ios - Different behaviours for different colors in drawRect: -

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• cgcolorgetcomponents() not returning correct values black , white 1 answer

i puzzled way following code works. expected produce black disk surrounded colored circle. works fine colors (as explained in comments), not others. can explain misterious behaviour?

- (void)drawrect:(cgrect)rect {     cgrect rectangle; cgfloat shiftval=2.0,linewidth=3.0;     rectangle.origin=cgpointmake(shiftval, shiftval);     rectangle.size=self.frame.size;     rectangle.size.width-=shiftval*2;     rectangle.size.height-=shiftval*2;     cgcontextref context = uigraphicsgetcurrentcontext();     cgcontextsetrgbfillcolor(context, 0.0, 0.0, 0.0, 1.0);     cgcontextfillellipseinrect(context, rectangle);      cgcontextsetlinewidth(context, linewidth);      const cgfloat *components = cgcolorgetcomponents([uicolor greencolor].cgcolor); // works expected.     //const cgfloat *components = cgcolorgetcomponents([uicolor darkgraycolor].cgcolor); // no surrounding circle (instead of darkgray).     //const cgfloat *components = cgcolorgetcomponents([uicolor lightgraycolor].cgcolor); // produces greenish circle (instead of lightgray)     // draw outer circle:     cgcontextsetrgbstrokecolor(context,                                components[0],                                components[1],                                components[2],                                components[3]);     cgcontextstrokeellipseinrect(context, rectangle); } 

similar this answer guessing darkgraycolor , lightgraycolor both represent gray-sacle values rather tan rgba-values. , therefore dont have 4 comoponents 2.

you might want / have use different approach of setting color:

cgcontextsetstrokecolorwithcolor(context, [uicolor darkgraycolor].cgcolor);