ggplot2qgis

https://github.com/yutannihilation/ggplot2qgis
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ggplot2qgis exports ggplot2-based map plots and tmap maps into QGIS project (.qgs) files, preserving...
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### Install ggplot2qgis from R-universe

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Use this command to install the package from the official R-universe repository.

```r
install.packages("ggplot2qgis", repos = c("https://yutannihilation.r-universe.dev", "https://cloud.r-project.org"))
```

--------------------------------

### Define Paletted Raster Renderer Palette Entries

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/docs/qgs-format.md

Example of the colorPalette structure used for unique value rendering in QGIS raster layers.

```xml
<colorPalette>
  <paletteEntry alpha="255" color="#e41a1c" label="forest" value="1"/>
  <paletteEntry alpha="255" color="#377eb8" label="water"  value="2"/>
</colorPalette>
```

--------------------------------

### Exporting tmap objects to QGIS

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/man/write_qgs.Rd

Use this snippet to save a tmap object as a QGIS project file. Requires the tmap package to be installed and loaded.

```R
if (requireNamespace("tmap", quietly = TRUE)) {
  x <- tmap::tm_shape(nc) + tmap::tm_polygons(fill = "AREA")
  write_qgs(x, tempfile(fileext = ".qgs"))
}
```

--------------------------------

### Render a QGIS project to PNG

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/tools/qgis/README.md

Executes the rendering script to convert a .qgs project file into a PNG image.

```sh
tools/qgis/render_project.py project.qgs out.png
```

--------------------------------

### Structure of a .qgs XML file

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/docs/qgs-format.md

The root element contains project metadata, layer tree definitions, and individual map layer configurations.

```xml
<!DOCTYPE qgis PUBLIC 'http://mrcc.com/qgis.dtd' 'SYSTEM'>
<qgis projectname="" saveDateTime="..." saveUser="..." saveUserFull="..." version="4.2.0-Belém do Pará">
  ... project-wide settings ...
  <layer-tree-group> ... layer tree entries ... </layer-tree-group>
  ...
  <projectlayers>
    <maplayer type="raster"> ... </maplayer>   <!-- XYZ tiles or a local raster file (e.g. .tif) -->
    <maplayer type="vector"> ... </maplayer>   <!-- .gpkg layer -->
  </projectlayers>
  <layerorder> ... </layerorder>
  ... more project-wide settings ...
</qgis>
```

--------------------------------

### Run script with QGIS environment

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/tools/qgis/README.md

Uses the qgis-python wrapper to execute a script within the QGIS Python environment.

```sh
tools/qgis/qgis-python probe.py project.qgs
```

--------------------------------

### Generate marker shapes reference

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/tools/qgis/README.md

Draws QGIS SimpleMarker shapes to a PNG file for reference and measurement.

```sh
tools/qgis/marker_shapes.py --png shapes.png
```

--------------------------------

### Compare R plot with QGIS rendering

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/tools/qgis/README.md

Demonstrates the workflow for comparing an R-generated plot with a QGIS-rendered project file.

```sh
# The R side: write the project and render the same plot to a PNG.
Rscript -e 'write_qgs(map, "map.qgs"); png("r.png", 1200, 800, res = 96); print(map); dev.off()'

# The QGIS side, at the same size and resolution.
tools/qgis/render_project.py map.qgs qgis.png --size 1200x800 --dpi 96
```

--------------------------------

### write_qgs(x, filename)

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/man/write_qgs.Rd

Writes a spatial object to a QGIS project file.

```APIDOC
## write_qgs

### Description
Exports a spatial object to a QGIS project file (.qgs).

### Parameters
- **x** (object) - The spatial object to be exported (e.g., a tmap object).
- **filename** (string) - The file path where the .qgs file should be saved.

### Example
```r
if (requireNamespace("tmap", quietly = TRUE)) {
  x <- tmap::tm_shape(nc) + tmap::tm_polygons(fill = "AREA")
  write_qgs(x, tempfile(fileext = ".qgs"))
}
```
```

--------------------------------

### Adding a basemap to QGIS export

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Include a basemap in the exported QGIS project by specifying a key or URL template in the write_qgs function.

```r
write_qgs(p, "nc.qgs", basemap = "osm")
```

--------------------------------

### Measure rendered features

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/tools/qgis/README.md

Renders a specific extent and measures the output dimensions in pixels and millimeters.

```sh
tools/qgis/render_project.py one.qgs one.png \
    --size 800x800 --extent=-80,34,-78,36 --measure
#> drawn: 22x22 px (5.82x5.82 mm at 96 dpi)
```

