-- random neighbor
-- take random pixel value from current pixel neighbour and replace current pixel 
-- with random pixel if difference of original and random luminance is less then tolerance
-- author: Sinisa Petric, (pixopedia@sigmapi-design.com), 2008
-- uses Pixopedia_24 vars and functions for images

image_OUT = 0
image_INP = 1


seed_window = 9
seed_retries = 3

lum_tol = 40/255.0

-- get random pixel from neighborhood and check the luminance 

function get_random_rgb(x, y, window, retries)
   local rand_x, rand_y, r, g, b, lum1, lum2
   r, g, b = fp24_getImageRGB(image_INP, x, y)    
   for k = 0, retries do
      rand_x =  x + math.floor((math.random(window + 1) - 1) - window/2) 
      rand_y =  y + math.floor((math.random(window + 1) - 1) - window/2)        
      lum1 = fp24_getImageLuminance01(image_INP, rand_x, rand_y)      
      lum2 = fp24_getImageLuminance01(image_INP, x, y)      
      if math.abs(lum1 - lum2) < lum_tol then
         r, g, b = fp24_getImageRGB(image_INP, rand_x, rand_y)    
         break
      end   
   end
   return r, g, b
end

-- main routine

math.randomseed( os.time() )
for y = 0, vp24_height-1 do
    for x = 0, vp24_width-1 do
        r,g,b = get_random_rgb(x,y, seed_window, seed_retries)
        fp24_setImageRGB(image_OUT, x, y, r, g, b)        
    end
    fp24_showProgress(y, vp24_height)
end