Python script that creates a simple Minecraft grass atlas.

create_grass_atlas.py

# this python script simply creates a simple grass atlas image.
# the atlas is used in this small minecraft renderer:
# https://github.com/mikolalysenko/regl/pull/21

import png
import os
import noise


# open file
OUT_FILE = "atlas.png"
f = open(OUT_FILE, 'wb')

w = 32
h = 32

writer = png.Writer(w, h, alpha='RGBA')

data = []

def lerp(a, b, l):
    return [int(a[0]*l + b[0]*(1.0-l)), int(a[1]*l + b[1]*(1.0-l)), int(a[2]*l + b[2]*(1.0-l)), 255   ]

# create atlas data.
i = 0
while i < w*h:

    x = (i % w)
    y = (i / w)

    s = 0.7;

    if y > 19:
        t = 0 # dirt
    else:
        t = 1 # grass

    if (x == 4 or x==5) and y == 19:
        t = 0

    if x == 0 and (y == 19 or y==18):
        t = 0

    if (x == 11 or x==12) and (y == 20 or y==21):
        t = 1

    if (x == 7) and (y == 20 or y==21):
        t = 1

    if (x == 15) and (y == 20 or y==21):
        t = 1


    if t == 0:
        n = 0.5 * (1.0 + noise.snoise2(x*s+1000.94,y*s+1000.32, 3, 0.5, 2.0))
        c = lerp([0.0, 0.0, 0.0], [170, 110, 40, 255],n  )

    else:
        n = 0.5 * (1.0 + noise.snoise2(x*s,y*s, 3, 0.5, 2.0))
        c = lerp([0.0,50.0,0.0], [0.0, 150.0,0.0],n  )

    data.extend(c)
    i = i + 1

#write to file
writer.write_array(f, data)
f.close()

# open file(only works in OSX)
os.system("open " + OUT_FILE)