@dhi-gras/terracotta-react
v1.3.1
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React implementation of a context wrapper for abstracting away some of the logic around the Terracotta XYZ tile server.
Terracotta is a pure Python tile server that runs as a WSGI app on a dedicated webserver or as a serverless app on AWS Lambda. It is built on a modern Python 3.6 stack, powered by awesome open-source software such as Flask, Zappa, and Rasterio.
Why Terracotta-react
- Abstracts away the logic around what endpoints you should hit to get the right datasets and display them on a map. All of it through a friendly API.
- Uses the highly performant Deck.gl based on the WebGL framework.
- Includes TypeScript definitions, therefore, it prevents unpredictable type errors when used in your app. The types are available by importing them from the package.
Prerequisites
Check the peerDependencies
of the terracotta-react package.
Usage
Install the package
yarn add @dhi-gras/terracotta-react
// or
npm install @dhi-gras/terracotta-react
TerracottaContextProvider
The context provider aims to offer a few state values and methods to ease the implementation of Terracotta in your project.
import React, { FC } from "react"
import TerracottaProvider from "@dhi-gras/terracotta-react"
const App: FC = () => (
<TerracottaProvider
host={'https://your-terracotta-host.com'} // Without the ending "/".
>
<AppScreen />
</TerracottaProvider>
)
export default App
Hooks
useTerracotta
The hook helps you get the values of the context state through your react tree.
import React, { FC } from "react"
import { useTerracotta } from "@dhi-gras/terracotta-react"
const AppScreen: FC = () => {
const { keys, isLoading, getDatasets } = useTerracotta()
return null;
}
export default AppScreen
Provided state values and methods
keys
An object respective to the response received from the /keys
endpoint of the provided terracotta host.
Example:
[
{
"key": "keyName",
},
{
"key": "keyName",
},
...
]
isLoading
A boolean
value that represents the loading state of the provider. The value changes to true
when making requests to various terracotta endpoints.
getDatasets
A method that returns a Promise by making a call to the /datasets
endpoint. It can take in an argument containing the query parameters used for filtering through the available datasets from the provided Terracotta host.
For example, in the following call, the method will try to query the terracotta datasets for the project_id: 2
including the type: preprocess
and type: postprocess
with that id.
const { getDatasets } = useTerracotta()
const handleDatasets = async () => {
try{
const response = await getDatasets({
project_id: 2,
type: [ 'preprocess', 'postprocess' ]
})
const datasets = response.datasets
return datasets
}catch(err){
console.error(err)
}
}
getMetadata
A method that returns a Promise by making a call to the /metadata
endpoint. It can take in an argument containing one of the datasets from the available dataset list.
const { getMetadata } = useTerracotta()
const handleMetadata = async () => {
try {
const metadata = await getMetadata({ ...dataset })
return metadata
} catch(err) {
console.error(err)
}
}
Deck.gl hooks
This package includes a few helper functions that can be used during the implementation of Terracotta and Deck.gl. This readme file should give you an overview of what hooks are available and how to use them.
useTerracottaLayer
The hook applies the same concept as the useRasterLayer
, and at the same time it wraps up some of the logic around rendering the terracotta raster/s.
The layer can take in more than one dataset and show it on the map, especially when there are multiple tiles to be displayed for the same area of interest.
Usage
import { useTerracottaLayer } from "@dhi-gras/terracotta-react";
const datasets = [
{
"key1": "",
"key2": false,
"key3": 0
},
{
"key1": "",
"key2": true,
"key3": 0
}
]
const terracotta = useTerracottaLayer({
id: 'post-classification-terracotta-layer',
url: https://www.terracotta-deployment.com,
datasets: [ ...datasets ],
type: "singleband",
queryString: "colormap=binary&stretch_range=[0,1]" // Depends on the type of data
...otherTileLayerProps
})
Props
List of specific props related mainly to Terracotta. The rest of the props passed are the same as for the TileLayer and will be applied to the TileLayer.
url
*
The terracotta instance url without the ending "/".
id
*
The unique identifier for the given layer.
datasets
This represents the dataset/s that are to be displayed on the map as TileLayers.
type
The type is related to the type of data that the user would like to render. The options available are 'singleband' and 'rgb'. You can read more about the differences in the official documentation.
queryString
The queryString is used to specify the ranges you would like to see for the Red, Green or Blue band through the r_range, b_range, g_range query parameters.
You can also specify the colormap and the stretch_range in case of 'singleband' or to specify the colors for the categorical data.
useRasterLayer
The package exports a generic layer useRasterLayer
that can be used in conjunction with any type of XYZ server. The layer takes in the same properties as For readming more about it, you can visit the TileLayer documentation.
Usage
import { useRasterLayer } from "@dhi-gras/terracotta-react";
const rasterLayer = useRasterLayer({
id: 'post-classification-terracotta-layer',
data: https://www.terracotta-deployment.com/key1/key2/{z}/{x}/{y}.png,
...otherTileLayerProps
})
Terracotta specific query parameters
In order to render the right colormaps for your data, some specific combination of query parameters must be set.
RGB layers
For rendering RGB layers, we have to specify the following:
- The bands respective to red, green and blue colors.
- The ranges respective to each band.
const rRangeValue = encodeURI([0,1000])
const gRangeValue = encodeURI([0,1000])
const bRangeValue = encodeURI([0,1000])
`.../{z}/{x}/{y}.png?r=B04&g=B03&b=B02&r_range=${rRangeValue}&g_range=${gRangeValue}&b_range=${bRangeValue}`
Singleband layers
For rendering singleband layers, we have the following use-cases
Cateogorical data
For categorical data we must specify:
- The
explicit
colormap - The
explicit_color_map
values
const categoricalColors = encodeURI({ "1": "B9D400", "2": "001BCB" })
`.../{z}/{x}/{y}.png?colormap=explicit&explicit_color_map=${categoricalColors}`
Continuous data
For continuous data we must specify:
- The desired
colormap
from the list of available colormaps. - The
stretch_range
for the range of values to be displayed.
const stretchContinuousColor = encodeURI([0,1])
const continuousColor = 'autumn'
`.../{z}/{x}/{y}.png?colormap=autumn&stretch_range=${stretchContinuousColor}`