Geotag an image as a SpatRaster

Geotag an image and return a SpatRaster using coordinates from a supported spatial input class.

rasterpic_img() is an S3 generic. See S3 methods for supported input classes.

Usage

rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...
)

# Default S3 method
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...
)

# S3 method for class 'sf'
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...,
  mask = FALSE,
  inverse = FALSE
)

# S3 method for class 'sfc'
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...,
  mask = FALSE,
  inverse = FALSE
)

# S3 method for class 'sfg'
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...,
  mask = FALSE,
  inverse = FALSE,
  crs = NULL
)

# S3 method for class 'stars'
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...
)

# S3 method for class 'bbox'
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...,
  crs = NULL
)

# S3 method for class 'numeric'
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...,
  crs = NULL
)

# S3 method for class 'SpatRaster'
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...
)

# S3 method for class 'SpatVector'
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...,
  mask = FALSE,
  inverse = FALSE
)

# S3 method for class 'SpatExtent'
rasterpic_img(
  x,
  img,
  halign = 0.5,
  valign = 0.5,
  expand = 0,
  crop = FALSE,
  ...,
  crs = NULL
)

Arguments

x

An R object. See S3 methods for supported classes.

img

An image to geotag. It can be a local file or a URL, for example "https://i.imgur.com/6yHmlwT.jpeg". Accepted file extensions are png, jpg, jpeg, tif and tiff.

halign

A number between 0 and 1 giving the horizontal alignment of img relative to x. 0 aligns img with the left edge of x, 1 aligns it with the right edge and 0.5 centers it horizontally.

valign

A number between 0 and 1 giving the vertical alignment of img relative to x. 0 aligns img with the bottom edge of x, 1 aligns it with the top edge and 0.5 centers it vertically.

expand

An expansion factor of the bounding box of x. 0 means that no expansion is added, 1 means that the bounding box is expanded to double the original size. See Details.

crop

Logical. Should the raster be cropped to the (expanded) bounding box of x? See Details.

...

Further arguments passed to methods.

mask

Logical for vector methods. Should the raster be masked to the shape of x? See Details.

inverse

Logical. Only used when mask = TRUE. If TRUE, areas covered by x are masked instead of areas outside x.

crs

Character string describing a CRS. This parameter only applies when x is a SpatExtent, sfg, bbox or a numeric coordinate vector. See the CRS section.

Value

A SpatRaster object (see terra::rast()) where each layer corresponds to a color channel of img:

• If img has at least 3 layers, the result names layers 1 to 3 "r", "g" and "b" for the red, green and blue channels and names layer 4 "alpha" when applicable.

• If img already has an RGB specification (this may be the case for tif/tiff files), the result keeps that specification.

The resulting SpatRaster will have an RGB specification as explained in terra::RGB().

Details

vignette("rasterpic", package = "rasterpic") explains the effect of parameters halign, valign, expand, crop and mask with examples.

S3 methods

All methods share the parameters, return value and examples documented on this page. rasterpic groups them by input behavior:

• Vector methods for the sf classes sf, sfc and sfg and the terra class SpatVector can mask the image to the input shape.

• Extent-like methods for bbox, numeric coordinate vectors, the stars class stars and the terra classes SpatRaster and SpatExtent use the input bounding box.

• The default method reports unsupported classes. Other packages can provide methods for additional spatial classes.

CRS

This function preserves the CRS of x when applicable. For optimal results, do not use geographic coordinates (longitude/latitude).

crs can be in WKT format, as an "authority:number" code such as "EPSG:4326" or as a PROJ-string such as "+proj=utm +zone=12". It can also be retrieved with:

• sf::st_crs(25830)$wkt.

• terra::crs().

• tidyterra::pull_crs().

See the Value and Notes sections in terra::crs().

See also

vignette("rasterpic", package = "rasterpic") for examples.

From sf:

• sf::st_crs().

• sf::st_bbox().

• vignette("sf1", package = "sf") to understand how sf organizes R objects.

From stars:

• stars::st_as_stars().

From terra:

• terra::vect(), terra::rast() and terra::ext().

• terra::mask().

• terra::crs().

• terra::RGB().

For plotting:

• terra::plot() and terra::plotRGB().

• tidyterra::autoplot.SpatRaster() and tidyterra::geom_spatraster_rgb() with ggplot2.

• tmap, mapsf and maptiles.

Other image geotagging tools: asp_ratio()

Examples

# \donttest{
library(sf)
#> Linking to GEOS 3.12.1, GDAL 3.8.4, PROJ 9.4.0; sf_use_s2() is TRUE
library(terra)
library(ggplot2)
library(tidyterra)
#> 
#> Attaching package: ‘tidyterra’
#> The following object is masked from ‘package:stats’:
#> 
#>     filter

x_path <- system.file("gpkg/UK.gpkg", package = "rasterpic")
x <- st_read(x_path, quiet = TRUE)
img <- system.file("img/vertical.png", package = "rasterpic")

# Use the default configuration.
ex1 <- rasterpic_img(x, img)

ex1
#> class       : SpatRaster
#> size        : 333, 250, 3  (nrow, ncol, nlyr)
#> resolution  : 6484.467, 6484.467  (x, y)
#> extent      : -1193414, 427703.2, 6430573, 8589900  (xmin, xmax, ymin, ymax)
#> coord. ref. : WGS 84 / Pseudo-Mercator (EPSG:3857)
#> source(s)   : memory
#> colors rgb  : 1, 2, 3
#> names       :   r,   g,   b
#> min values  :  15,   8,   4
#> max values  : 254, 255, 254

autoplot(ex1) +
  geom_sf(data = x, fill = NA, color = "white", linewidth = 0.5)


# Expand the bounding box.
ex2 <- rasterpic_img(x, img, expand = 0.5)

autoplot(ex2) +
  geom_sf(data = x, fill = NA, color = "white", linewidth = 0.5)


# Align the image to the left edge.
ex3 <- rasterpic_img(x, img, halign = 0)

autoplot(ex3) +
  geom_sf(data = x, fill = NA, color = "white", linewidth = 0.5) +
  labs(title = "Align")


# Crop to the bounding box.
ex4 <- rasterpic_img(x, img, crop = TRUE)

autoplot(ex4) +
  geom_sf(data = x, fill = NA, color = "white", linewidth = 0.5) +
  labs(title = "Crop")


# Mask to the vector shape.
ex5 <- rasterpic_img(x, img, mask = TRUE)

autoplot(ex5) +
  geom_sf(data = x, fill = NA, color = "white", linewidth = 0.5) +
  labs(title = "Mask")


# Mask outside the vector shape.
ex6 <- rasterpic_img(x, img, mask = TRUE, inverse = TRUE)

autoplot(ex6) +
  geom_sf(data = x, fill = NA, color = "white", linewidth = 0.5) +
  labs(title = "Mask Inverse")


# Combine cropping and inverse masking.
ex7 <- rasterpic_img(x, img, crop = TRUE, mask = TRUE, inverse = TRUE)

autoplot(ex7) +
  geom_sf(data = x, fill = NA, color = "white", linewidth = 0.5) +
  labs(title = "Combine")

# }