android - png downloaded size different to server size? -

my app downloads .png files sd card later use. kept getting outofmemoryerrors (if explain too, that'd great!) , took @ sizes of images saved sd card, , seem double on server. why this, , how can make them smaller?

public void oncreate(bundle saved) {      setcontentview(r.layout.namedrxnscreen);     textview t1 = (textview)findviewbyid(r.id.rxn_text1);     textview t2 = (textview)findviewbyid(r.id.rxn_text2);     textview t3 = (textview)findviewbyid(r.id.rxn_text3);     textview t4 = (textview)findviewbyid(r.id.rxn_text4);     iv = (imageview) findviewbyid(r.id.rxn_image);     pb = (progressbar) findviewbyid(r.id.rxn_loading);     vs = (viewswitcher) findviewbyid(r.id.rxn_switch);      try {          super.oncreate(saved);         [ boring stuff here ]          bitmapdrawable image = getimage(c.getstring(5));         if (image != null) {             iv.setimagedrawable(getimage(c.getstring(5)));             iv.setbackgroundcolor(color.white);             vs.setdisplayedchild(1);         }         else {             new downloadtask().execute(c.getstring(5));         }      }     catch (arrayindexoutofboundsexception ea) {         error = "bah!";         showdialog(1);     }     catch (exception ex) {         error = ex.getmessage();         showdialog(1);     } }  protected class downloadtask extends asynctask<string, integer, bitmap> {      @override     protected bitmap doinbackground(string... string) {          bitmap d = null;          try {              defaulthttpclient dhc = new defaulthttpclient();             httpget request = new httpget(http_base + string[0] + ".png");             httpresponse response = dhc.execute(request);             bufferedinputstream webstream = new bufferedinputstream(response.getentity().getcontent());             d = writetosd(string[0], webstream, d);          }         catch (exception ex) { errorcatch(ex.getmessage()); }          return d;      }      private bitmap writetosd(string string, bufferedinputstream webstream, bitmap d) {          try {              webstream.mark(3);             webstream.reset();             file f = new file(environment.getexternalstoragedirectory() + sd_dir);             f.mkdirs();             file f2 = new file(f, string + ".png");             f2.createnewfile();             bufferedoutputstream fos = new bufferedoutputstream(new fileoutputstream(f2));              int len;             byte[] buffer = new byte[1024];             while ((len = webstream.read(buffer)) > 0) {                  fos.write(buffer, 0, len);              }              webstream.close();             //fos.flush();             fos.close();              fileinputstream fis = new fileinputstream(new file(f, string + ".png"));             d = bitmapfactory.decodestream(fis);             return d;          }         catch (exception ex) {              errorcatch(ex.getmessage());             return null;          }       }      protected void onpostexecute(bitmap result) {          if (result != null) {             iv.setimagebitmap(result);             iv.setbackgroundcolor(color.white);             vs.setdisplayedchild(1);         }      }  }  protected bitmapdrawable getimage(string name) {      if (environment.getexternalstoragestate().equals(environment.media_mounted)) {          try {              //gets sd card file, whacks in stream             file f = new file(environment.getexternalstoragedirectory() + sd_dir, name + ".png");              if (f.exists()) {                  inputstream s = new fileinputstream(f);                  try {                      //return decoded bitmap                     bitmapdrawable d = new bitmapdrawable(getresources(),                              bitmapfactory.decodestream(s)); //gives outofmemoryerror if png > ~30kb                     return d;                  } catch (outofmemoryerror ex) {                      toast.maketext(this, "an outofmemoryerror occured and" +                             " image loaded @ lower quality.", toast.length_short).show();                     bitmapfactory.options moptions = new bitmapfactory.options();                     moptions.insamplesize = 4;                     bitmapdrawable d = new bitmapdrawable(getresources(),                              bitmapfactory.decodestream(s, null, moptions));                     return d;                  }              }             else return null;          }         catch (exception ex) {             return null;          }      }     else {         toast.maketext(this, "external storage not available. downloading internet.",                 toast.length_short).show();         return null;     }  } 

the picture downloaded server done byte per byte , cannot double sized magically...