cocoa - Core Graphics: Drawing along a path with a normal gradient -

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there number of resources here , elsewhere on web regarding how draw gradient - fill or stroke.

however, afaict, none addresses following requirement: how draw path normal gradient, whereby normal means orthogonal path. net effect toothpaste or tube when applied dark->light->dark linear gradient. here idea in case of round rectangle:

round-rect tube http://muys.net/cadre_blanc.png

(this hand drawn , corners not good).

in specific case of round rect, think can achieve effect 4 linear gradients (the sides) , 4 radial gradients (the corners). there better?

is there easy solution path?

the "easy" solution can think of stroke path multiple times, reducing stroke width , changing color each time, simulate gradient.

obviously, expensive operation complex paths want cache result if possible.

#define rkrandom(x) (arc4random() % ((nsuinteger)(x) + 1))  @implementation strokeview  - (void)drawrect:(nsrect)rect  {     nsrect bounds = self.bounds;      //first draw using core graphics calls     cgcontextref c = [[nsgraphicscontext currentcontext] graphicsport];      cgmutablepathref path = cgpathcreatemutable();      cgpathmovetopoint(path, null, nsmidx(bounds), nsmidy(bounds));     cgcontextsetmiterlimit(c,90.0);     cgcontextsetlinejoin(c, kcglinejoinround);     cgcontextsetlinecap(c, kcglinecapround);      for(nsuinteger f = 0; f < 20; f++)     {         cgpathaddcurvetopoint(                               path,                               null,                               (cgfloat)rkrandom((nsinteger)nswidth(bounds)) + nsminx(bounds),                                (cgfloat)rkrandom((nsinteger)nsheight(bounds)) + nsminy(bounds),                               (cgfloat)rkrandom((nsinteger)nswidth(bounds)) + nsminx(bounds),                                (cgfloat)rkrandom((nsinteger)nsheight(bounds)) + nsminy(bounds),                               (cgfloat)rkrandom((nsinteger)nswidth(bounds)) + nsminx(bounds),                                (cgfloat)rkrandom((nsinteger)nsheight(bounds)) + nsminy(bounds)                               );     }      for(nsinteger = 0; < 8; i+=2)     {         cgcontextsetlinewidth(c, 8.0 - (cgfloat)i);         cgfloat tint = (cgfloat)i * 0.15;          cgcontextsetrgbstrokecolor (                                     c,                                     1.0,                                     tint,                                     tint,                                     1.0                                     );         cgcontextaddpath(c, path);         cgcontextstrokepath(c);     }      cgpathrelease(path);      //now draw using cocoa drawing     nsbezierpath* cocoapath = [nsbezierpath bezierpathwithroundedrect:nsinsetrect(self.bounds, 20.0, 20.0) xradius:10.0 yradius:10.0];     for(nsinteger = 0; < 8; i+=2)     {         [cocoapath setlinewidth:8.0 - (cgfloat)i];         cgfloat tint = (cgfloat)i * 0.15;         nscolor* color = [nscolor colorwithcalibratedred:tint green:tint blue:1.0 alpha:1.0];         [color set];         [cocoapath stroke];     } }  @end

sample output


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