require"imlua"
local filename = "lena.jpg"
local image = im.FileImageLoad(filename)
local r = image[0]
local g = image[1]
local b = image[2]
for row = 0, image:Height() - 1, 10 do
for column = 0, image:Width() - 1, 10 do
r[row][column] = 0
g[row][column] = 0
b[row][column] = 0
end
end
image:Save("lena_indexing.bmp", "BMP")