Bresenham's line algorithm

[taximania]

I'm sending data to a graphic LCD via Bluetooth.
I've only got a PlotPixel(x,y) available.

Does anybody have an example of Line(x1,x2,y1,y2)

I've googled but can't find a 'basic' algorithm, plenty in 'C' and VB,
but it's doing my head in trying to convert it.

TIA

 

[taximania]

Ok, I've managed it, sort of

Sub Draw_Line(x1,y1,x2,y2)
length = x2-x1
m = (y2-y1)/(x2-x1)
y = y1
For i = 0 To length
Plot(x1+i,Int(y))
y = y + m
Next i
End Sub

 

[agraham]

Here's the real thing, it won't leave gaps on steep lines.

Sub BresenhamLine(x0, y0, x1, y1)
  steep = False
  If Abs(y1 - y0) > Abs(x1 - x0) Then
    steep = True
    'swap(x0, y0)
    x = x0 : x0 = y0 : y0 = x      
    'swap(x1, y1)
    x = x1 : x1 = y1 : y1 = x   
  End If
  If x0 > x1 Then
    'swap(x0, x1)
    x = x0 : x0 = x1 : x1 = x            
    'swap(y0, y1)
    x =y0 : y0 = y1 : y1 = x
  End If
  deltax = Int(x1 - x0)
  deltay = Int(Abs(y1 - y0))
  error = Int(deltax / 2)
  y = y0
  If y0 < y1 Then
    ystep = 1
  Else
    ystep = -1
  End If
  For x = x0 To x1
    If steep Then plot(y,x) Else plot(x,y)
    error = error - deltay
    If error < 0 Then
      y = y + ystep
      error = error + deltax
    End If
  Next
End Sub

 

[taximania]

You never cease to amaze me Agraham.

I found this Atari Archive website Plotting - Computer Graphics.

Sin waves, circles, eliptical rose (?) etc, all work on my graphic Lcd.

My, 'Draw_line', only does 'right,up', or 'right,down'.
I'll try your code later :sign0188:

 

[taximania]

Here's the real thing, it won't leave gaps on steep lines.

After a few test, your definately right.

The attached program works best on the desktop. It does work on the device but the SIP covers the controls.

Circle shows a circle :sign0060:

Rose draws a shape :signOops:

Sin draws a sin wave :sign0148:

The subs code maybe of help

If you enter the x1,y1,x2,y2 values eg:

100,0,90,200 and 'Bres' you get a good solid line.

then try

100,0,110,200 and 'mine'

That is a huge difference.

Cheer A