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Java > Open Source Codes > JSci > maths > wavelet > daubechies2 > FastDaubechies2


1 package JSci.maths.wavelet.daubechies2;
2
3 import JSci.maths.wavelet.FWT;
4
5 /************************
6 * This is a very fast implementation of the
7 * Fast Wavelet Transform. It uses in-place computations
8 * for less memory usage. Data length should be
9 * a power of 2 a be at least of length 4.
10 * Handles boundaries by assuming periodicity.
11 * Ideal for image processing or processing large
12 * amount of data. Uses floats for more performance.
13 * Safety is minimal, so be careful!
14 * @author Daniel Lemire
15 *************************/
16 public final class FastDaubechies2 extends FWT {
17   static final private float root3 = (float)(Math.sqrt(3.0));
18   static final private float normalizer = (float)(Math.pow(2d,-.5d));
19   static final float[] scale = {(1f+(root3))*normalizer/4f,(3f+(root3))*normalizer/4f,(3f+(-1*(root3)))*normalizer/4f,(1f+(-1*(root3)))*normalizer/4f};
20   static final float[] wavelet = {-(1f+(-1*(root3)))*normalizer/4f,(3f+(-1*(root3)))*normalizer/4f,-(3f+(root3))*normalizer/4f,(1f+(root3))*normalizer/4f};
21
22
23   public FastDaubechies2() {
24   }
25
26   public static void transform (float[] v,int last) {
27     float[] ans=new float[last];
28     final int half=last/2;
29     try {
30       for(int k=0;/*k<half*/;k++) {
31           ans[k+half]=v[(2*k+0)]*wavelet[0]+v[(2*k+1)]*wavelet[1]+v[(2*k+2)]*wavelet[2]+v[(2*k+3)]*wavelet[3];
32           ans[k]=v[(2*k+0)]*scale[0]+v[(2*k+1)]*scale[1]+v[(2*k+2)]*scale[2]+v[(2*k+3)]*scale[3];
33       }
34     } catch (IndexOutOfBoundsException JavaDoc e) {}
35     ans[last-1]=v[last-2]*wavelet[0]+v[last-1]*wavelet[1]+v[0]*wavelet[2]+v[1]*wavelet[3];
36     ans[half-1]=v[last-2]*scale[0]+v[last-1]*scale[1]+v[0]*scale[2]+v[1]*scale[3];
37
38     System.arraycopy(ans,0,v,0,last);
39   }
40
41   public void transform (float[] v) {
42     int last;
43     for (last=v.length;last>4;last/=2) {
44       transform(v,last);
45     }
46     if(last!=4)
47       System.err.println("Careful! this should be a power of 2 : "+v.length);
48   }
49
50   public void invTransform(float[] v) {
51     int last;
52     for (last=4;2*last<=v.length;last*=2) {
53       invTransform(v,last);
54     }
55     if(last!=v.length)
56       System.err.println("Careful! this should be a power of 2 : "+v.length);
57
58   }
59
60   public static void invTransform (float[] v, int last) {
61     int ResultingLength=2*last;
62     float[] ans=new float[ResultingLength];
63     try {
64       for(int k=0;/*k<last*/;k++) {
65           ans[(2*k+3)]+=scale[3]*v[k]+wavelet[3]*v[k+last] ;
66           ans[(2*k+2)]+=scale[2]*v[k]+wavelet[2]*v[k+last] ;
67           ans[(2*k+1)]+=scale[1]*v[k]+wavelet[1]*v[k+last] ;
68           ans[(2*k+0)]+=scale[0]*v[k]+wavelet[0]*v[k+last] ;
69       }
70     } catch (IndexOutOfBoundsException JavaDoc e) {}
71     ans[ResultingLength-2]+=scale[0]*v[last-1]+wavelet[0]*v[ResultingLength-1] ;
72     ans[ResultingLength-1]+=scale[1]*v[last-1]+wavelet[1]*v[ResultingLength-1] ;
73     ans[0]+=scale[2]*v[last-1]+wavelet[2]*v[ResultingLength-1] ;
74     ans[1]+=scale[3]*v[last-1]+wavelet[3]*v[ResultingLength-1] ;
75     System.arraycopy(ans,0,v,0,ans.length);
76   }
77 }
78
79
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