DWT Example Code

DWT/IDWT Example

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "../header/wavelib.h"

double absmax(double *array, int N) {
        double max;
        int i;

        max = 0.0;
        for (i = 0; i < N; ++i) {
                if (fabs(array[i]) >= max) {
                        max = fabs(array[i]);
                }
        }

        return max;
}

int main() {
        wave_object obj;
        wt_object wt;
        double *inp,*out,*diff;
        int N, i,J;

        FILE *ifp;
        double temp[1200];

        char *name = "db4";
        obj = wave_init(name);// Initialize the wavelet

        ifp = fopen("signal.txt", "r");
        i = 0;
        if (!ifp) {
                printf("Cannot Open File");
                exit(100);
        }
        while (!feof(ifp)) {
                fscanf(ifp, "%lf \n", &temp[i]);
                i++;
        }
        N = 256;

        inp = (double*)malloc(sizeof(double)* N);
        out = (double*)malloc(sizeof(double)* N);
        diff = (double*)malloc(sizeof(double)* N);
        //wmean = mean(temp, N);

        for (i = 0; i < N; ++i) {
                inp[i] = temp[i];
                //printf("%g \n",inp[i]);
        }
        J = 3;

        wt = wt_init(obj, "dwt", N, J);// Initialize the wavelet transform object
        setDWTExtension(wt, "sym");// Options are "per" and "sym". Symmetric is the default option
        setWTConv(wt, "direct");
       
        dwt(wt, inp);// Perform DWT
        //DWT output can be accessed using wt->output vector. Use wt_summary to find out how to extract appx and detail coefficients
       
        for (i = 0; i < wt->outlength; ++i) {
                printf("%g ",wt->output[i]);
        }
       
        idwt(wt, out);// Perform IDWT (if needed)
        // Test Reconstruction
        for (i = 0; i < wt->siglength; ++i) {
                diff[i] = out[i] - inp[i];
        }
       
        printf("\n MAX %g \n", absmax(diff, wt->siglength)); // If Reconstruction succeeded then the output should be a small value.
       
        wt_summary(wt);// Prints the full summary.
        wave_free(obj);
        wt_free(wt);

        free(inp);
        free(out);
        free(diff);
        return 0;
}