---
title: "Raster Layers"
date: "`r format(Sys.time(), '%d %B, %Y')`"
vignette: > 
  %\VignetteIndexEntry{Raster Layers}
  %\VignetteEncoding{UTF-8}
  %\VignetteEngine{knitr::rmarkdown}
output:
  html_document:
    theme:
      version: 5
editor_options: 
  markdown: 
    wrap: 72
---
To see more complete package documentation check out:
<a href="https://pfrater.github.io/arcpullr/">
https://pfrater.github.io/arcpullr/</a>
<hr>
```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
options(rmarkdown.html_vignette.check_title = FALSE)
library(arcpullr)
library(sf)
wi_landcover <- terra::rast(system.file("wi_landcover.png", package = "arcpullr"))
raster_cols <- terra::coltab(wi_landcover)[[1]]
wi_landcover_legend <- 
  wi_landcover_url |>
  get_layer_legend() |>
  match_legend_colors(raster_cols) |>
  dplyr::arrange(.data$value)
attr(wi_landcover, "legend") <- wi_landcover_legend
wi_aerial_imagery <- terra::rast(system.file("wi_aerial_imagery.png", package = "arcpullr"))
```

```{r, echo = FALSE}
#<img src='../man/figures/logo.png' width="160" height="180" style="border: none; float: right"/>
```



`arcpullr` has the capability to query not only vector (Feature) layers, but 
also raster layers (both Map and Image service types). The syntax for these is 
generally the same as for the `get_layer_by_*` family of functions. Map and
Image layers require a bounding box as part of the query, so both 
`get_map_layer` and `get_image_layer` have required arguments of a URL and an 
`sf` object. These functions pull the raster layers provided by the URL and return the layer as a SpatRaster object from the `terra` package.

## URL's for examples 
<a class="btn btn-primary" data-bs-toggle="collapse"href="#collapseExample" role="button" aria-expanded="false" aria-controls="collapseExample">
Example Source Data
</a>
<div class="collapse" id="collapseExample">
  <div class="card card-body"> 
```{r}
# WDNR Server
image_server <- "https://dnrmaps.wi.gov/arcgis_image/rest/services/"

# WI Landcover Type URL
landcover_path <- "DW_Land_Cover/EN_Land_Cover2_Lev2/MapServer"
landcover_url <- paste0(image_server, landcover_path)

# WI Leaf-off Aerial Imagery URL
wi_leaf_off_path <- "DW_Imagery/EN_Image_Basemap_Latest_Leaf_Off/ImageServer"
wi_aerial_imagery_url <- paste0(image_server, wi_leaf_off_path)

# the wis_poly polygon is available as an exported object in arcpullr
```
</div>
</div>
<br>

## Map Layers

The `get_map_layer` function takes a URL and an sf object. Since the query for
this layer type on an ArcGIS REST Service requires a bounding box any sf object
can be used (i.e. POLYGON, POINT, LINE, etc.) and a bounding box will be created 
using the extent of the shape.

The example below pulls Wisconsin landcover types and plots them in a map.

```{r map_layer, eval = FALSE, echo = FALSE}
wi_landcover <- get_map_layer(landcover_url, wis_poly)
```

```{r show_map_plotting, ref.label=c('map_layer', 'plot_map_layer'), eval = FALSE}
```

```{r plot_map_layer, fig.height = 7, fig.width = 7, echo = FALSE}
plot_layer(wi_landcover)
```

## Image Layers


The `get_image_layer` function works the same as `get_map_layer` except that it 
queries from an Image layer. The easiest way to distinguish a Map layer from an 
Image layer is by checking the URL. Those from images will end with 
"ImageServer" whereas those from maps will end with "MapServer". Another way to 
check is to look a the "Supported Operations" at the bottom of the actual web
page on the ArcGIS REST Service. It will say either "Export Image" or 
"Export Map".

This example pulls with Wisconsin Leaf-off Aerial Imagery dataset from the
Wisconsin Department of Natural Resources.

```{r, image_layer, eval = FALSE, echo = FALSE}
wi_aerial_imagery <- get_image_layer(wi_aerial_imagery_url, wis_poly)
```

```{r, plot_image_layer, fig.height = 5, fig.width = 5, echo = FALSE}
plot_layer(wi_aerial_imagery)
```
