[bmx] Run Length Encoding by zoqfotpik [ 1+ years ago ]

[BlitzBot]

Title : Run Length Encoding
Author : zoqfotpik
Posted : 1+ years ago

Description : Run Length Encoding is a simple form of compression for strings or arrays that contain a lot of blocks of the same consecutive characters, like "1111111111155555555222222222" which would compress to
11,1
8,5
9,2

Obviously real game levels from eg. platformers offer much larger dividends and they're close to best-case, like thousand-to-one compression ratios. If you have lots and lots of little blocks you might be better off doing something else.

This expects your level to be 128x128 and in a 2D array called maparray.  It is just two functions with no demo code-- to test it just make a global maparray:int[128,128], write some data in there, then call writelevel and respond to the input on the text console.

The reason why I wrote this was for distribution of mobile games with hundreds of levels in a tiny and quick download.

Enjoy!

Code :

Code: BlitzMax

1. Function writelevel()
2.  
3.         Local levname$
4.        
5.         levname$ = Input ("Filename:")
6.         Local success=CreateFile(levname$)
7.         If Not success RuntimeError "error creating file"      
8.         Local file:TStream =WriteFile(levname$)
9.  
10.         Local x = 0  ' set to upper left of array
11.         Local y = 0
12.         Local currentrun = 0
13.         Local currenttile = 0
14.        
15.         Print "trying to write file..."
16.         While y < 127
17.         currenttile = maparray[x,y]
18.         x = x + 1
19.         If x > 127
20.                 y = y + 1
21.                 x = 0
22.         EndIf
23.        
24.         If maparray[x,y] = currenttile
25.                 currentrun = currentrun + 1
26.        
27.         Else  ' run is broken
28.                 Print "writing line"
29.                 WriteLine file,currentrun + 1+ "," + currenttile
30.                 currentrun = 0
31.         EndIf
32.         Wend
33.         WriteLine file,"10000,1"
34.         CloseFile file
35. End Function
36.  
37. Function readlevel()
38.                 Local levname$
39.                 Local file:TStream
40.                 Local lines:String[]
41.                 Local line:String
42.                 Local values:String[]
43.                 Local templine:String[]
44.                 Local teststringiter:String
45.                 Local x:Int
46.                 Local y:Int
47.                 Local i:Int
48.                
49.                 levname$ = Input ("Filename:")
50.                
51.                 file=ReadFile(levname)
52.  
53.                 If Not file RuntimeError "could not open file " + levname
54.                
55.                 While Not Eof(file)
56.                         templine = ReadLine(file).split("
57. ")
58.                                 templine = templine[0].split(",")
59.                                 Print templine[0]
60.                             printtilename(Int(templine[0]))
61.                                 i = 0
62.                                 Local runnumber:Int = Int(templine[0])
63.                         Local tiletype:Int = Int(templine[1])
64.                                 For i = 0 To runnumber-1
65.                                 maparray[x,y]=tiletype
66.                                     x = x + 1
67.                                     If x > 127
68.                                         x = 0
69.                                         y = y + 1
70.                                     EndIf
71.                                  Next
72.                 Wend
73.                 CloseStream file
74. End Function

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