Removing frame/plot borders from output

I am plotting point density using theplot.imcommand in spatstat, and my output always has a frame around the plotted image that becomes thicker when I increase resolution for export. I triedframe=F,axes=F,plot.frame=FALSE,bty='n'but none of them seem to fix the issue. Anyone know a solution to this?

Usebox=FALSE(see? argument box, a logical value specifying whether a box should be drawn.):

Z <- setcov(owin()) tc <- colourmap(rainbow(128), breaks=seq(-1, 2, length=129)) plot(Z, col=tc)

plot(Z, col=tc, box=FALSE)