Crop multiple images from single image

Question

This code works alright, but it's very difficult to get the dimensions right and takes a bunch of trial and error. I'm wondering how I could improve it. It's meant to cut up board game pieces from a single sheet to then be used for Vassal modules.

It takes a counter sheet (I'll provide a link with an example) and cuts out / exports the individual pieces to be used by another program, which requires each piece to have its own image.

This is an example of a typical countersheet:

https://cf.geekdo-images.com/images/pic312586_md.jpg

############################################
#
#
# WARGAME COUNTER-CUTTER
# Programmed by Ray Weiss
# [email protected]
#
#
############################################
# imports
import os
from PIL import Image
from sys import argv
save_dir = "results"
filename = argv[1] # Your counter sheet
img = Image.open(filename)
if not os.path.exists(save_dir):
 os.makedirs(save_dir)
coord_input = input("Enter coordinates of first cell x, y: ")
start_pos = start_x, start_y = [int(x) for x in coord_input.split(",")]
counter_input = input("Enter the size of the counters x, y: ")
counter_size = w, h = [int(x) for x in counter_input.split(",")]
major_columns = int(input("Number of Pages: "))
major_columns_w = int(input("Width between cell to cell on the next page: "))
major_rows = int(input("Number of blocks per page: "))
major_rows_h = int(input("height between cell to cell on the next block: "))
columns = int(input("Number of columns inside a block: "))
rows = int(input("Number of rows inside a block: "))
###################################
#
# End of user supplied arguments
# Start of program
#
###################################
frame_num = 1
w, h = counter_size
for col_m in range(major_columns):
 for row_m in range(major_rows):
 for row in range(rows):
 for col in range(columns):
 x = w * col + start_x + major_columns_w * col_m
 y = h * row + start_y + major_rows_h * row_m
 crop = img.crop((x, y, x + w, y + h))
 save_at_template = os.path.join(save_dir, "counter_{:03}.png")
 crop.save(save_at_template.format(frame_num))
 frame_num += 1

• lerugray: Yeah sure, what it does, is takes a countersheet (ill provide a link with an example) and cuts out / exports the individual pieces to be used by another program, which requires each piece to have its own image. this is an example of a typical countersheet cf.geekdo-images.com/images/pic312586_md.jpg
• Ludisposed: If you could edit this in the question, that would be great ^^
• lerugray: Right now, it works but it's difficult to get the exact dimensions, so the images are often off center and unaligned, wondering if there is maybe a better way to do so.
• lerugray: this is true, what is opencv? how would I use it?

Answer 1

The images are often off center and unaligned

• That is because those images are probably not 100% accurate compared to the user_input.

You could make use of something like opencv to find the individual pieces. Afterwards you can crop and save those pieces. This will be a big improvement as you could give it a different image, and it would create individual pieces from it... no more measurement from the user!

• lerugray: if anyone good with opencv could suggest how I would go about using it above, I would very much appreciate it!
• Ludisposed: @lerugrat Sorry, code not yet written falls out of scope of this site. I suggest reading some of the tutorials I linked to, or searching on SO

Answer 2

I at least figured out a way to debug the original quicker, instead of asking for input, it just reads it from an txt file, im sure there is a better way read each line but here is what i ended up grokking.

############################################
#
#
# WARGAME COUNTER-CUTTER
# Programmed by Ray Weiss
# [email protected]
#
#
############################################
# imports
import os
from PIL import Image
from sys import argv
save_dir = "results"
filename = argv[1] # Your counter sheet
img = Image.open(filename)
if not os.path.exists(save_dir):
 os.makedirs(save_dir)
with open("instr.txt") as f:
 lines = f.readlines()
start_pos = start_x, start_y = [int(x) for x in lines[0].split(",")]
counter_size = w, h = [int(x) for x in lines[1].split(",")]
major_columns = int(lines[2])
major_columns_w = int(lines[3])
major_rows = int(lines[4])
major_rows_h = int(lines[5])
columns = int(lines[6])
rows = int(lines[7])
###################################
#
# End of user supplied arguments
# Start of program
#
###################################
frame_num = 1
w, h = counter_size
for col_m in range(major_columns):
 for row_m in range(major_rows):
 for row in range(rows):
 for col in range(columns):
 x = w * col + start_x + major_columns_w * col_m
 y = h * row + start_y + major_rows_h * row_m
 crop = img.crop((x, y, x + w, y + h))
 save_at_template = os.path.join(save_dir, "counter_{:03}.png")
 crop.save(save_at_template.format(frame_num))
 frame_num += 1