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From: fir <fir@grunge.pl>
Newsgroups: comp.lang.c
Subject: filling area by color atack safety
Date: Sat, 16 Mar 2024 05:11:44 +0100
Organization: i2pn2 (i2pn.org)
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i was writing simple editor (something like paint but more custom for my 
eventual needs) for big pixel (low resolution) drawing

it showed in a minute i need a click for changing given drawed area of
of one color into another color (becouse if no someone would need to do 
it  by hand pixel by pixel and the need to change color of given element 
is very common)

there is very simple method of doing it - i men i click in given color 
pixel then replace it by my color and call the same function on adjacent 
4 pixels (only need check if it is in screen at all and if the color to 
change is that initial color

int RecolorizePixelAndAdjacentOnes(int x, int y, unsigned old_color, 
unsigned new_color)
{
   if(old_color == new_color) return 0;

   if(XYIsInScreen( x,  y))
   if(GetPixelUnsafe(x,y)==old_color)
   {
     SetPixelSafe(x,y,new_color);
     RecolorizePixelAndAdjacentOnes(x+1, y,  old_color, new_color);
     RecolorizePixelAndAdjacentOnes(x-1, y,  old_color, new_color);
     RecolorizePixelAndAdjacentOnes(x, y-1,  old_color, new_color);
     RecolorizePixelAndAdjacentOnes(x, y+1,  old_color, new_color);
     return 1;
   }

   return 0;
}

it work but im not quite sure how to estimate the safety of this  - 
incidentally as i said i use this editor to low res graphics  like 
200x200 pixels or less, and it is only a toll of private use,
yet i got no time to work on it more than 1-2-3 days i guess but still

is there maybe simple way to improve it?