image=;

(blurDiff=ImageDifference[image,Blur[image,2]])//ImageAdjust

edges=EdgeDetect[blurDiff,1]

dilation=Dilation[edges,1]

filled=FillingTransform[dilation]

b=Erosion[filled,1]

skel=SkeletonTransform[b]

b2=InverseDistanceTransform@ImageMultiply[skel,Binarize[skel,2]]

mask=DeleteSmallComponents[b2]

SetAlphaChannel[image,mask]