Rotating a simple bitmap matrix

[TBMan]

So, I've been thinking about how to rotate a bitmap the in between degrees. (Doing 90, 180, 270 is pretty simple ). My example does produce skipped pixels in the placement of the bitmap pixels due to the rounding of the real numbers used. This works though. If you have a tile you want to rotate 45 degrees, 30 degrees, this works fairly well. What I'm doing is copying the bitmap colors from the 32x32 tile to a 32x32 rotation matrix that has a tsinglepoint type for each location in the matrix, as well as the color of the tile. The tank is one I made for a simple tank battle/capture cities game I recently started on.

Code: Pascal  [Select][+][-]

1. program rotatetank;
2. {
3.  Rotates a 32x32 tile
4. }
5.  
6.  
7. uses
8.   ptccrt,
9.   ptcgraph,
10.   Math;
11.  
12. const
13.   MAXCOL = 31;
14.  
15.   blueNorth: array [0..MAXCOL, 0..MAXCOL] of byte =
16.     ((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
17.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
18.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 41, 41, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
19.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 26, 26, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
20.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 26, 26, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
21.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 26, 26, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
22.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 26, 26, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
23.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 20, 20, 20, 26, 26, 20, 20, 20, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
24.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 20, 190, 190, 190, 26, 26, 190, 190, 190, 20, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
25.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 190, 190, 190, 26, 26, 190, 190, 190, 190, 190,20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
26.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 190, 190, 190, 26, 26, 190, 190, 190, 190, 190,20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
27.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 190, 190, 190, 26, 26, 190, 190, 190, 190, 190,20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
28.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 190, 190, 21, 26, 26, 21, 190, 190, 190, 190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
29.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 190, 21, 23, 23, 23, 23, 21, 190, 190, 190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
30.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 21, 23, 23, 23, 23, 23, 23, 21, 190, 190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
31.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 21, 23, 1, 1, 1, 1, 23, 21, 190, 190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
32.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 21, 23, 1, 1, 1, 1, 23, 21, 190, 190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
33.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 21, 23, 1, 1, 1, 1, 23, 21, 190, 190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
34.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 21, 23, 1, 1, 1, 1, 23, 21, 190, 190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
35.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 21, 23, 23, 23, 23, 23, 23, 21, 190, 190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
36.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 190, 21, 21, 21, 21, 21, 21, 190, 190, 190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
37.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190,190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
38.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190,190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
39.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190,190, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0),
40.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
41.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
42.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
43.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
44.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
45.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
46.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
47.     (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
48.  
49.  
50. type
51.  
52.   TSinglePoint = record
53.     x, y: single;
54.   end;
55.  
56.   linedata = record
57.     P: Tsinglepoint;
58.     color: byte;
59.   end;
60.  
61. var
62.   x, y: integer;
63.   r, c: integer;
64.   b: array[0..MAXCOL, 0..MAXCOL] of linedata;
65.   gmode, gdriver: smallint;
66.  
67.  
68.   procedure rotatepoint(var P: Tsinglepoint; degrees, centerx, centerY: float);
69.   var
70.     rr: integer;
71.     w, d, newx, newy, angle: float;
72.     cx, cy, y, x: single;
73.   begin
74.     angle := degTorad(degrees);
75.     cx := centerx;
76.     cy := centery;
77.     x := p.x;
78.     y := p.y;
79.     x := x - cx;
80.     Y := y - cy;
81.     newx := (x * cos(angle)) - (y * sin(angle));
82.     newy := (x * sin(angle)) + (y * cos(angle));
83.     newx := newx + cx;
84.     newy := newy + cy;
85.     p.x := newx;
86.     p.y := newy;
87.   end;
88.  
89.  
90.  
91. begin
92.   clrscr;
93.   gdriver := vesa;
94.   Gmode := installusermode(640,480, 256, 1, 8000, 6000);
95.   WindowTitle := 'Rotation';
96.   initgraph(gdriver, gmode, '');
97. // display the original while assigning x,y locations
98.   y := 200;
99.   for r := 0 to MAXCOL do
100.   begin
101.     x := 200;
102.     for c := 0 to MAXCOL do
103.     begin
104.       b[r, c].color := bluenorth[r, c];
105.       b[r, c].p.x := x + c;
106.       b[r, c].p.y := y + r;
107.       putpixel(round(b[r, c].p.x), round(b[r, c].p.y), b[r, c].color);
108.     end;
109.   end;
110.  
111. // rotate and display in new location
112.   for r := 0 to MAXCOL do
113.   begin
114.     for c := 0 to MAXCOL do
115.     begin
116. // rotate 80 degrees
117.       rotatepoint(b[r, c].p, 80, 200, 200);
118.       putpixel(round(b[r, c].p.x) + 100, round(b[r, c].p.y), b[r, c].color);
119.     end;
120.   end;
121.  
122.   readkey;
123.  
124.   closegraph;
125. end.                  
126.  
127.  
128.  

[marcov]

(Doing 90 or 270 in speedy way is also a bit more complicated).  180 is not a rotation but just flipping a boolean that changes the way of traversing the pixel data from bottomup to topdown.