What are the benefits of binary format when storing map info?

I am developing isometric 2D exploration game. At this moment I faced with a problem where game takes too much disk space. Game's world at this moment is about 1 square kilometer and it's about 50MB.

I need to somehow squeeze it. Should I think about compressing it to archive or maybe there's some kind of game files packing technique?

What about binary? Can someone explain me the magic behind it? I heard that a lot of people use it, but when I tried to use it - it took same amount of space like simple .txt file.

I'm new on file formats, so I would be grateful for any ideas. Thanks.

Answer

Use the organization of the data to your benefit. You can always be expect the data in the same order, so you know what the next bytes belong to. For example (not specific to your data), when reading in the data, always expect two bytes for tile type, two bytes for lighting information and then two bytes for extra info. So it knows that after 6 bytes, it's time to move onto the next tile. Don't store strings for your tile types, with two bytes you have many thousands of different types. It can take two bytes just to store one character depending on the format.

Don't store position information, it should be implied in the tile order. Always store the tile information in chunks, one column at a time (or one row at a time). This allows you to know the position of the next tile, without needing to read it from the byte stream. You read the starting position of the chunk, then the first tile is placed at that position. Then you know the second tile will be placed at the chunk position plus one in the Y direction (if sending column per column).

If your goal is to make the file smaller, you are probably going to have to give up the human readable feature (which is what your current formatting looks like it was designed for).

As for defining tiles as numbers. You just create a "conversion chart" in your code:

Decimal : Name     : Byte Value

0       : None     : 0000 0000
1       : Dirt     : 0000 0001
2       : Grass    : 0000 0010
3       : Snow     : 0000 0011
...
230     : Lava     : 1110 0110

If you have less than 256 different types of tiles (dirt, grass, sand, etc.), which is likely, you should just write a single byte to store the value of the tile.

When you write the data, make you're writing in a binary format. If you're writing characters as numbers, you're not doing it right. When you read the data back in, you check the byte value against your chart, and load the appropriate tile in to the game.

Look into how your language of choice can write to a byte stream, or write bytes directly. It's clear that you're writing text to your file because you have new lines for each tile. A binary format is probably going to be unreadable for your average text file editor. But your game can read it, so it doesn't matter.