Trying to crop the whitespace (in this case, "transparent space") around a SVG. Not really seeing a simple method to do this. Tried both knitr::plot_crop() and magick::image_trim() but to no avail. The output of both of these methods removes the alpha layer and makes it have a white background.

Example SVG for below:

Knitr method:

knitr::plot_crop("~/Downloads/onions-pd.svg")

produces:

Imagemagick version:

library(magick)
img = image_read("~/Downloads/onions-pd.svg")
img = image_trim(img)
image_write(img,"~/Downloads/onions-pd.svg",format="svg")

produces:

CodePudding user response：

It sounds like you want to crop the viewBox of the svg. There are probably many ways to do this, but one is to work out the new viewBox co-ordinates and write them into the svg file.

We can get the limits of the non-transparent parts like this:

library(magick)

img <- image_read_svg("onions-pd.svg")
data   <- image_data(img) 
opaque <- which(data[4,,] != 0, arr.ind = TRUE)
limits <- paste(paste(apply(opaque, 2, min), collapse = ", "), 
                paste(apply(opaque, 2, max), collapse = ", "), sep = ", ")

limits
#> [1] "11, 64, 417, 440"

and write them into a copy of the svg file like this:

library(xml2)

onions_xml <- read_xml("onions-pd.svg")

xml_set_attr(onions_xml, attr = "viewBox", limits)

write_xml(onions_xml, "onions-cropped.svg")