
Microsoft version 7.0 or later:
cl /AL pxcolor.c px5_lm.lib vmenu_lm.lib
Microsoft before version 7.0:
cl /AL pxcolor.c px5_l6.lib vmenu_l6.lib
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