Thread: Compression

I did a search in this section for compression and didn't find anything really useful for those of you who would like to compress a map file here is some code that may help you out.

Code:

ifstream asd;
		int counter = -1, data= 0, olddata,sets=0;
		asd.open("game.dat");
		data = mymap[0][0];
		olddata = data;
		for(h = 0;h < 50;h++)
		{
			for(w = 0;w < 100;w++)
			{
				counter++;
				data = mymap[w][h];
				if(data != olddata)
				{
					asd<<counter<<" "<<olddata<<endl;
					counter=0;
				}
				olddata = data;
			}
		}
		asd<<"999999";
		asd.close();

here is a simple walkthrough of how this works.
1) Im assuming you have your map loaded into the array mine is 100x50 squares and have incuded fstream.h
2) we set the counter of repetitions to -1 because this code offsets it easy fix actually but i was just tring to get it to work at the time.
3) we loop for a while counting how many times we see the same number in a row. then we save the count and what tile it was to the file and start on the new one.
4) we keep doing that till we are done.

Ive obtained a 40% encryption on my map which is suitable atm. if you use alot of different tiles in your maps you may not want to use this because if the number of different tiles > 50% of your map size you will be lucky to break even. But for maps with water and somewhat open areas this compression can save alot of file space. In very extreme cases you can have nearly 99.9% compression to -100% compression (tile changes every time)

Hope this helps someone. Also note 999999 is just my way of saying "end" change to your liking

Originally Posted by ~Kyo~

I did a search in this section for compression and didn't find anything really useful for those of you who would like to compress a map file here is some code that may help you out.

Code:

ifstream asd;
		int counter = -1, data= 0, olddata,sets=0;
		asd.open("game.dat");
		data = mymap[0][0];
		olddata = data;
		for(h = 0;h < 50;h++)
		{
			for(w = 0;w < 100;w++)
			{
				counter++;
				data = mymap[w][h];
				if(data != olddata)
				{
					asd<<counter<<" "<<olddata<<endl;
					counter=0;
				}
				olddata = data;
			}
		}
		asd<<"999999";
		asd.close();

here is a simple walkthrough of how this works.
1) Im assuming you have your map loaded into the array mine is 100x50 squares and have incuded fstream.h
2) we set the counter of repetitions to -1 because this code offsets it easy fix actually but i was just tring to get it to work at the time.
3) we loop for a while counting how many times we see the same number in a row. then we save the count and what tile it was to the file and start on the new one.
4) we keep doing that till we are done.

Ive obtained a 40% encryption on my map which is suitable atm. if you use alot of different tiles in your maps you may not want to use this because if the number of different tiles > 50% of your map size you will be lucky to break even. But for maps with water and somewhat open areas this compression can save alot of file space. In very extreme cases you can have nearly 99.9% compression to -100% compression (tile changes every time)

Hope this helps someone. Also note 999999 is just my way of saying "end" change to your liking

It's far easier to simply write your map to a file, and compress the file then it is to come up with a map compression and store it to a file. My suggestion is you simply write your map to a text file, and use Hauffman (spelling?) Compression (in binary) to shorten the file length. If you have a need to "encrypt" the map so some one can't come along with the simple knowledge of the compression algorythm and decode the map, then do something like:
Write the map to a buffer,
Alter the binary by use of a math expression
Use the HCompression algorythem on it
Write the buffer to a file.

When reading it, just perform all that in reverse (inverse math expression)

I would rather write code and see it work than use something that is already well known. Thats what makes programming fun to me at leat write something and see it go.

EDIT: isn't this board for learning how to do stuff and not all just ask n learn?

> ifstream asd;
Don't you mean an ofstream if you're outputting?

Just now noticed i didn't toss the decrompression in here lol here it is:

Code:

void Load()
{
	int cnt=0,data=0,x=0,y=0;
	ifstream qwerty;
	qwerty.open("game.dat");
	do
	{
		qwerty>>cnt;
		qwerty>>data;
		if(cnt == 999999)break;
		
		for(cnt;cnt > 0;cnt--)
		{
			mymap[x][y] = data;			
			if(x == BMPX-1)
			{
				x = -1;
				y++;
			}
			x++;
		}
	}while(data != 999999);
	qwerty.close();
}

BMPX is a global int for max size across

actually my map is around 100000 rooms so i can either deal with 100000 ints or alot less. Image compression isnt as hard as it sounds just use jpegs instead of bitmaps

Use wads then they seem to have good compression ratios