Simple tileset generator that was useful and good practice to write.

simple_tilegen.py

# generate dem tiles
# author: Patrick Traynor 9/8/14

# Generates a tileset image from a source image of the solid, edge, outside
# corner, and inside corner sub-tiles (mini or corner tiles). Sub-tiles are
# rotated, as opposed to supplying variations of each sub-tile for each
# orientation.
# I hope somebody finds use of this script or draws some inspiration from it
# or something. It was useful to me, so I figured I may as well share it.

import sys
from PIL import Image

usage = "Usage: python " + sys.argv[0] + " sourceimage destimage\n + " + """
Image names are relative to current directory and do not include extension.
Source image must be a PNG where width = 4 * height.
__________________________________
|        --------r-------@       |
| solid    edge  |outside inside |
|                |corner  corner |
|________________|_______________|

 [      ][      ][      ][      ] """
if len(sys.argv) != 3:
  print(usage)
  exit(1)
try:
  sourceImage = Image.open(sys.argv[1] + ".png")
except:
  print("No file named " + sys.argv[1] + ".png.")
  exit(1)
if sourceImage.size[0] != sourceImage.size[1] * 4:
  print("Source image must have dimensions such that witdh = 4 * height")
  exit(1)

# crop a tile
def c(im, x, y):
  return im.crop((x * ts, y * ts, (x + 1) * ts, (y + 1) * ts))

# paste a tile
def p(im, x, y):
  output.paste(im, (x * ts, y * ts))

# paste 4 tiles in a square
def pt(imul, imur, imbl, imbr, x, y):
  p(imul, x, y)
  p(imur, x + 1, y)
  p(imbl, x, y + 1)
  p(imbr, x + 1, y + 1)

# rotate and paste 4 tiles in a square at the end of the current row
def ptcr(imul, rul, imur, rur, imbl, rbl, imbr, rbr):
  global currentx
  pt(imul.rotate(rul), imur.rotate(rur), imbl.rotate(rbl), imbr.rotate(rbr),
     currentx, currenty)
  currentx += 2

# start pasting in a new row
def newline():
  global currentx, currenty
  currenty += 2
  currentx = 0

ts = sourceImage.size[1]
output = Image.new("RGBA", (8 * ts, 10 * ts))

solid = c(sourceImage, 0, 0)
edge = c(sourceImage, 1, 0)
outcorner = c(sourceImage, 2, 0)
incorner = c(sourceImage, 3, 0)

up = 0
left = 90
down = 180
right = 270

currentx = 0
currenty = 0

ptcr(outcorner, up, edge, up, edge, left, solid, up)
ptcr(edge, up, edge, up, solid, up, solid, up)
ptcr(edge, up, outcorner, right, solid, up, edge, right)
ptcr(outcorner, up, outcorner, right, edge, left, edge, right)
newline()
ptcr(edge, left, solid, up, edge, left, solid, up)
ptcr(solid, up, solid, up, solid, up, solid, up)
ptcr(solid, up, edge, right, solid, up, edge, right)
ptcr(edge, left, edge, right, edge, left, edge, right)
newline()
ptcr(edge, left, solid, up, outcorner, left, edge, down)
ptcr(solid, up, solid, up, edge, down, edge, down)
ptcr(solid, up, edge, right, edge, down, outcorner, down)
ptcr(edge, left, edge, right, outcorner, left, outcorner, down)
newline()
ptcr(outcorner, up, edge, up, outcorner, left, edge, down)
ptcr(edge, up, edge, up, edge, down, edge, down)
ptcr(edge, up, outcorner, right, edge, down, outcorner, down)
ptcr(outcorner, up, outcorner, right, outcorner, left, outcorner, down)
newline()
ptcr(incorner, up, solid, up, solid, up, solid, up)
ptcr(solid, up, incorner, right, solid, up, solid, up)
ptcr(solid, up, solid, up, incorner, left, solid, up)
ptcr(solid, up, solid, up, solid, up, incorner, down)

try:
  output.save(sys.argv[2] + ".png")
except:
  print("Unable to write file named " + sys.argv[2] + ".png.")
  exit(1)