Definitely the first one.
Also, BuilderBoy wrote a good tutorial on RLE, here it is:
Map data format:
The data uses run length encoding for comression. Lets say we had a simple map:
11111000001111
00000222220000
Pretty simple, each number representing a different tile. With normal storage this would take
a single byte per tile. Or we could represent the data in a different way:
150514052504
Seems much smaller, but what does it mean? lets insert some imaginary commas and dashes to make
it easier:
1-5,0-5,1-4,0-5,2-5,0-4
Now you may or may not be able to see how the data is represented. The first segment is 1-5, or 5 '1's in
a row, followed by 0-5, or five '0's in a row, and so on. This is how the data in run length encoding is
represented. And to further the compression (or confusion), each #-# segment is packed into a single byte.
Instead of two hex digits to represent a number from 0-255, we will have 2 hex digits, each from 0-15,
representing the two numbers of each #-# element.
The first Hex digit 0 to 15 is the tile number. The second hex digit is the number of tiles to add to the
tilemap. The digit goes from 0-15, but 0 doesnt make much sense, since that would mean this element doesnt
do anything
, so we will add one to this after we decompress it so that it has a range of 1 to 16.
There is a small disadvantage that if you have empty spaces of 17 or more in a row, it will take more than
1 byte to represent in the code.
[Data]->GDB1 //map data to GDB1
[tileData]->Pic1 //tile data for tilemap
0->N //element index for map data
0->I //map index for storing tile data
While I>=96 //until we have stored all tiles
{GBD+N}->A //Take the first element of the map data
N+1->N //Increment the map index
A^16->B //spit the map element into it
A/16->A two seperate elements
For(F,0,B //fill the map from current position I to I+B
A->{L1+I} //could be optimised with Fill but i couldnt get it
I+1->I //working
End
End //End while
After this code is run, the tile data will be decompressed into L1, as folows
0 1 2 3 4 5 6
7 8 9 10 11 12 13...
ect, it will be in a straigt line, but you will have to access it using your own routine. Something like this
{Y*W+X+L1}
where W is the width in tiles of your map. X and Y would be the tile coordinates starting at the top left at
0,0.
Displaying the map:
here is a rudimentary program that should be run right after the pervious decompressing program:
For(X,0,11 //loop through the entire screen coordinates with tiles of 8x8
For(Y,0,7
{Y*12+X+L1}->A //retrieve the correct tile from the data in L1
Pt-On(X*8,Y*8,A*8+Pic1 //draw the sprite to the screen
End
End
...hope he doesn't mind my posting it here.
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