problem with circle.margin

[onmyojiyys]

NK T cells Monocytes B cells Plasma cells NK_pseudo pDCs
1 100 0 0 0 0 0 0
2 0 100 0 0 0 0 0
3 100 0 0 0 0 0 0
4 0 0 100 0 0 0 0
5 0 100 0 0 0 0 0
6 0 0 0 100 0 0 0
7 0 0 0 100 0 0 0
8 0 0 100 0 0 0 0
9 0 100 0 0 0 0 0
10 0 0 0 0 100 0 0
11 0 0 0 0 0 100 0
12 100 0 0 0 0 0 0
13 0 0 100 0 0 0 0
14 0 0 0 0 100 0 0
15 0 0 0 0 0 0 100
16 0 47 0 0 0 0 0

This is my data. When I use the following code to plot and save the image as a PNG, the margins of the image are quite large, with a lot of white space. I wonder if there is any way to address this issue. The 'circle.margin' does not seem to have a very good effect.

png('Circle.png'), width = 4, height = 4, res = 300, units = 'in')
circos.par$circle.margin = c(0.1, 0.1, 0.001, 0.1)
circos.par(gap.after = c(rep(3, nrow(plot_data)-1), 10, rep(3, ncol(plot_data)-1), 10))
chordDiagram(tdata,
grid.col = use_color,
preAllocateTracks = 2,
annotationTrack = c("grid"))
circos.track(
track.index = 2, panel.fun = function(x, y) {
circos.text(
CELL_META$xcenter, CELL_META$ylim[1],
CELL_META$sector.index, facing = "clockwise",
niceFacing = TRUE, adj = c(0, 0.5),
cex = 0.6)
}, bg.border = NA
)
circos.clear()
dev.off()