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