Convert Image to Grayscale with array matrix RGB in android -

i'm creating code barre reader , have taken rgb picture , store in array using onpicturetaken(byte[] _data, camera _camera) , need convert binary matrix (greyscale) have done far

public class cam extends activity implements callback { camera camera = null; @suppresswarnings("deprecation") @override public void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     requestwindowfeature(window.feature_no_title);     surfaceview view = new surfaceview(this);     view.getholder().addcallback(this);     view.getholder().settype(surfaceholder.surface_type_push_buffers);     setcontentview(view); }     @override public void surfacechanged(surfaceholder holder, int format, int width,         int height) {     camera.parameters parameters = camera.getparameters();     parameters.setpreviewsize(width, height);     parameters.getsupportedpictureformats();      list<integer> formats = parameters.getsupportedpictureformats();         if (formats.contains(pixelformat.rgb_888))             parameters.setpictureformat(pixelformat.rgb_888);     camera.setparameters(parameters);     camera.startpreview();    }  @override public void surfacecreated(surfaceholder holder) {     try {         camera = camera.open();         camera.setpreviewdisplay(holder);     } catch (exception e) {         e.printstacktrace();     }        }  @override public void surfacedestroyed(surfaceholder holder) {     camera.stoppreview();     camera.release();     camera = null; }  @suppresslint("showtoast") @override public boolean ontouchevent(motionevent event) {     switch(event.getaction()){     case motionevent.action_down:          picturecallback jpegcallback = new picturecallback() {             public void onpicturetaken(byte[] _data, camera _camera) {                                   try {                     file fs = new file(cam.this.getfilesdir()+"/image.jpeg");                                                                    fileoutputstream fos = new fileoutputstream(fs);                     fos.write(_data);                     fos.flush();                     fos.close();                     toast.maketext(cam.this,fs.getabsolutepath(),0).show();                 } catch (exception e) {                     e.printstacktrace();                 }                 camera.startpreview();              }         };         camera.takepicture(null, null, jpegcallback);                    break;     }     return super.ontouchevent(event); } 

}

make bitmap out of , do

private byte[] converttogray(bitmap bmp) {     int width = bmp.getwidth();     int height = bmp.getheight();     byte[] grayscale = new byte[width*height];     int val, r, g, b;     (int = 0; < height; i++) {         (int j = 0; j < width; j++) {             val = bmp.getpixel(j, i);             r = (val >> 16) & 0xff ;                  g = (val >> 8) & 0xff ;              b = val & 0xff ;             grayscale[i*width + j] = (byte)(0.21*r + 0.71*g + 0.07*b);         }     }      return grayscale; 

cheers!