Adding custom images to ggplot facets

Question

I'd like to add a custom image to each facet. Using annotation_custom duplicates an image across all facets, e.g:

require(ggplot2); require(grid); require(png); require(RCurl)

p = ggplot(iris, aes(Sepal.Length, Sepal.Width)) + geom_point() + facet_wrap(~Species)

img1 = readPNG(getURLContent('https://cdn2.iconfinder.com/data/icons/animals/48/Turtle.png'))
img2 = readPNG(getURLContent('https://cdn2.iconfinder.com/data/icons/animals/48/Elephant.png'))
img3 = readPNG(getURLContent('https://cdn2.iconfinder.com/data/icons/animals/48/Hippopotamus.png'))

a1 = annotation_custom(rasterGrob(img1, interpolate=TRUE), xmin=7, xmax=8, ymin=3.75, ymax=4.5)
a2 = annotation_custom(rasterGrob(img2, interpolate=TRUE), xmin=7, xmax=8, ymin=3.75, ymax=4.5)
a3 = annotation_custom(rasterGrob(img3, interpolate=TRUE), xmin=7, xmax=8, ymin=3.75, ymax=4.5)

p + a1

Is there an alternative method to achieve this so img1-3 populate the respective facets correctly?

You could use the annotation_custom2 function by @baptiste. See https://stackoverflow.com/questions/32807665/removing-one-tablegrob-when-applied-to-a-box-plot-with-a-facet-wrap?answertab=votes#tab-top — Edgar Santos, Jun 22 '17 at 01:52
Also, this might be useful https://github.com/hrbrmstr/ggalt/issues/4 — Edgar Santos, Jun 22 '17 at 01:53
Neat hack by @baptiste. Thanks for link. Want to chalk up the answer? My line is `a1 = annotation_custom2(rasterGrob(img1, interpolate=TRUE), xmin=7, xmax=8, ymin=3.75, ymax=4.5, data=iris[1,])` — geotheory, Jun 22 '17 at 09:14

Edgar Santos · Accepted Answer · 2017-07-04T21:09:18.190

For completeness, I'm adding the answer. All credit goes to @baptiste who suggested the annotation_custom2 function.

require(ggplot2); require(grid); require(png); require(RCurl)

p = ggplot(iris, aes(Sepal.Length, Sepal.Width)) + geom_point() + facet_wrap(~Species)

img1 = readPNG(getURLContent('https://cdn2.iconfinder.com/data/icons/animals/48/Turtle.png'))
img2 = readPNG(getURLContent('https://cdn2.iconfinder.com/data/icons/animals/48/Elephant.png'))
img3 = readPNG(getURLContent('https://cdn2.iconfinder.com/data/icons/animals/48/Hippopotamus.png'))


annotation_custom2 <- 
function (grob, xmin = -Inf, xmax = Inf, ymin = -Inf, ymax = Inf, data){ layer(data = data, stat = StatIdentity, position = PositionIdentity, 
        geom = ggplot2:::GeomCustomAnn,
        inherit.aes = TRUE, params = list(grob = grob, 
                                          xmin = xmin, xmax = xmax, 
                                          ymin = ymin, ymax = ymax))}

a1 = annotation_custom2(rasterGrob(img1, interpolate=TRUE), xmin=7, xmax=8, ymin=3.75, ymax=4.5, data=iris[1,])
a2 = annotation_custom2(rasterGrob(img2, interpolate=TRUE), xmin=7, xmax=8, ymin=3.75, ymax=4.5, data=iris[51,])
a3 = annotation_custom2(rasterGrob(img3, interpolate=TRUE), xmin=7, xmax=8, ymin=3.75, ymax=4.5, data=iris[101,])

p + a1 + a2 + a3

Output:

@ed_sans and baptiste, this solution doesn't work when using scale_x_reverse() or scale_x_continuous(trans = "reverse"). The images just don't show up. Is there a fix for this? — Roger, Mar 07 '19 at 10:48

Adding custom images to ggplot facets

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