Preview Images (Thumbnails-STAC)¶

Titiler
Titiler API
Query Parameters
Example Thumbnail
1. Output
2. Create Asset

Titiler ¶

The following Documentation is a step by step guide for how to create stac-thumbnails with titiler.

Titiler API¶

You can test the Titiler API.

Query Parameters¶

The Query parameters are documented under this link.

Example Thumbnail¶

In this example a thumbnail will be created from a GeoTIFF in output format PNG. Furthermore, the GeoTIFF will be reprojected to a different CRS.

import requests
from pyproj import CRS

# Define the endpoint
endpoint = "https://titiler.services.eodc.eu/cog/preview"

# Define the url of the GeoTIFF
url = "https://objectstore.eodc.eu:2222/88346baf22914e828ad2c1763e5e01ff:greenness-austria/2022/greenness_max_id66904_2022.tiff"

# Define input and output CRS
crs_input = CRS.from_epsg(3035).to_wkt()
crs_output = CRS.from_epsg(4326).to_wkt()

# Define the query parameters as a dictionary

# Define "rescale": min, max (min, max values of a Band, e.g. with rasterio --> .min(), .max()) 
# --> rescale is used to normalize image bands, e.g.: bidx: 1, ranges from 0-19, which is not color encoded. 
# Titiler uses this rescaling information to normalize the band values from their original range (0-19) to the 0-255 range, 
# making the image ready for proper visualization.

# Define "nodata": str, int, float (Overwrite internal Nodata value.)
# Define "colormap_name": rio-tiler color map name
# Define "dst_crs": wkt
# Define "coord_crs": wkt

query_parameters = {
    "format": "png", 
    "url": url, #required
    "rescale": "1,19",
    "nodata": "-9999",
    "colormap_name": "greens_r",
    "dst_crs": crs_output,
    "coord_crs": crs_input
}

# Create a Request object
request = requests.Request('GET', endpoint, params=query_parameters)

# Prepare the request
href = request.prepare()

# Print the full URL with the query parameters
print(href.url)

Output¶

output-url

Create Asset¶

Finally add the created titiler url to an asset and add the asset to an item.

import pystac

asset = pystac.Asset(
    href=href,
    media_type=pystac.MediaType.PNG,
    roles=["overview"]
)

item.add_asset(key=asset, asset=asset)