Disable submit requests > 275,000 tiles (representing a reasonable estimation of minimum tilesize summing up to 500mb)

[rudokemper]

Closes #12.

Goal

While it is not possible to determine an actual filesize of an offline map package in advance, we can set a reasonable limit based on a minimum possible filesize of a 512px JPG, and a desired maximum MBTiles filesize limit of 500mb.

We can try this out with a "blank" tile (all white). I generated a few with mapgl-tile-renderer by downloading Planet tiles outside of the NICFI (tropical forest) AOI. The binary content stored in the MBTiles SQLite table for one such tile adds up to 18,963 bytes.

I prompted ChatGPT to run a similar estimation, arriving at a similar number:

import os
from PIL import Image

# Load the image
img = Image.open("/mnt/data/A_simple,_solid_color_image_of_a_light_blue_square.png")

# Convert to JPG with high compression (low quality setting)
compressed_image_path = "/mnt/data/compressed_high_compression.jpg"
img.save(compressed_image_path, 'JPEG', quality=5)  # Set quality low to maximize compression

# Check the file size
compressed_image_size = os.path.getsize(compressed_image_path)
compressed_image_size

Result: 18,137 bytes

Hence, we can set a tile limit in the following way (500mb in bytes divided by one minimum size JPG):

500,000,000 / 18,137 = 275679

So, we round that down to 275,000, and use that as the threshold.

Screenshots

What I changed

Disable (and change color of) submit button if estimatedTiles > 275000.