rounded corners uiimage

i'm perplexing pull images iphone controlling lifeless corners, la hit images contacts app. i've got formula generally work, nonetheless catchy crashes inside uiimage sketch routines an exec_bad_access - kern_invalid_address. i guess competence associated i asked few weeks back, nonetheless i trust i'm sourroundings adult writing route correctly.

here's formula i'm controlling - doesn't crash, outcome looks glorious anybody looking identical feeling giveaway steal code.

- (uiimage *)borderedimagewithrect: (cgrect)dstrect radius:(cgfloat)radius {
    uiimage *maskedimage = nil;

    radius = min(radius, .5 * min(cgrectgetwidth(dstrect), cgrectgetheight(dstrect)));
    cgrect interiorrect = cgrectinset(dstrect, radius, radius);

    uigraphicsbeginimagecontext(dstrect.size);
    cgcontextref maskedcontextref = uigraphicsgetcurrentcontext();
    cgcontextsavegstate(maskedcontextref);

    cgmutablepathref borderpath = cgpathcreatemutable();
    cgpathaddarc(borderpath, null, cgrectgetminx(interiorrect), cgrectgetminy(interiorrect), radius, pndegreetoradian(180), pndegreetoradian(270), no);
    cgpathaddarc(borderpath, null, cgrectgetmaxx(interiorrect), cgrectgetminy(interiorrect), radius, pndegreetoradian(270.0), pndegreetoradian(360.0), no);
    cgpathaddarc(borderpath, null, cgrectgetmaxx(interiorrect), cgrectgetmaxy(interiorrect), radius, pndegreetoradian(0.0), pndegreetoradian(90.0), no);
    cgpathaddarc(borderpath, null, cgrectgetminx(interiorrect), cgrectgetmaxy(interiorrect), radius, pndegreetoradian(90.0), pndegreetoradian(180.0), no);

    cgcontextbeginpath(maskedcontextref);
    cgcontextaddpath(maskedcontextref, borderpath);
    cgcontextclosepath(maskedcontextref);
    cgcontextclip(maskedcontextref);

    [self drawinrect: dstrect];

    maskedimage = uigraphicsgetimagefromcurrentimagecontext();
    cgcontextrestoregstate(maskedcontextref);
    uigraphicsendimagecontext();

    relapse maskedimage;
}

and here's wreck log. looks same whenever i crashes

exception type:  exc_bad_access (sigsegv)
exception codes: kern_invalid_address during 0x6e2e6181
crashed thread:  0

thread 0 crashed:
0   com.apple.coregraphics          0x30fe56d8 cggstategetrenderingintent + 4
1   librip.a.dylib                  0x33c4a7d8 ripc_renderimage + 104
2   librip.a.dylib                  0x33c51868 ripc_drawimage + 3860
3   com.apple.coregraphics          0x30fecad4 cgcontextdelegatedrawimage + 80
4   com.apple.coregraphics          0x30feca40 cgcontextdrawimage + 368
5   uikit                           0x30a6a708 -[uiimage drawinrect:blendmode:alpha:] + 1460
6   uikit                           0x30a66904 -[uiimage drawinrect:] + 72
7   myapp                           0x0003f8a8 -[uiimage(pnadditions) borderedimagewithrect:radius:] (uiimage+pnadditions.m:187)