ios - Objective C - Sketch Application will not draw long lines -

i have iphone app provide sketch pad user save signature. uiimageview gets added main view , holds strokes. reason can draw short lines on pad following image.

i have application ipad uses same code , works fine. i'm not sure causing it. i'm not using touch or gesture code interfere it. following of code use.

update: if create uiviewcontroller same class , make root view controller works fine. in navigation hierarchy doing weird.

-(void)setupsignaturepad{ //create frame our signature capture imageframe = cgrectmake(self.view.frame.origin.x,                         self.view.frame.origin.y,                         self.view.frame.size.width + 23,                         self.view.frame.size.height + 7 ); //allocate image view , add main view     mysignatureimage = [[uiimageview alloc] initwithimage:nil];     mysignatureimage.frame = imageframe;     mysignatureimage.backgroundcolor = [uicolor whitecolor];     [self.view addsubview:mysignatureimage]; }  //when 1 or more fingers touch down in view or window - (void)touchesbegan:(nsset *)touches withevent:(uievent *)event {  //did our finger moved yet? fingermoved = no; uitouch *touch = [touches anyobject];  //we need 3 points of contact make our signature smooth using quadratic bezier curve currentpoint = [touch locationinview:mysignatureimage]; lastcontactpoint1 = [touch previouslocationinview:mysignatureimage]; lastcontactpoint2 = [touch previouslocationinview:mysignatureimage];   //when 1 or more fingers associated event move within view or window - (void)touchesmoved:(nsset *)touches withevent:(uievent *)event {  //well obvious our finger moved on screen fingermoved = yes; uitouch *touch = [touches anyobject];  //save previous contact locations lastcontactpoint2 = lastcontactpoint1; lastcontactpoint1 = [touch previouslocationinview:mysignatureimage]; //save current location currentpoint = [touch locationinview:mysignatureimage];  //find mid points used quadratic bezier curve cgpoint midpoint1 = [self midpoint:lastcontactpoint1 withpoint:lastcontactpoint2]; cgpoint midpoint2 = [self midpoint:currentpoint withpoint:lastcontactpoint1];  //create bitmap-based graphics context , makes current context uigraphicsbeginimagecontext(imageframe.size);  //draw entire image in specified rectangle frame [mysignatureimage.image drawinrect:cgrectmake(0, 0, imageframe.size.width, imageframe.size.height)];  //set line cap, width, stroke color , begin path cgcontextsetlinecap(uigraphicsgetcurrentcontext(), kcglinecapround); cgcontextsetlinewidth(uigraphicsgetcurrentcontext(), 3.0f); cgcontextsetrgbstrokecolor(uigraphicsgetcurrentcontext(), 0.0, 0.0, 0.0, 1.0); cgcontextbeginpath(uigraphicsgetcurrentcontext());  //begin new new subpath @ point cgcontextmovetopoint(uigraphicsgetcurrentcontext(), midpoint1.x, midpoint1.y); //create quadratic bézier curve current point using control point , end point cgcontextaddquadcurvetopoint(uigraphicsgetcurrentcontext(),                              lastcontactpoint1.x, lastcontactpoint1.y, midpoint2.x, midpoint2.y);  //set miter limit joins of connected lines in graphics context cgcontextsetmiterlimit(uigraphicsgetcurrentcontext(), 2.0);  //paint line along current path cgcontextstrokepath(uigraphicsgetcurrentcontext());  //set image based on contents of current bitmap-based graphics context mysignatureimage.image = uigraphicsgetimagefromcurrentimagecontext();  //remove current bitmap-based graphics context top of stack uigraphicsendimagecontext();  }  - (void)touchesended:(nsset *)touches withevent:(uievent *)event { //if finger never moved draw point if(!fingermoved) {     uigraphicsbeginimagecontext(imageframe.size);     [mysignatureimage.image drawinrect:cgrectmake(0, 0, imageframe.size.width, imageframe.size.height)];      cgcontextsetlinecap(uigraphicsgetcurrentcontext(), kcglinecapround);     cgcontextsetlinewidth(uigraphicsgetcurrentcontext(), 3.0f);     cgcontextsetrgbstrokecolor(uigraphicsgetcurrentcontext(), 0.0, 0.0, 0.0, 1.0);     cgcontextmovetopoint(uigraphicsgetcurrentcontext(), currentpoint.x, currentpoint.y);     cgcontextaddlinetopoint(uigraphicsgetcurrentcontext(), currentpoint.x, currentpoint.y);     cgcontextstrokepath(uigraphicsgetcurrentcontext());     cgcontextflush(uigraphicsgetcurrentcontext());      mysignatureimage.image = uigraphicsgetimagefromcurrentimagecontext();     uigraphicsendimagecontext();     } }  //calculate midpoint between 2 points - (cgpoint) midpoint:(cgpoint )p0 withpoint: (cgpoint) p1 {     return (cgpoint) {         (p0.x + p1.x) / 2.0,         (p0.y + p1.y) / 2.0     }; } 

i'm sorry tell haven't real solution, problem due performance issues. why? because creating image each time gesture detected. creating images requires of screen renderings takes time , resources.
should base code on same project has drawing functionalities, use view updates draw in drawrect method, maybe cashapelaywr fine.
run time profiler in instruments , search wich method tanking time.