--
-- grid.lua
--
--

require "gd"

imgX = 950;
imgY = 550;

im	= gd.createTrueColor(  imgX, imgY  )

color   = im:colorAllocateAlpha( 255, 255, 255, 64)
color2  = im:colorAllocateAlpha( 255, 255, 255, 32)


im:filledRectangle(  0,0, imgX,imgY, color2 )

--[==[
im:filledRectangle(  10,10,95,95,color2 )
im:filledRectangle(  105,105,190,190,color )
im:line(100,10,100,190,color)
im:line(10,100,190,100,color2)
im:rectangle( 5,5,195,195,color2 )
]==]


--[==[
==
== grid draws horizontal and vertical lines.
==      It adds minor ticks inside each edge and in the middle
]==]
function grid( minx,miny,maxx,maxy,incx,incy,incmx,incmy )
  if incx > 0 then
    midy = (maxy+miny)/2
    ofsx = minx
    while( ofsx < maxx+1 ) do
      im:line(ofsx,miny,ofsx,maxy,color)
      ofsx = ofsx + incx
	end

	im:line(minx,midy,maxx,midy,color)


    ofsx = minx
    while( ofsx < maxx+1 ) do
      im:line(ofsx,miny,ofsx,miny+5,color)
      im:line(ofsx,midy-5,ofsx,midy+5,color)
      im:line(ofsx,maxy-5,ofsx,maxy,color)
      ofsx = ofsx + incmx
	end
  end

  if incy > 0 then
    midx = (maxx+minx)/2

    ofsy = miny
    while( ofsy < maxy+1 ) do
      im:line(minx,ofsy,maxx,ofsy,color)
      ofsy = ofsy + incy
	end

	im:line(midx,miny,midx,maxy,color)


    ofsy = miny
    while( ofsy < maxy+1 ) do
      im:line(minx,ofsy,minx+5,ofsy,color)
      im:line(midx-5,ofsy,midx+5,ofsy,color)
      im:line(maxx-5,ofsy,maxx,ofsy,color)
      ofsy = ofsy + incmy
	end
  end
end


grid(25,25,imgX-25,imgY-25,50,50,10,10)


im:jpeg( "grid.jpg",90 )
im:png(  "grid.png",90 )