ios - How to mix two colors at the point of intersection of paths in Coregraphics? -


i need mix 2 colors on drawing smooth curves in image view, in - mixing of red , blue should give purple (red+yellow = orange,yellow+blue=green) @ point of intersection of 2 colors. tried using blending modes of coregraphics did not work. can me out?

-(void)touchesmoved:(nsset<uitouch *> *)touches withevent:(uievent *)event {     uitouch *touch = [touches anyobject];     self.prepreviouspoint = self.previouspoint;     self.previouspoint = [touch previouslocationinview:self];     cgpoint currentpoint = [touch locationinview:self];     cgpoint mid1 = [self calculatemidpointforpoint:self.previouspoint andpoint:self.prepreviouspoint];     cgpoint mid2 = [self calculatemidpointforpoint:currentpoint andpoint:self.previouspoint];      uigraphicsbeginimagecontext(self.drawimageview.frame.size);     cgcontextref context = uigraphicsgetcurrentcontext();     [currentcolor setstroke];     cgcontextsetblendmode(context, kcgblendmodemultiply);      cgcontextsetallowsantialiasing(uigraphicsgetcurrentcontext(), true);     cgcontextsetshouldantialias(uigraphicsgetcurrentcontext(), true);     [self.drawimageview.image drawinrect:cgrectmake(0, 0, self.drawimageview.frame.size.width, self.drawimageview.frame.size.height)];      cgcontextmovetopoint(context, mid1.x, mid1.y);     //    // use quadcurve key     cgcontextaddquadcurvetopoint(context, self.previouspoint.x, self.previouspoint.y, mid2.x, mid2.y);      cgcontextsetlinecap(context, kcglinecapround);      cgcontextsetlinewidth(context, self.linewidth);      cgcontextstrokepath(context);       self.drawimageview.image = uigraphicsgetimagefromcurrentimagecontext();      uigraphicsendimagecontext(); }


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