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[Previous](36-03.html) [Table of Contents](index.html) [Next](37-01.html)
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Notwithstanding that it’s not optimized, Listing 36.1 is reasonably
fast. If you run Listing 36.2 (a sample line-drawing program that you
can use to test-drive Listing 36.1), you may be as surprised as I was at
how quickly the screen fills with vectors, considering that Listing 36.1
is entirely in C and has some redundant divides. Or perhaps you won’t be
surprised—in which case I suggest you *not* miss the next chapter.
**LISTING 36.2 L36-2.C**
/* Sample line-drawing program. Uses the optimized
line-drawing functions coded in LListing L36.1.C.
Tested with Borland C++ in the small model. */
#include <dos.h>
#define GRAPHICS_MODE 0x13
#define TEXT_MODE 0x03
#define BIOS_VIDEO_INT 0x10
#define X_MAX 320 /* working screen width */
#define Y_MAX 200 /* working screen height */
extern void LineDraw(int XStart, int YStart, int XEnd, int YEnd, int Color);
/* Subroutine to draw a rectangle full of vectors, of the specified
* length and color, around the specified rectangle center. */
void VectorsUp(XCenter, YCenter, XLength, YLength, Color)
int XCenter, YCenter; /* center of rectangle to fill */
int XLength, YLength; /* distance from center to edge of rectangle */
int Color; /* color to draw lines in */
{
int WorkingX, WorkingY;
/* lines from center to top of rectangle */
WorkingX = XCenter - XLength;
WorkingY = YCenter - YLength;
for ( ; WorkingX < ( XCenter + XLength ); WorkingX++ )
{
LineDraw(XCenter, YCenter, WorkingX, WorkingY, Color);
}
/* lines from center to right of rectangle */
WorkingX = XCenter + XLength - 1;
WorkingY = YCenter - YLength;
for ( ; WorkingY < ( YCenter + YLength ); WorkingY++ )
{
LineDraw(XCenter, YCenter, WorkingX, WorkingY, Color);
}
/* lines from center to bottom of rectangle */
WorkingX = XCenter + XLength - 1;
WorkingY = YCenter + YLength - 1;
for ( ; WorkingX >= ( XCenter - XLength ); WorkingX-- )
{
LineDraw(XCenter, YCenter, WorkingX, WorkingY, Color);
}
/* lines from center to left of rectangle */
WorkingX = XCenter - XLength;
WorkingY = YCenter + YLength - 1;
for ( ; WorkingY >= ( YCenter - YLength ); WorkingY-- )
{
LineDraw(XCenter, YCenter, WorkingX, WorkingY, Color);
}
}
/* Sample program to draw four rectangles full of lines. */
int main()
{
union REGS regs;
/* Set graphics mode */
regs.x.ax = GRAPHICS_MODE;
int86(BIOS_VIDEO_INT, &regs, &regs);
/* Draw each of four rectangles full of vectors */
VectorsUp(X_MAX / 4, Y_MAX / 4, X_MAX / 4, Y_MAX / 4, 1);
VectorsUp(X_MAX * 3 / 4, Y_MAX / 4, X_MAX / 4, Y_MAX / 4, 2);
VectorsUp(X_MAX / 4, Y_MAX * 3 / 4, X_MAX / 4, Y_MAX / 4, 3);
VectorsUp(X_MAX * 3 / 4, Y_MAX * 3 / 4, X_MAX / 4, Y_MAX / 4, 4);
/* Wait for a key to be pressed */
getch();
/* Return back to text mode */
regs.x.ax = TEXT_MODE;
int86(BIOS_VIDEO_INT, &regs, &regs);
}
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[Previous](36-03.html) [Table of Contents](index.html) [Next](37-01.html)
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* * * * *
Graphics Programming Black Book © 2001 Michael Abrash