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 line algorithm help  (Read 779 times) 0 Members and 1 Guest are viewing this topic.
zulo

Junior Devvie

Java games rock!

 « Posted 2005-02-14 19:46:51 »

I use bufferedimage and have methods to
put a pixel in the image ( edit a value in the array), and i have a myDrawLine(int x,int y) method that draws a line using the pixel method. However it doesnt work as expected, the line drawn has space in it..can someone post an algorithm for drawing a line just by filling in the pixels representing the line?

this is for the 4k competition game im trying to make, i really would like to get this to work by myself but..:/ im not good enough

ive been looking for a basic tutorial on graphics with this kind of algorithm explained and from what i learned i created this method:

 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17 `public static void myDrawLine(int x1, int y1, int x2, int y2)            {                  int deltax = x2 - x1;           // The difference in the x's                  int deltay = y2 - y1;           // The difference in the y's                  int y = y1;                     // Start y off at the first pixel value                  int ynum = deltax / 2;          // The starting value for the numerator                  for (int x = x1; x <= x2; x++)                  {                    Point(x, y);           // Draw the current pixel                    ynum += deltay;           // Increase the numerator by the top of the fraction                    if (ynum >= deltax)       // Check if numerator >= denominator                    {                      ynum -= deltax;         // Calculate the new numerator value                      y++;                    // Increase the value in front of the numerator (y)                    }                  }}`

but the line created looks incomplete drawn at some
angles..i know this works only when the x coordinate is smaller then the x2 coordinate..

maybe i should just use the Graphics.drawline() method? would save some space probably
tom
 « Reply #1 - Posted 2005-02-14 20:12:29 »

You need 2 for loops. One that iterates vertically (y) when deltay > deltax, and one wich iterates horisontally (x) when deltay <= deltax.

oNyx

JGO Coder

Medals: 2

pixels! :x

 « Reply #2 - Posted 2005-02-14 20:44:10 »

Pick one...
 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63  64  65  66  67  68  69  70  71  72  73  74  75  76  77  78  79  80  81  82  83  84  85  86  87  88  89  90  91  92  93  94  95  96  97  98  99  100  101  102  103  104  105  106  107  108  109  110  111  112  113  114 `public void brese(Graphics g, int x0, int y0, int x1, int y1){      if(x0>x1)      {            int s=x0;            x0=x1;x1=s;            s=y0;            y0=y1;y1=s;      }      boolean steep=Math.abs(y1-y0)>Math.abs(x1-x0);      if(steep)      {            int s=x0;            x0=x1;x1=s;            s=y0;            y0=y1;y1=s;      }      int deltax=x1-x0;      int deltay=Math.abs(y1-y0);      int error=0;      int deltaerr=deltay;      int y=y0;      int ystep=y0=deltax)            {                  y+=ystep;                  error-=deltax;            }      }}public void brese2(Graphics g, int x0, int y0, int x1, int y1){      int dy = y1 - y0;      int dx = x1 - x0;      if(dx == 0 && dy == 0)            return;      double tX = x0;      double tY = y0;      if(Math.abs(dy) > Math.abs(dx))      {            int ystep = y1 <= y0 ? -1 : 1;            double d = (double)dx / (double)dy;            for(int c = 0; c <= Math.abs(dy); c++)            {                  plot(g,(int)Math.round(tX),(int)Math.round(tY));                  tX += d * (double)ystep;                  tY += ystep;            }      } else      {            int xstep = x1 <= x0 ? -1 : 1;            double d = (double)dy / (double)dx;            for(int c = 0; c <= Math.abs(dx); c++)            {                  int y = (int)Math.round(tY);                  plot(g,(int)Math.round(tX),(int)Math.round(tY));                  tY += d * (double)xstep;                  tX += xstep;            }      }}public void brese3(Graphics g, int x0, int y0, int x1, int y1){      int dy = y1 - y0;      int dx = x1 - x0;      double tX = x0;      double tY = y0;      int xstep = x1 <= x0 ? -1 : 1;      int ystep = y1 <= y0 ? -1 : 1;      double d;      boolean ys;      if(Math.abs(dy) > Math.abs(dx))      {            d = (double)dx / (double)dy;            ys = true;      }      else      {            d = (double)dy / (double)dx;            ys = false;      }      int cx=x0, cy=y0;      boolean hack=true;      do      {            if(!hack)            {                  if(ys)                  {                        tX += d * (double)ystep;                        tY += ystep;                  }                  else                  {                        tY += d * (double)xstep;                        tX += xstep;                  }                  cx=(int)Math.round(tX);                  cy=(int)Math.round(tY);            }            hack=false;            plot(g,cx,cy);      }while(cx!=x1||cy!=y1);}`

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