kernel density - R: Shift of resulting image after kernel2d -


i've strange problem after applying kernel2d r code on images. resulting density plot shifted several pixels (up & right side). load image, threshold (until images overlapping). generate list of pixels > 0. 

listpospixels=which(thiv>0, arr.ind = true);

which serves input kernel2d function. w , height set dimensions of input image. h i've chosen different values seem not correlated shifts. 

res <- kernel2d(as.points(listpospixels), poly=cbind(c(0,    d[1], d[1],     0),                                                       c(0,       0, d[2], d[2])),                 h0=h, nx=w, ny=height);

the image stored png

png(paste('kerneldensity.png', sep=''), width=w, height=height) par(mar=c(0,0,0,0)) contour(res, add=f, drawlabels=f, col='green',xaxt='n', yaxt='n')

any hints? thanks! durin

full code example:

library(ebimage) require(splancs)   options(max.contour.segments=50000); thiv<-readimage('shiftedinput.jpg'); thiv<-flip(thiv); #due plotting listpospixels=which(thiv>0, arr.ind = true); d=dim(thiv); w <-d[1]; height <- d[2]; res <- kernel2d(as.points(listpospixels), poly=cbind(c(0,    d[1], d[1],     0),                                                       c(0,       0, d[2], d[2])),                 h0=20, nx=w, ny=height);  png(paste('kerneldensity.png', sep=''), width=w, height=height) par(mar=c(0,0,0,0)) contour(res, add=f, drawlabels=f, col='green',xaxt='n', yaxt='n') dev.off()

input image code above

example image


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