iphone - CGContextAddEllipseInRect to CGImageRef to CGImageMaskCreate to CGContextClipToMask -

i haven't been able find 1 single example on internets teaches me how create circle on fly , use circle clip uiimage.

here's code, unfortunately doesn't give me desired results.

//create graphics context uigraphicsbeginimagecontext(cgsizemake(243, 243)); cgcontextref context = uigraphicsgetcurrentcontext();  //create object in context cgcontextaddellipseinrect(context, cgrectmake(0, 0, 243, 243)); cgcontextsetfillcolor(context, cgcolorgetcomponents([[uicolor whitecolor] cgcolor])); cgcontextfillpath(context);  uiimage *image = uigraphicsgetimagefromcurrentimagecontext(); //create uiimage ellipse   //get drawing image cgimageref maskimage = [image cgimage];  // mask image cgimageref maskref = cgimagemaskcreate(cgimagegetwidth(maskimage)                                     , cgimagegetheight(maskimage)                                     , cgimagegetbitspercomponent(maskimage)                                     , cgimagegetbitsperpixel(maskimage)                                     , cgimagegetbytesperrow(maskimage)                                     ,  cgimagegetdataprovider(maskimage)                                     , null                                     , false);   //finally clip context mask.  cgcontextcliptomask( context , cgrectmake(0, 0, 243, 243) , maskref );   //draw image [firstpieceview.image drawinrect:cgrectmake(0, 0, 320, 480)]; // [firstpieceview drawrect:cgrectmake(0, 0, 320, 480)];  //extract new image uiimage *outputimage = uigraphicsgetimagefromcurrentimagecontext();  nslog(@"self.firstpieceview %@", nsstringfromcgrect(self.firstpieceview.frame)); uigraphicsendimagecontext();   self.firstpieceview.image = outputimage; 

i appreciate directions.

i suspect need rephrase question better. there's plenty of example code whatever you're trying out there.

here's how implement custom uiview subclass clip image ellipse:

- (void)drawinrect:(cgrect)rect {   uiimage image;// set/get somewhere   cgimageref imageref = [image cgimageref];   cgcontextref context = uigraphicsgetcurrentcontext();   cgcontextaddellipseinrect(context, self.bounds);   cgcontextclip(context);   cgcontextdrawimage(context, self.bounds, imageref); } 

caveat emptor

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edit (a day later, free time produces):

- (void)drawrect:(cgrect)rect {   // we're ignoring rect , drawing whole view   cgimageref imageref = [_image cgimage]; // ivar: uiimage *_image;   cgcontextref context = uigraphicsgetcurrentcontext();    // set background black   [[uicolor blackcolor] setfill];   cgcontextfillrect(context, self.bounds);     // modify context coordinates,   // uikit , coregraphics oriented differently   cgcontextsavegstate(context);     cgcontexttranslatectm(context, 0, cgrectgetheight(rect));     cgcontextscalectm(context, 1, -1);      // add clipping path context, execute clip     // in effect drawing until gstate restored     cgcontextaddellipseinrect(context, self.bounds);     cgcontextclip(context);      // stretch image size of view     cgcontextdrawimage(context, self.bounds, imageref);   cgcontextrestoregstate(context); }