{
let image_load = img_file != null ?
await img_file.url(img_file)
: await FileAttachment("logarithmic_vs_linear_scale.png").url();
svg.attr("id", "container");
svg.selectAll(".bkg_image").remove();
svg.append("svg:image")
.attr("xlink:href", image_load)
.attr("x", 0)
.attr("y", 0)
.attr("width", image_width)
.attr("class","bkg_image")
.lower();
return image_load;
}