--------------------------------

### write_qgs(plot, path, ...)

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/man/write_qgs.Rd

Converts a ggplot2 plot into a QGIS project file. The data for each layer is saved as a GeoPackage or GeoTIFF, and the layer is styled based on the plot's color scales and aesthetics.

```APIDOC
## write_qgs

### Description
Converts a ggplot2 plot into a QGIS project (.qgs) file. The function maps ggplot2 layers (sf objects, SpatRaster) to QGIS layers and translates aesthetics into QGIS renderers.

### Parameters
- **plot** (ggplot) - The ggplot2 object to convert.
- **path** (character) - The file path for the output .qgs file.
- **...** (dots) - Additional arguments passed to methods.

### Returns
- **path** (character) - The path to the created .qgs file, returned invisibly.
```

--------------------------------

### write_qgs

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/man/write_qgs.Rd

Exports a ggplot2 or tmap object to a QGIS project file.

```APIDOC
## write_qgs(plot, path, ...)

### Description
Writes a ggplot2 or tmap object as a QGIS project file. This function handles the conversion of map layers and styling into a format compatible with QGIS.

### Parameters
- **plot** (object) - Required - A ggplot2 or tmap object.
- **path** (string) - Required - The file path where the .qgs file will be saved.
- **use_plot_crs** (boolean) - Optional - Whether to use the plot's CRS (default: TRUE for tmap, FALSE for ggplot).
- **gradient_style** (string) - Optional - How to render continuous scales: 'graduated' or 'continuous'.
- **overwrite** (boolean) - Optional - Whether to overwrite an existing file (default: FALSE).
- **layer_names** (character vector) - Optional - Custom names for the layers.
- **basemap** (string) - Optional - An XYZ tile layer URL or predefined key (e.g., 'osm').
- **create_na_layer** (boolean) - Optional - Whether to create an NA layer (tmap specific, default: TRUE).
```

--------------------------------

### Export tidyterra pseudocolor raster to QGIS

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Creates a single-band pseudocolor layer in QGIS that reproduces the continuous fill scale from a tidyterra plot.

```r
library(tidyterra)

volcano2 <- terra::rast(system.file("extdata/volcano2.tif", package = "tidyterra"))

p <- ggplot() +
  geom_spatraster(data = volcano2) +
  scale_fill_whitebox_c()

write_qgs(p, "volcano.qgs")
```

--------------------------------

### Exporting tmap objects to QGIS

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Export tmap objects to QGIS, preserving color scales and basemaps defined in the tmap object.

```r
library(tmap)

x <- tm_basemap("OpenStreetMap") +
  tm_shape(nc) +
  tm_polygons(fill = "AREA")

write_qgs(x, "nc_tmap.qgs")
```

--------------------------------

### Export tidyterra filled contours to QGIS

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Creates a polygon layer where each contour band is represented as a feature with a categorized renderer.

```r
p <- ggplot() +
  geom_spatraster_contour_filled(data = volcano2) +
  geom_spatraster_contour(data = volcano2)

write_qgs(p, "volcano_bands.qgs")
```

--------------------------------

### Export tmap raster to QGIS

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Converts tmap raster objects into QGIS raster layers, preserving classes, colors, and legend labels.

```r
library(stars)

data(land, package = "tmap")

x <- tm_shape(land) + tm_raster("cover")

write_qgs(x, "land.qgs")
```

--------------------------------

### Export tidyterra contour labels to QGIS

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Produces a line layer with QGIS labeling enabled, using custom label formatting.

```r
p <- ggplot() +
  geom_spatraster_contour_text(
    data = volcano2,
    label_format = scales::label_number(suffix = " m")
  )

write_qgs(p, "volcano_contour_text.qgs")
```

--------------------------------

### Export tidyterra contour lines to QGIS

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Generates a GeoPackage-backed line layer where contour values are preserved as attributes.

```r
p <- ggplot() +
  geom_spatraster(data = volcano2) +
  geom_spatraster_contour(data = volcano2, aes(colour = after_stat(level)))

write_qgs(p, "volcano_contour.qgs")
```

--------------------------------

### Exporting tidyterra SpatVector to QGIS

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Export spatial data visualized with tidyterra's geom_spatvector to a QGIS project.

```r
library(tidyterra)

cyl <- terra::vect(system.file("extdata/cyl.gpkg", package = "tidyterra"))

p <- ggplot(cyl) +
  geom_spatvector(aes(fill = name))

write_qgs(p, "cyl.qgs")
```

--------------------------------

### Exporting ggplot2 sf objects to QGIS

Source: https://github.com/yutannihilation/ggplot2qgis/blob/main/README.md

Use write_qgs to export a ggplot2 object containing geom_sf layers to a QGIS project file.

```r
library(ggplot2)
library(ggplot2qgis)

nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)

p <- ggplot(nc) +
  geom_sf(aes(fill = AREA))

write_qgs(p, "nc.qgs")
```
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