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Get started

Source: vignettes/rasterpic.qmd

Getting started with rasterpic is easy: you need an image (png, jpeg/jpg or tif/tiff) and a spatial object from the sf or terra package to begin.

Basic usage

Here we use the shape of Austria as an example:

library(sf)
library(terra)
library(rasterpic)

# Plot.
library(tidyterra)
library(ggplot2)

# Set the shape and image.
x <- read_sf(system.file("gpkg/austria.gpkg", package = "rasterpic"))
img <- system.file("img/vertical.png", package = "rasterpic")

# Create the raster.

default <- rasterpic_img(x, img)

autoplot(default) +
  geom_sf(data = x)
Figure 1: Raster map geotagged with the coordinates of Austria

Options

rasterpic_img() provides several options for expansion, alignment and cropping.

Expand

With this option, the raster extent is expanded beyond the spatial object:

expand <- rasterpic_img(x, img, expand = 1)

autoplot(expand) +
  geom_sf(data = x)
Figure 2: Example image expansion

Alignment

Choose the alignment of the image within the spatial extent:

bottom <- rasterpic_img(x, img, valign = 0)

autoplot(bottom) +
  geom_sf(data = x)
Figure 3: Example image alignment

Crop and mask

Crop and mask the image:

mask <- rasterpic_img(x, img, crop = TRUE, mask = TRUE)

autoplot(mask)

maskinverse <- rasterpic_img(x, img, crop = TRUE, mask = TRUE, inverse = TRUE)

autoplot(maskinverse)
Figure 4: Example of masked image
Figure 5: Example of inverse masked image

Supported spatial objects for geotagging

  • Spatial objects of the sf package: sf, sfc, sfg or bbox.
  • Spatial objects of the terra package: SpatRaster, SpatVector and SpatExtent.
  • A numeric coordinate vector of the form c(xmin, ymin, xmax, ymax).

Supported image formats

rasterpic can parse the following image formats:

  • png files.
  • jpg/jpeg files.
  • tif/tiff files.