+++ /dev/null
-/* $XConsortium: lines.c,v 1.2 91/10/10 11:18:21 rws Exp $ */
-/* Copyright International Business Machines, Corp. 1991
- * All Rights Reserved
- * Copyright Lexmark International, Inc. 1991
- * All Rights Reserved
- *
- * License to use, copy, modify, and distribute this software and its
- * documentation for any purpose and without fee is hereby granted,
- * provided that the above copyright notice appear in all copies and that
- * both that copyright notice and this permission notice appear in
- * supporting documentation, and that the name of IBM or Lexmark not be
- * used in advertising or publicity pertaining to distribution of the
- * software without specific, written prior permission.
- *
- * IBM AND LEXMARK PROVIDE THIS SOFTWARE "AS IS", WITHOUT ANY WARRANTIES OF
- * ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO ANY
- * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
- * AND NONINFRINGEMENT OF THIRD PARTY RIGHTS. THE ENTIRE RISK AS TO THE
- * QUALITY AND PERFORMANCE OF THE SOFTWARE, INCLUDING ANY DUTY TO SUPPORT
- * OR MAINTAIN, BELONGS TO THE LICENSEE. SHOULD ANY PORTION OF THE
- * SOFTWARE PROVE DEFECTIVE, THE LICENSEE (NOT IBM OR LEXMARK) ASSUMES THE
- * ENTIRE COST OF ALL SERVICING, REPAIR AND CORRECTION. IN NO EVENT SHALL
- * IBM OR LEXMARK BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
- * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
- * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
- * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
- * THIS SOFTWARE.
- */
- /* LINES CWEB V0003 ******** */
-/*
-:h1.LINES Module - Rasterizing Lines
-
-&author. Duaine W. Pryor, Jr. and Jeffrey B. Lotspiech (lotspiech@almaden.ibm.com)
-
-
-:h3.Include Files
-
-The included files are:
-*/
-
-#include "objects.h"
-#include "spaces.h"
-#include "regions.h"
-#include "lines.h"
-
-/*
-:h3.Functions Provided to the TYPE1IMAGER User
-
-None.
-*/
-
-/*
-:h3.Functions Provided to Other Modules
-
-This module provides the following entry point to other modules:
-*/
-
-/*SHARED LINE(S) ORIGINATED HERE*/
-
-/*
-:h3.Macros Provided to Other Modules
-
-None.
-*/
-
-/*
-:h2.StepLine() - Produces Run Ends for a Line After Checks
-
-The main work is done by Bresenham(); here we just perform checks and
-get the line so that its Y direction is always increasing:
-*/
-
-void StepLine(R, x1, y1, x2, y2)
- register struct region *R; /* region being built */
- register fractpel x1,y1; /* starting point */
- register fractpel x2,y2; /* ending point */
-{
- register fractpel dy;
-
- IfTrace4((LineDebug > 0), ".....StepLine: (%p,%p) to (%p,%p)\n",
- x1, y1, x2, y2);
-
- dy = y2 - y1;
-
-/*
-We execute the "GOING_TO" macro to call back the REGIONS module, if
-necessary (like if the Y direction of the edge has changed):
-*/
- GOING_TO(R, x1, y1, x2, y2, dy);
-
- if (dy == 0)
- return;
-
- if (dy < 0)
- Bresenham(R->edge, x2, y2, x1, y1);
- else
- Bresenham(R->edge, x1, y1, x2, y2);
- return;
-}
-/*
-:h3.Bresenham() - Actually Produces Run Ends
-
-This routine runs a Bresenham line-stepping
-algorithm. See, for example, Newman and Sproul, :hp1/Principles
-of Interactive Computer Graphics/, pp. 25-27.
-When we enter this, we
-are guaranteed that dy is positive.
-We'd like to work in 8 bit precision, so we'll define some macros and
-constants to let us do that:
-*/
-
-#define PREC 8 /* we'll keep fraction pels in 8 bit precision */
-/*
-RoundFP() rounds down by 'b' bits:
-*/
-#define RoundFP(xy,b) (((xy)+(1<<((b)-1)))>>(b))
-
-/*
-TruncFP() truncates down by 'b' bits:
-*/
-#define TruncFP(xy,b) ((xy)>>(b))
-
-
-void Bresenham(edgeP,x1,y1,x2,y2)
- register pel *edgeP; /* pointer to top of list (y == 0) */
- register fractpel x1,y1; /* starting point on line */
- register fractpel x2,y2; /* ending point on the line (down) */
-{
- register long dx,dy; /* change in x and y, in my own precision */
- register long x,y; /* integer pel starting point */
- register int count; /* integer pel delta y */
- register long d; /* the Bresenham algorithm error term */
-
- x1 = TruncFP(x1, FRACTBITS-PREC);
- y1 = TruncFP(y1, FRACTBITS-PREC);
- x2 = TruncFP(x2, FRACTBITS-PREC);
- y2 = TruncFP(y2, FRACTBITS-PREC);
-
- dx = x2 - x1;
- dy = y2 - y1;
-/*
-Find the starting x and y integer pel coordinates:
-*/
-
- x = RoundFP(x1,PREC);
- y = RoundFP(y1,PREC);
- edgeP += y;
- count = RoundFP(y2,PREC) - y;
-/*------------------------------------------------------------------*/
-/* Force dx to be positive so that dfy will be negative */
-/* this means that vertical moves will decrease d */
-/*------------------------------------------------------------------*/
- if (dx<0)
- {
- dx = -dx;
-#define P PREC
- d=(dy*(x1-(x<<P)+(1<<(P-1)))-dx*((y<<P)-y1+(1<<(P-1))))>>P;
-#undef P
- while(--count >= 0 )
- {
- while(d<0)
- {
- --x;
- d += dy;
- }
- *(edgeP++) = x;
- d -= dx;
- }
- }
- else /* positive dx */
- {
-#define P PREC
- d = (dy*((x<<P)-x1+(1<<(P-1)))-dx*((y<<P)-y1+(1<<(P-1))))>>P;
-#undef P
- while(--count >= 0 )
- {
- while(d<0)
- {
- ++x;
- d += dy;
- }
- *(edgeP++) = x;
- d -= dx;
- }
- }
-}
projects / rdpsrv / blobdiff