+local function make_image_pigment(filename,scale)
+
+ print("Loading image pigmant from '" .. filename .. "'...")
+
+ local f = assert(io.open(filename, "rb"))
+ local data = f:read("*all")
+ f:close()
+
+ local start,_,wstr,hstr,dstr,raster =
+ string.find(data, "^P6[%s%c]+(%d+)[%s%c]+(%d+)[%s%c]+(%d+)[%s%c](.*)$")
+
+ if start ~= 1 then
+ error("Error reading image. Is it in PPM(P6) format?")
+ end
+
+ if dstr ~= "255" then
+ error("Only images with a depth of 255 are supported.")
+ end
+
+ local width = tonumber(wstr)
+ local height = tonumber(hstr)
+ local depth = tonumber(dstr)
+
+ local pixels = {}
+ local i = 1
+ for triple in string.gmatch(raster, "...") do
+ local _,_,r,g,b = string.find(triple, "(.)(.)(.)")
+ pixels[i] = {string.byte(r)/depth, string.byte(g)/depth, string.byte(b)/depth}
+ i = i + 1
+ end
+
+ print("done.")
+ print("(Read " .. tostring(#pixels) .. " pixels.)")
+
+ local pixels_per_unit = math.max(width,height)
+
+ return function(x,y)
+ local xi = math.floor(((x+0.5)*pixels_per_unit/scale)%width) + 1
+ local yi = math.floor(((y+0.5)*pixels_per_unit/scale)%height) + 1
+ local i = width*(yi-1) + xi
+ if pixels[i] == nil then
+ error("Pixel not found at xi=" .. tostring(xi) .. " yi=" .. tostring(yi))
+ end
+ return pixels[i]
+ end
+end
+
+local function make_mandelbrot_pigment(set_pigment, nonset_pigment, max_iter)