ios - Mask out specific pixels from a UIView based on where subviews are located -

say have main uiview has several subviews of type catview , dogview. want render uiview image, want exclude dogviews, final rendered image has transparent pixels in place of dogview. (note removing dogviews view wouldn't work - need transparent pixels dogviews were). dogviews can rotated don't take rectangular portions of view.

any ideas on how can approach this?

edit: first attempt

- (uiimage *)createcutoutviewfromview:(uiview*)view {      uigraphicsbeginimagecontextwithoptions(view.bounds.size, no, 0.0);     cgcontextref context = uigraphicsgetcurrentcontext();      cgcontextmovetopoint(context, 200, 200);     cgcontextaddlinetopoint(context, 250, 200);     cgcontextaddlinetopoint(context, 250, 250);     cgcontextaddlinetopoint(context, 200, 250);     cgcontextclosepath(context);      cgcontextclip(context);      [view.layer renderincontext:context];      uiimage *result = uigraphicsgetimagefromcurrentimagecontext();     uigraphicsendimagecontext();      return result;  } 

the result can see 50px rectangle clipped. want see except rectangle. advice?

edit: 2nd attempt

- (uiimage *)createcutoutviewfromview:(uiview*)view {      uigraphicsbeginimagecontextwithoptions(view.bounds.size, no, 0.0);     cgcontextref context = uigraphicsgetcurrentcontext();     cgcontextclearrect(context, view.bounds);      [view.layer renderincontext:context];      uibezierpath* path = [uibezierpath bezierpath];     [path movetopoint:cgpointmake(200, 200)];     [path addlinetopoint:cgpointmake(250, 200)];     [path addlinetopoint:cgpointmake(250, 250)];     [path addlinetopoint:cgpointmake(200, 250)];     [path closepath];      [path fillwithblendmode:kcgblendmodenormal alpha:0.0];       uiimage *result = uigraphicsgetimagefromcurrentimagecontext();     uigraphicsendimagecontext();       return result;  } 

create bitmapped graphics context , render view context. each dogview, create uibezierpath, , use movetopoint, addlinetopoint, , closepath draw outline dogview be. call fillwithblendmode:alpha: alpha of 0.0 clear region of drawing.

i use uigraphicsbeginimagecontext create bitmapped graphics context since needs size, can view's bounds. here's general framework.

uigraphicsbeginimagecontext( view.bounds.size ); cgcontextref context = uigraphicsgetcurrentcontext();  // drawing stuff goes here  uiimage *result = uigraphicsgetimagefromcurrentimagecontext(); uigraphicsendimagecontext();