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From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.lang.c
Subject: Re: filling area by color atack safety
Date: Sun, 17 Mar 2024 19:39:08 +0200
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On Sun, 17 Mar 2024 18:25:20 +0200
Michael S <already5chosen@yahoo.com> wrote:

> On Sun, 17 Mar 2024 14:56:34 +0000
> Malcolm McLean <malcolm.arthur.mclean@gmail.com> wrote:
> 
> > On 16/03/2024 15:09, Malcolm McLean wrote:  
> > > On 16/03/2024 14:40, David Brown wrote:    
> > >> On 16/03/2024 12:33, Malcolm McLean wrote:
> > >>    
> > >>> And here's some code I wrote a while ago. Use that as a pattern.
> > >>> But not sure how well it works. Haven't used it for a long time.
> > >>>
> > >>> https://github.com/MalcolmMcLean/binaryimagelibrary/blob/master/drawbinary.c
> > >>>    
> > >>
> > >> Your implementation is a mess, /vastly/ more difficult to prove 
> > >> correct than the OP's original one, and unlikely to be very much 
> > >> faster (it will certainly scale in the same way in both time and 
> > >> memory usage).
> > >>    
> > > Now is this David Brown being David Borwn, ot its it actaully
> > > ture? 
> >   
> > > And I need to run some tests, don't I?
> > >     
> > #include <stdio.h>
> > #include <stdlib.h>
> > #include <string.h>
> > #include <time.h>
> > 
> > int floodfill_r(unsigned char *grey, int width, int height, int x,
> > int y, unsigned char target, unsigned char dest)
> > {
> >     if (x < 0 || x >= width || y < 0 || y >= height)
> >       return 0;
> >     if (grey[y*width+x] != target)
> >       return 0;
> >     grey[y*width+x] = dest;
> >     floodfill_r(grey, width, height, x - 1, y, target, dest);
> >     floodfill_r(grey, width, height, x + 1, y, target, dest);
> >     floodfill_r(grey, width, height, x, y - 1, target, dest);
> >     floodfill_r(grey, width, height, x, y + 1, target, dest);
> > 
> >     return 0;
> > }
> > 
> > /**
> >    Floodfill4 - floodfill, 4 connectivity.
> > 
> >    @param[in,out] grey - the image (formally it's greyscale but it
> > could be binary or indexed)
> >    @param width - image width
> >    @param height - image height
> >    @param x - seed point x
> >    @param y - seed point y
> >    @param target - the colour to flood
> >    @param dest - the colur to replace it by.
> >    @returns Number of pixels flooded.
> > */
> > int floodfill4(unsigned char *grey, int width, int height, int x,
> > int y, unsigned char target, unsigned char dest)
> > {
> >    int *qx = 0;
> >    int *qy = 0;
> >    int qN = 0;
> >    int qpos = 0;
> >    int qcapacity = 0;
> >    int wx, wy;
> >    int ex, ey;
> >    int tx, ty;
> >    int ix;
> >    int *temp;
> >    int answer = 0;
> > 
> >    if(grey[y * width + x] != target)
> >      return 0;
> >    qx = malloc(width * sizeof(int));
> >    qy = malloc(width * sizeof(int));
> >    if(qx == 0 || qy == 0)
> >      goto error_exit;
> >    qcapacity = width;
> >    qx[qpos] = x;
> >    qy[qpos] = y;
> >    qN = 1;
> > 
> >    while(qN != 0)
> >    {
> >      tx = qx[qpos];
> >      ty = qy[qpos];
> >      qpos++;
> >      qN--;
> > 
> >      if(qpos == 256)
> >      {
> >        memmove(qx, qx + 256, qN*sizeof(int));
> >        memmove(qy, qy + 256, qN*sizeof(int));
> >        qpos = 0;
> >      }
> >      if(grey[ty*width+tx] != target)
> >        continue;
> >      wx = tx;
> >      wy = ty;
> >      while(wx >= 0 && grey[wy*width+wx] == target)
> >        wx--;
> >      wx++;
> >      ex = tx;
> >      ey = ty;
> >      while(ex < width && grey[ey*width+ex] == target)
> >        ex++;
> >      ex--;
> > 
> > 
> >      for(ix=wx;ix<=ex;ix++)
> >      {
> >        grey[ty*width+ix] = dest;
> >        answer++;
> >      }
> > 
> >      if(ty > 0)
> >        for(ix=wx;ix<=ex;ix++)
> >        {
> > 	    if(grey[(ty-1)*width+ix] == target)
> > 	    {
> >            if(qpos + qN == qcapacity)
> > 	      {
> >              temp = realloc(qx, (qcapacity + width) * sizeof(int));
> >              if(temp == 0)
> >                goto error_exit;
> >              qx = temp;
> >              temp = realloc(qy, (qcapacity + width) * sizeof(int));
> >              if(temp == 0)
> >                goto error_exit;
> >              qy = temp;
> >              qcapacity += width;
> > 	      }
> >            qx[qpos+qN] = ix;
> >            qy[qpos+qN] = ty-1;
> >            qN++;
> > 	    }
> >        }
> >      if(ty < height -1)
> >        for(ix=wx;ix<=ex;ix++)
> >        {
> >          if(grey[(ty+1)*width+ix] == target)
> > 	    {
> >            if(qpos + qN == qcapacity)
> > 	      {
> >              temp = realloc(qx, (qcapacity + width) * sizeof(int));
> >              if(temp == 0)
> >                goto error_exit;
> >              qx = temp;
> >              temp = realloc(qy, (qcapacity + width) * sizeof(int));
> >              if(temp == 0)
> >                goto error_exit;
> >              qy = temp;
> >              qcapacity += width;
> > 	      }
> >            qx[qpos+qN] = ix;
> >            qy[qpos+qN] = ty+1;
> >            qN++;
> > 	    }
> >        }
> >    }
> > 
> >    free(qx);
> >    free(qy);
> > 
> >    return answer;
> >   error_exit:
> >    free(qx);
> >    free(qy);
> >    return -1;
> > }
> > 
> > int main(void)
> > {
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