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Convert an image into a geotagged SpatRaster

Source: R/rasterpic_img.R
rasterpic_img.Rd

Geotags an image based on the coordinates of a spatial object.

rasterpic_img() is an S3 generic. rasterpic provides methods for the following classes:

  • SpatExtent

  • SpatRaster

  • SpatVector

  • bbox

  • default

  • numeric

  • sf

  • sfc

  • sfg

  • stars

Usage

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).

img

An image to be geotagged. It can be a local file or a URL (e.g. "https://i.imgur.com/6yHmlwT.jpeg"). Accepted extensions are png, jpeg/jpg and tiff/tif.

halign

A number between 0 and 1 giving the horizontal alignment of img relative to x. 0 aligns x with the left edge, 1 aligns 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 x with the bottom edge, 1 aligns 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, available for vector methods. Should the raster be masked to the shape of x? See Details.

inverse

Logical. This only has an effect when mask = TRUE. If TRUE, areas of the raster covered by x are masked.

crs

Character string describing a CRS. This parameter only applies when x is a SpatExtent, sfg, bbox or a numeric coordinate vector. See 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 will have an additional property setting layers 1 to 3 as the red, green and blue channels with names "r", "g" and "b" and alpha if applicable.

  • If img already has a definition of RGB values (this may be the case for tiff/tif files) the result will keep that channel definition.

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

Details

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

S3 methods

rasterpic supports the following input classes:

  • sf classes: sf, sfc, sfg or bbox.

  • terra classes: SpatRaster, SpatVector and SpatExtent.

  • stars classes: stars.

  • A numeric coordinate vector of the form c(xmin, ymin, xmax, ymax).

Other packages can provide methods for additional spatial classes.

Methods for extent-like inputs use the object extent. Methods for vector inputs can also mask the image to the object shape.

CRS

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

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

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

See also

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

From sf:

From stars:

From terra:

For plotting:

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")

# 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.
ex2 <- rasterpic_img(x, img, expand = 0.5)

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


# Align.
ex3 <- rasterpic_img(x, img, halign = 0)

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

labs(title = "Align")
#> <ggplot2::labels> List of 1
#>  $ title: chr "Align"

# Crop.
ex4 <- rasterpic_img(x, img, crop = TRUE)

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


# Mask.
ex5 <- rasterpic_img(x, img, mask = TRUE)

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


# Inverse mask.
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 inverse masking and cropping.
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")

# }