DCT算法java 实现 。此版本的效率比较低

DCT2.java

public class DCT2 {
	  private static final int N = 130;
	    private double[] c = new double[N];

	    public DCT2() {
	          this.initializeCoefficients();
	    }

	    private void initializeCoefficients() {
	        for (int i=1;i<N;i++) {
	            c[i]=1;
	        }
	        c[0]=1/Math.sqrt(2.0);
	    }

	    public double[][] applyDCT(double[][] f) {
	        double[][] F = new double[N][N];
	        for (int u=0;u<N;u++) {
	          for (int v=0;v<N;v++) {
	            double sum = 0.0;
	            for (int i=0;i<N;i++) {
	              for (int j=0;j<N;j++) {
	                sum+=Math.cos(((2*i+1)/(2.0*N))*u*Math.PI)*Math.cos(((2*j+1)/(2.0*N))*v*Math.PI)*f[i][j];
	              }
	            }
	            sum*=(2 * c[u]*c[v])/Math.sqrt(N*N);
	            F[u][v]=sum;
	          }
	        }
	        return F;
	    }
	    
	    public double[][] applyDCT(int[][] f){
	    	double[][]	 fd = new double[f.length][f[0].length];
	    	for (int i = 0; i < f.length; i++) {
				for (int j = 0; j < f[0].length; j++) {
					fd[i][j] = f[i][j];
				}
			}
	    	return applyDCT(fd);
	    }

	    public double[][] applyIDCT(double[][] F) {
	        double[][] f = new double[N][N];
	        for (int i=0;i<N;i++) {
	          for (int j=0;j<N;j++) {
	            double sum = 0.0;
	            for (int u=0;u<N;u++) {
	              for (int v=0;v<N;v++) {
	                sum += (2 * c[u]*c[v])/Math.sqrt(N*N)*Math.cos(((2*i+1)/(2.0*N))*u*Math.PI)*Math.cos(((2*j+1)/(2.0*N))*v*Math.PI)*F[u][v];
	              }
	            }
	            f[i][j]=Math.round(sum);
	          }
	        }
	        return f;
	    }
	    

	    
		public String getFingerString(double[][] f,int dimension){
			StringBuilder hash = new StringBuilder();
		      /* 
		       * 计算DCT的平均值 
		       */
		      double total = 0;
		      
		      for (int x = 0; x < dimension; x++) {
		          for (int y = 0; y < dimension; y++) {
		              total += f[x][y];
		          }
		      }
		      
		      double avg = total / (double) ((dimension * dimension));
		      for (int x = 0; x < dimension; x++) {
		          for (int y = 0; y < dimension; y++) {	              
		        	  hash.append(f[x][y] > avg? "1" : "0");
		          }
		      }
			return hash.toString();		
		}
}