s=Import["spinavy.jpg"];

ss=Blur[s]

ListLogPlot[ImageLevels[ss],Joined->True,PlotStyle->{Red,Green,Blue}]

f[{r_,g_,b_}]:=If[r>0.5,{1,1,1},{r,g,b}]

c=ImageApply[f,ss]

Export["cisty.jpg",c];