%?Region?based?Active?Contour?Segmentation
%
%?seg?=?region_seg（Iinit_maskmax_itsalphadisplay）
%
%?Inputs:?I???????????2D?image
%?????????init_mask???Initialization?（1?=?foreground?0?=?bg）
%?????????max_its?????Number?of?iterations?to?run?segmentation?for
%?????????alpha???????（optional）?Weight?of?smoothing?term
%???????????????????????higer?=?smoother.??default?=?0.2
%?????????display?????（optional）?displays?intermediate?outputs
%???????????????????????default?=?true
%
%?Outputs:?seg????????Final?segmentation?mask?（1=fg?0=bg）
%
%?Description:?This?code?implements?the?paper:?“Active?Contours?Without
%?Edges“?By?Chan?Vese.?This?is?a?nice?way?to?segment?images?whose
%?foregrounds?and?backgrounds?are?statistically?different?and?homogeneous.
%
%?Example:
%?img?=?imread（‘tire.tif‘）;
%?m?=?zeros（size（img））;
%?m（33:33+11744:44+128）?=?1;
%?seg?=?region_seg（imgm500）;
%
%?Coded?by:?Shawn?Lankton?（www.shawnlankton.com）
%------------------------------------------------------------------------
function?seg?=?region_seg（Iinit_maskmax_itsalphadisplay）
??
??%--?default?value?for?parameter?alpha?is?.1
??if（~exist（‘alpha‘‘var‘））?
????alpha?=?.2;?
??end
??%--?default?behavior?is?to?display?intermediate?outputs
??if（~exist（‘display‘‘var‘））
????display?=?true;
??end
??%--?ensures?image?is?2D?double?matrix
??I?=?im2graydouble（I）;????
??
??%--?Create?a?signed?distance?map?（SDF）?from?mask
??phi?=?mask2phi（init_mask）;
??
??%--main?loop
??for?its?=?1:max_its???%?Note:?no?automatic?convergence?test

????idx?=?find（phi?<=?1.2?&?phi?>=?-1.2）;??%get?the?curve‘s?narrow?band
????
????%--?find?interior?and?exterior?mean
????upts?=?find（phi<=0）;?????????????????%?interior?points
????vpts?=?find（phi>0）;??????????????????%?exterior?points
????u?=?sum（I（upts））/（length（upts）+eps）;?%?interior?mean
????v?=?sum（I（vpts））/（length（vpts）+eps）;?%?exterior?mean
????
????F?=?（I（idx）-u）.^2-（I（idx）-v）.^2;?????????%?force?from?image?information
????curvature?=?get_curvature（phiidx）;??%?force?from?curvature?penalty
????
????dphidt?=?F./max（abs（F））?+?alpha*curvature;??%?gradient?descent?to?minimize?energy
????
????%--?maintain?the?CFL?condition
????dt?=?.45/（max（dphidt）+eps）;
????????
????%--?evolve?the?curve
????phi（idx）?=?phi（idx）?+?dt.*dphidt;

????%--?Keep?SDF?smooth
????phi?=?sussman（phi?.5）;

????%--?intermediate?output
????if（（display>0）&&（mod（its20）?==?0））?
??????showCurveAndPhi（Iphiits）;??
????end
??end
??
??%--?final?output
??if（display）
????showCurveAndPhi（Iphiits）;
??end
??
??%--?make?mask?from?SDF
??seg?=?phi<=0;?%--?Get?mask?from?levelset

??
%---------------------------------------------------------------------
%---------------------------------------------------------------------
%--?AUXILIARY?FUNCTIONS?----------------------------------------------
%---------------------------------------------------------------------
%---------------------------------------------------------------------
??
??
%--?Displays?the?image?with?curve?superimposed
function?showCurveAn

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件???????7871??2008-09-04?10:43??主動輪廓模型分割程序\airplane.jpg

?????文件???????6207??2008-09-04?10:43??主動輪廓模型分割程序\region_seg.m

?????文件????????618??2008-09-04?10:45??主動輪廓模型分割程序\region_seg_demo.m

?????目錄??????????0??2012-11-09?10:35??主動輪廓模型分割程序

-----------?---------??----------?-----??----

????????????????14696????????????????????4