Measure Ink Area

Question

I read about the relationship between data and Tufte ink, and I was wondering if it is possible to measure the amount of “ink” that the plot uses?

If this is not possible in R, perhaps with another tool like GIMP or imagemagick?

Answer 1

I would suggest using grid.cap() to convert the contents of the graphics device to bitmap, and then just calculate the fraction of non-white pixels (in other words, “ink”). In the following example, in order to focus the calculations on the ink in the graph area, I set par(mar=c(0,0,0,0)) , but you can drop this line if you want to also study the amount of ink in the axes, ticks, axis labels, header, etc.

 library(grid) ## Plot to R default graphical device opar <- par(mar=c(0,0,0,0)) plot(rnorm(1e4), rnorm(1e4), pch=16) ## Capture contents of the graphics device as a raster (bitmap) image p <- grid.cap() ## Compute the proportion of pixels that are not white (ie are inked in) sum(p!="white")/length(p) # [1] 0.2414888 ## Restore pre-existing graphical parameters par(opar)