how to set color of inserted image in r

Question

Is there a way to insert an image into a plot into R and set its color when I do so? I'd like to insert a silhouette for a given data set and set it to match the color I've chosen for plotting the corresponding the data points. I don't have a strong understanding of how graphics are managed - in computer systems in general, and in R - which may inform the answer to this question.

The code below will insert the image, but I can't figure out a way to change the color.

require(jpeg)
thiscolor <- "red"
plot(x=c(1, 4), y=c(1, 2), main="test plot", col=thiscolor)
thispic <- readJPEG(<insert path for any image here>)
rasterImage(thispic, 
        xleft=3, xright=3.5, 
        ytop=2, ybottom=1.8,
)

Answer 1

Thank you so much!

Because I was using R color names, I had to do a bit of (ungraceful) color conversion. But your code was exactly what I needed! Thank you!

 #convert image to raster 
 thispic.r <- as.raster(thispic)
 #get the hex color
 rgbratios <- col2rgb(thiscolor)/255
 thiscolorhex <- rgb(red=rgbratios[1], 
                         green=rgbratios[2], 
                         blue=rgbratios[3])
 #convert the non-white part of the image to the hex color
 thispic.r[thispic.r!="#FFFFFF"] <- thiscolorhex
 #plot it
 grid.raster(thispic.r, x=xval, y=yval, just="center")

Answer 2

i don't understand exactly what do you mean by silhouette here. But for me a raster is a matrix of color. So you can change its color. here a demonstration. I am using, grid.raster from the grid package. But it the same thing with rasterImage

here an example:

library(png)
library(grid)
img <- readPNG(system.file("img", "Rlogo.png", package="png"))
## convert it to a raster, interpolate =F to select only sample of pixels of img
img.r <- as.raster(img,interpolate=F)
## Change all the white to a blanck
img.r[img.r == "#00000000"] <- 'red'
plot.new()
grid.raster(img.r)