home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Libris Britannia 4
/
science library(b).zip
/
science library(b)
/
DJGPP
/
CBGRX103.ZIP
/
contrib
/
libgrx
/
src
/
scanellp.c
< prev
next >
Wrap
Text File
|
1993-12-06
|
4KB
|
134 lines
/**
** SCANELLP.C
**
** Copyright (C) 1992, Csaba Biegl
** 820 Stirrup Dr, Nashville, TN, 37221
** csaba@vuse.vanderbilt.edu
**
** This file is distributed under the terms listed in the document
** "copying.cb", available from the author at the address above.
** A copy of "copying.cb" should accompany this file; if not, a copy
** should be available from where this file was obtained. This file
** may not be distributed without a verbatim copy of "copying.cb".
** You should also have received a copy of the GNU General Public
** License along with this program (it is in the file "copying");
** if not, write to the Free Software Foundation, Inc., 675 Mass Ave,
** Cambridge, MA 02139, USA.
**
** This program 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 General Public License for more details.
**/
#include "grx.h"
#include "libgrx.h"
#include "clipping.h"
#ifdef __TURBOC__
#define MAX_R_SQUARE 120
#endif
#ifdef __GNUC__
#define MAX_R_SQUARE 32000
#endif
void _GrScanEllipse(
int xc,int yc,int xa,int ya,
int filled,
int is_XOR_color,
_GrPixelDrawProc pixelproc,
_GrLineDrawProc borderproc,
_GrScanLineProc scanfillproc,
void *fillarg)
{
int x1,x2,y1,y2;
MOUSE_FLAG;
if(xa < 0) xa = (-xa);
if(ya < 0) ya = (-ya);
x1 = xc - xa; y1 = yc - ya;
x2 = xc + xa; y2 = yc + ya;
CLIPSORTEDBOX(CURC,x1,y1,x2,y2);
MOUSE_BLOCK(CURC,x1,y1,x2,y2);
if(ya == 0) {
if(xa == 0) (*pixelproc)(xc,yc,fillarg);
else (*scanfillproc)(x1,x2,yc,fillarg);
}
else if(xa == 0) {
(*borderproc)(xc,y1,xc,y2,fillarg);
}
else if(xa > (MAX_R_SQUARE / ya)) { /* Bresenheim would overflow !! */
int points[MAX_ELLIPSE_PTS+1][2];
int numpts = _GrGenerateEllipse(points,xc,yc,xa,ya);
if(filled) _GrScanConvexPoly(numpts,points,
is_XOR_color,
pixelproc,
borderproc,
scanfillproc,
fillarg
);
else _GrDrawPolygon(numpts,points,
TRUE,
is_XOR_color,
pixelproc,
borderproc,
fillarg
);
}
else {
int yasq = ya * ya;
int xasq = xa * xa;
int xasq2 = xasq << 1;
int yasq2 = yasq << 1;
int xasq4 = xasq << 2;
int yasq4 = yasq << 2;
int row = ya;
int col = 0;
int DST = (xasq2 * (row - 1) * row) + xasq + (yasq2 * (1 - xasq));
while((xasq * row) > (yasq * col)) {
if(!filled) {
(*pixelproc)(xc-col,yc-row,fillarg);
(*pixelproc)(xc-col,yc+row,fillarg);
if(col) {
(*pixelproc)(xc+col,yc-row,fillarg);
(*pixelproc)(xc+col,yc+row,fillarg);
}
}
if(DST >= 0) {
if(filled) {
(*scanfillproc)(xc-col,xc+col,yc-row,fillarg);
(*scanfillproc)(xc-col,xc+col,yc+row,fillarg);
}
row--;
DST -= xasq4 * row;
}
DST += yasq2 * (3 + (col << 1));
col++;
}
DST = (yasq2 * (col + 1) * col) + (xasq2 * (row * (row - 2) + 1)) + ((1 - xasq2) * yasq);
while(row >= 0) {
if(!filled) {
(*pixelproc)(xc-col,yc-row,fillarg);
(*pixelproc)(xc+col,yc-row,fillarg);
if(row) {
(*pixelproc)(xc-col,yc+row,fillarg);
(*pixelproc)(xc+col,yc+row,fillarg);
}
}
else {
(*scanfillproc)(xc-col,xc+col,yc-row,fillarg);
if(row) (*scanfillproc)(xc-col,xc+col,yc+row,fillarg);
}
if(DST <= 0) {
col++;
DST += yasq4 * col;
}
row--;
DST += xasq2 * (2 - (row << 1));
}
}
MOUSE_UNBLOCK();
}