invdct.java

用java写的jt-jpeg。jt表示java time package

package jpeg;
import java.lang.*;
import java.util.*;
import jcp.*;

/**
 *  InvDCT.java
 *  A component that computes the inverse DCT of a block
 *
 *  Input(s):
 *      in - Takes an 8x8 matrix of integers as input.
 *  Ouput(s):
 *      out - Outputs an 8x8 matrix of the inverse DCT of the input.
 *
 *  @see IntMatrix
 */

public class InvDCT extends SynchComponent
{
    // Block size
    private final static int N = 8;

    // InvDCT coefficients
    private double[][] c;

    private Port in_p, out_p;

    public InvDCT() {
        setName("InvDCT");
        in_p = addPort(true,"in");
        out_p = addPort(false,"out");

        c = new double[N][N];
        initMatrix();
        //new inst.InstMathOps (this);
    }

    public void go(Port port) {
        Object s = port.signal();
        if (s instanceof IntMatrix) {
            int[][] matrix = ((IntMatrix)s).get_matrix();
            emit(new IntMatrix(inverseDCT(matrix)),out_p);
        }
    }

    int output[][] = new int[N][N];
    double temp[][] = new double[N][N];
    double temp1;

    public int[][] inverseDCT(int input[][])
    {
        for (int i=0; i<N; i++) {
            for (int j=0; j<N; j++) {
                temp[i][j] = 0.0;

                for (int k=0; k<N; k++) {
                    temp[i][j] += input[i][k] * c[k][j];
                }
            }
        }

        for (int i=0; i<N; i++) {
            for (int j=0; j<N; j++) {
                temp1 = 0.0;

                for (int k=0; k<N; k++) {
                    temp1 += c[k][i] * temp[k][j];
                }

                temp1 += 128.0;

                if (temp1 < 0) {
                    output[i][j] = 0;
                } else if (temp1 > 255) {
                    output[i][j] = 255;
                } else {
                     output[i][j] = (int)Math.round(temp1);
                }
            }
        }

        return output;
    }

    private void initMatrix()
    {
        for (int i = 0; i < N; i++) {
            double nn = (double)(N);
            c[0][i]  = 1.0 / Math.sqrt(nn);
        }

        for (int i = 1; i < N; i++) {
            for (int j = 0; j < N; j++) {
                double jj = (double)j;
                double ii = (double)i;
                c[i][j]  = Math.sqrt(2.0/8.0) * Math.cos(((2.0 * jj + 1.0) * ii * Math.PI) / (2.0 * 8.0));
            }
        }
    }
}