This is the original image:

and this is the thumbnail i created with gd lib 2.0.28 or somting
imagecopyresized($thumb,$src_img,0,0,0,0,$th_w,$th_h,$w,$h);
imagejpeg($thumb,"$dirnamethumbs$new_thumb_filename");

why is this thumbnail so ugly?
and the most important question is, WHAT CAN I DO TO IMPROVE QUALITY of gd lib generated thumbs???
thanks a lot