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From: fir <fir@grunge.pl>
Newsgroups: comp.lang.c
Subject: Re: filling area by color atack safety
Date: Wed, 20 Mar 2024 00:03:04 +0100
Organization: i2pn2 (i2pn.org)
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Michael S 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)
>> {
>>      unsigned char *image;
>>      clock_t tick, tock;
>>      int i;
>>
========== REMAINDER OF ARTICLE TRUNCATED ==========