Function pam_computeacolorhash

mapquantization.c:614–658

( apixels, cols, rows, maxacolors, acolorsP )

static acolorhash_table
pam_computeacolorhash( apixels, cols, rows, maxacolors, acolorsP )
rgbaPixel** apixels;
int cols, rows, maxacolors;
int* acolorsP;
{
    acolorhash_table acht;
    register rgbaPixel* pP;
    acolorhist_list achl;
    int col, row, hash;

    acht = pam_allocacolorhash( );
    *acolorsP = 0;

    /* Go through the entire image, building a hash table of colors. */
    for ( row = 0; row < rows; ++row )
        for ( col = 0, pP = apixels[row]; col < cols; ++col, ++pP )
        {
            hash = pam_hashapixel( *pP );
            for ( achl = acht[hash]; achl != (acolorhist_list) 0; achl = achl->next )
                if ( PAM_EQUAL( achl->ch.acolor, *pP ) )
                    break;
            if ( achl != (acolorhist_list) 0 )
                ++(achl->ch.value);
            else
            {
                if ( ++(*acolorsP) > maxacolors )
                {
                    pam_freeacolorhash( acht );
                    return (acolorhash_table) 0;
                }
                achl = (acolorhist_list) malloc( sizeof(struct acolorhist_list_item) );
                if ( achl == 0 ) {
                    fprintf( stderr, "  out of memory computing hash table\n" );
                    exit(7);
                }
                achl->ch.acolor = *pP;
                achl->ch.value = 1;
                achl->next = acht[hash];
                acht[hash] = achl;
            }
        }

    return acht;
}