HV* countColors( SV *img ) {
    STRLEN l;
    U32 *rgba = (U32*)SvPVx( img, l ), i;
    HV* counts = newHV();
    SV *dummy = newSV( 4 );

    l /= 4;
    for( i = 0; i < l; ++i ) {
        U32 hash;
        PERL_HASH( (U32)hash, (char*)&rgba[ i ], 4 );
        SvPV_set( dummy, (char*)&rgba[ i ] );

        if( hv_exists_ent( counts, dummy, hash  ) ) {
            SV **val = hv_fetch( counts, (char*)&rgba[ i ], 4, hash );
            SvIV_set( *val, SvIV( *val ) + 1 );
        }
        else {
            SV *val = newSViv( 1 );
            hv_store( counts, (char*)&rgba[ i ], 4, val, hash );
        }
    }
    return counts;
}