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lvlslice.c

Go to the documentation of this file.

#include        "sadie.h"

/*-Copyright Information------------------------------------------------------*/
/* Copyright (c) 1988 by the University of Arizona Digital Image Analysis Lab */
/*----------------------------------------------------------------------------*/
/*-General Information--------------------------------------------------------*/
/*                                                                            */
/*   This function performs a level-slice classification on an image.         */
/*   Pixels lying within two or more boxes in feature space are assigned      */
/*   by the nearest-mean algorithm.                                           */
/*                                                                            */
/*----------------------------------------------------------------------------*/
/*-Interface Information------------------------------------------------------*/
void LVLSLICE (
IMAGE *in,      /*  I   Pointer to the input image.                           */
PIXEL *grng,    /*  I   Matrix[nlev][nbnd][2], containing class boundaries.   */
short nlev,     /*  I   Number of classes                                     */
                /*      (and number of graylevels in the output image).       */
IMAGE **out     /*  O   Address of a pointer to the output image.             */
                /*      The input image may be overwritten (out = &in).       */
/*----------------------------------------------------------------------------*/
) { register short i, j, k, l, index, count, assign, class;
    char  msg[SLEN];
    PIXEL *center=0, dnew, dold;

    if (TIMES) TIMING(T_LVLSLICE);
    if (NAMES) {
        MESSAGE('I',"");
        MESSAGE('I',"LVLSLICE");
        MESSAGE('I',"");
        sprintf(msg," Input image:         %s",in->text);
        MESSAGE('I',msg);
        sprintf(msg," Number of classes:   %d",nlev);
        MESSAGE('I',msg);
        sprintf(msg,"       ");
        for (i=0; i<in->nbnd; i++) {
            sprintf(msg+strlen(msg),"          Band %-11d",i+1);
        }
        MESSAGE('I',msg);
        sprintf(msg," Class");
        for (i=0; i<in->nbnd; i++) {
            sprintf(msg+strlen(msg),"      Min         Max     ");
        }
        MESSAGE('I',msg);
        for (i=0; i<nlev; i++) {
            sprintf(msg," %3d ",i+1);
            for (j=0; j<in->nbnd; j++) {
                sprintf(msg+strlen(msg),"%14.4e%12.4e",grng[(i*in->nbnd+j)*2+0],grng[(i*in->nbnd+j)*2+1]);
            }
            MESSAGE('I',msg);
        }
        MESSAGE('I'," ...............");
    }

    /* check input */
    if (!CHECKIMG(in)) {
        MESSAGE('E'," Can't identify image.");
        goto the_end;
    } else if (nlev <= 0) {
        MESSAGE('E'," Number of classes must be greater than zero.");
        goto the_end;
    }

    /* create image of appropriate size */
    if (!CHECKIMG(*out)) GETMEM(1,in->nlin,in->npix,out);
    if (!*out) goto the_end;

    /* allocate space for center array */
    if (!(center=(PIXEL *)malloc(nlev*in->nbnd*sizeof(PIXEL)))) {
        MESSAGE('E'," Memory request failed.");
        goto the_end;
    }

    /* compute center coordinates for each class  */
    for (j=i=0; i<nlev*in->nbnd; i++) {
        center[i] = (grng[j++]+grng[j++])/2.0;
    }

    /* perform a level slice classification */
    for (j=0; j<in->nlin; j++) {
        for (k=0; k<in->npix; k++) {
            for (assign=index=class=l=0; l<nlev; l++) {
                for (index=l*in->nbnd*2,count=i=0; i<in->nbnd; i++) {
                    if (grng[index++] <= in->data[i][j][k]  &&  in->data[i][j][k] <= grng[index++]) {
                        count += 1;
                    } else {
                        break;
                    }
                }
                if (count == in->nbnd) {
                    if (assign == 0) {
                        class  = l + 1;
                        assign = 1;
                    } else /* calculate distance to competing classes */ {
                        for (dold=dnew=0.0,i=0; i<in->nbnd; i++) {
                            dold += (in->data[i][j][k]-center[(class-1)*in->nbnd+i])*(in->data[i][j][k]-center[(class-1)*in->nbnd+i]);
                            dnew += (in->data[i][j][k]-center[l*in->nbnd+i])*(in->data[i][j][k]-center[l*in->nbnd+i]);
                        }
                        if (dnew < dold) class = l + 1;
                    }
                }
            }
            (*out)->data[0][j][k] = (PIXEL)class;
        }
    }

    the_end:
    if (center) free(center);
    if (TIMES)  TIMING(T_EXIT);
}

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