Create multi-panel figure using PNG/JPEG images

Question

Problem: I want to make a multi-panel figure using PNG or JPEG images. The images were not created in R but I want to patch them together in R to form one figure. All the images are the same size/dimensions. What I've tried: ``` library(png) img1 <- readPNG("filepath/img1.png") img2 <- readPNG("filepath/img2.png") library(patchwork) patch <- img1 + img2 patch ``` When I run this, I get the following error: ``` [ reached getOption("max.print") -- omitted 3 matrix slice(s) ] ``` I increased the max print multiple times (to ridiculously high numbers): ``` options(maxprint = 1000000000000) ``` But still get the same error. I then tried making each image into a ggplot (without the points) using: ``` library(ggplot2) img1plot <- ggplot() + background_image(img1) + theme(plot.margin = margin(t=1, l=1, r=1, b=1, unit = "cm")) ``` Which returns the following error: ``` Error in background_image(d311) : could not find function "background_image" ``` Is there another way to patch images together…

Accepted Answer

I'm giving you the couple of alternatives that I Use the most:

Alternative 1: combination of ggplot2, grid and cowplot.

Each of your PNG image can be embedded in a ggplot object using:

```
ggplot2::ggplot() + ggplot2::annotation_custom(grid::rasterGrob(YourPNGimage,
                                                width=ggplot2::unit(1,"npc"),
                                                height=ggplot2::unit(1,"npc")),
                               -Inf, Inf, -Inf, Inf)
```

Then you can use `cowplot::plot_grid()` to arrange your plots.

Alternative 2: using magick package.

The package counts on its own functions to read images, thus we need to tweak your code a bit:

```
img1 <- magick::image_read("filepath/img1.png")
img2 <- magick::image_read("filepath/img2.png")
```

Then using functions like `magick::image_append(c(img1, img2))` you can combine them. See the magick package documentation for more info.

Create multi-panel figure using PNG/JPEG images

Solution

Problem