-- gradient blend in lua
--
-- and a quite strange blend,. but this was what I
-- ended up coding here

x1=0.25*width
y1=0.25*height
x2=0.75*width
y2=0.75*height

function dist(x1,y1,x2,y2)
   local dist= math.sqrt( (x2-x1)^2+(y2-y1)^2 )
   return dist
end

function blend_radial(x1,y1,x2,y2)
  local length=dist(x1,y1,x2,y2)
  local x,y

  print(x1,y1,x2,y2)
  
  for y = 0, height-1 do
    for x = 0, width-1 do
      local v=dist(x,y,x2,y2)/length
      set_value(x,y, v)
    end
    progress(y/height)
  end
end

function blend_strange(x1,y1,x2,y2)
  local length=dist(x1,y1,x2,y2)
  local x,y
  for y = 0, height-1 do
    for x = 0, width-1 do
      local tostart=dist(x,y,x1,y1)
      local toend=dist(x,y,x2,y2)
      local sum=tostart+toend
      local v=tostart/sum
      set_value(x,y, v)
    end
    progress(y/height)
  end
end

-- pippin didn't bother sitting down with pen paper
-- and think about the right math for this,.. thus ended up
-- without a real linear blend

blend_strange(x1,y1,x2,y2)