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/* $Id: bresenhm.c,v 1.1 1996/09/13 01:38:16 brianp Exp $ */
/*
* Mesa 3-D graphics library
* Version: 2.0
* Copyright (C) 1995-1996 Brian Paul
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* $Log: bresenhm.c,v $
* Revision 1.1 1996/09/13 01:38:16 brianp
* Initial revision
*
*/
#include "bresenhm.h"
#include "types.h"
/*
* Evaluate Bresenham's integer line drawing algorithm. Put each
* coordinate generated into x[] and y[] arrays.
*
* Input: x1,y1 - coordinates of first endpoint
* x2,y2 - coordinates of second endpoint
* Output: x, y - array of coordinates generated by the algorithm
* Return: number of values put into x[] and y[].
*/
GLuint gl_bresenham( GLcontext* ctx, GLint x1, GLint y1, GLint x2, GLint y2,
GLint x[], GLint y[] )
{
register GLint dx, dy, xf, yf, a, b, c, i;
if (x2>x1) {
dx = x2-x1;
xf = 1;
}
else {
dx = x1-x2;
xf = -1;
}
if (y2>y1) {
dy = y2-y1;
yf = 1;
}
else {
dy = y1-y2;
yf = -1;
}
#define PLOT( X, Y ) x[i] = X; y[i] = Y;
if (dx>dy) {
a = dy+dy;
c = a-dx;
b = c-dx;
for (i=0;i<=dx;i++) {
PLOT( x1, y1 );
x1 += xf;
if (c<0) {
c += a;
}
else {
c += b;
y1 += yf;
}
}
return dx+1;
}
else {
a = dx+dx;
c = a-dy;
b = c-dy;
for (i=0;i<=dy;i++) {
PLOT( x1, y1 );
y1 += yf;
if (c<0) {
c += a;
}
else {
c += b;
x1 += xf;
}
}
return dy+1;
}
#undef PLOT
}
/*
* Evaluate Bresenham's line algorithm with stippling.
* Input: x1, y1, x2, y2 - endpoints of line segment
* Output: x, y - arrays of pixels along the line
* mask - indicates draw/don't draw for each pixel
*/
GLuint gl_stippled_bresenham( GLcontext* ctx, GLint x1, GLint y1, GLint x2, GLint y2,
GLint x[], GLint y[], GLubyte mask[] )
{
GLint dx, dy, xf, yf, a, b, c, i;
GLushort m;
if (x2>x1) {
dx = x2-x1;
xf = 1;
}
else {
dx = x1-x2;
xf = -1;
}
if (y2>y1) {
dy = y2-y1;
yf = 1;
}
else {
dy = y1-y2;
yf = -1;
}
#define PLOT( X, Y ) \
m = 1 << ((ctx->StippleCounter/ctx->Line.StippleFactor) & 0xf); \
if (ctx->Line.StipplePattern & m) { \
mask[i] = 1; \
x[i] = X; \
y[i] = Y; \
} \
else { \
mask[i] = 0; \
} \
ctx->StippleCounter++;
if (dx>dy) {
a = dy+dy;
c = a-dx;
b = c-dx;
for (i=0;i<=dx;i++) {
PLOT( x1, y1 );
x1 += xf;
if (c<0) {
c += a;
}
else {
c += b;
y1 += yf;
}
}
return dx+1;
}
else {
a = dx+dx;
c = a-dy;
b = c-dy;
for (i=0;i<=dy;i++) {
PLOT( x1, y1 );
y1 += yf;
if (c<0) {
c += a;
}
else {
c += b;
x1 += xf;
}
}
return dy+1;
}
#undef PLOT
}
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