Output Destinations

Note

Output destinations control where results are stored – like a download link versus the DL Catalog. You can use output formats, which control how the results are stored, in conjunction with output destinations.

For example, with destination='email' you might use format='geotiff' or format='json'. Both would send emails; the emails would have links to download data in GeoTIFF versus JSON format.

Some destinations can only be used with certain formats. For example, with the Catalog destination, you can only use the GeoTIFF format.

When calling compute, you can pick the destination for the results using the destination argument.

If you don’t need to supply any options for the destination, you can use the destination’s shorthand:

>>> two = wf.Int(1) + 1
>>> two.compute(destination="download")

If you would like to provide more destination options, you pass the destination as a dictionary:

>>> two = wf.Int(1) + 1
>>> two.compute(destination={"type": "email", "subject": "My Computation is Done"})

Note that when passing the destination as a dictionary, it must include a type key with the destination’s name.

Available Destinations

The following is a list of the available destinations and their options. The keys in the destination dictionary must match the keys listed here.

Download

Shorthand: "download"

Download (the default) stores a result (in any format) and gives you a link to download it. The link is valid for 10 days after job completion, then the data is automatically deleted. Download is good for getting results back locally, whether to continue using results in Python (with the pyarrow format) or save results to disk (with formats like geotiff).

Options

  • No options

Compatible Formats

Examples

>>> two = wf.Int(1) + 1
>>> two.compute(destination="download")
1
>>> two.compute(destination="download", format="json")
b'1'

Email

Shorthand: "email"

Email is equivalent to Download, but also sends you an email when the job is done. The email contains a link to download the data. Anyone with that link can download the data, so be careful forwarding it. As with Download, the link will expire after 10 days.

Options

  • subject, str, default “Your job has completed”: The subject of the email. Always prefixed with Workflows:.

  • body, str, default “Your Workflows job is done.”: The body of the email.

Compatible Formats

  • All formats. However, widely-used formats like JSON or GeoTIFF usually make the most sense for email. With formats like MsgPack and especially PyArrow, you’d have to write code to parse the data, instead of clicking the download link and getting a file you can easily work with.

Examples

>>> two = wf.Int(1) + 1
>>> two.compute(destination="email", format="json")
>>> two = wf.Int(1) + 1
>>> two.compute(destination={"type": "email", "subject": "My Computation is Done"}, format="json")

Catalog

Shorthand: a catalog.Image

Uploads a Workflows Image to the Catalog. Can only be used when computing a Workflows Image.

Image.compute or Job.result with this destination will just return the catalog.Image object, not the data uploaded.

Options

Usually, you should set rescale=True and change_dtype=True. However, since they can change your data in unexpected ways, they are off by default.

  • image, catalog.Image: The Catalog Image object to upload to.

  • overwrite, bool, default False: Overwrites the image if it already exists.

  • rescale, bool, default False: Rescales pixel values in each band from physical_range to data_range, only if physical_range is set for the band. (When loading imagery, Workflows automatically rescales values into physical_range, so this reverses that.)

  • change_dtype, bool, default False: changes the data type of the uploaded array to match the data type of the Product. Usually combined with rescale. (When loading imagery, Workflows converts to float64, so this undoes that.)

    Beware of data loss before setting change_dtype: whether with rescale, Image.scale_values, or plain arithmetic, be sure the values can be represented in the Product’s data type. For example, if the product in Catalog was uint16, and your Workflows Image currently held float64 values from 0.0 to 1.0, converting those to uint16 would just give you only 0s and 1s, so you’d want to rescale to a range like 0-10000 first to avoid data loss.

Transformations

Workflows does a number of transformations to make your Workflows Image compatible with the Catalog, such as reordering bands to match by name, rescaling and changing dtype, if requested, and using the Image’s mask to fill in nodata values and generate an alpha band. Here are the full details:

  • If acquired is not already set on the catalog.Image you pass, it’s taken from properties['date'] on the Workflows Image, or if that’s also not set, then from the current timestamp.

  • Reorders the Workflows Image bands to the product’s band order, matching by band name. If the names don’t match, assumes the bands are already in order.

  • If rescale is True: Rescales pixel values from physical_range to data_range, for each band where physical_range is set.

  • If change_dtype is True: Converts to the Product’s dtype.

  • Fills in nodata values from the Image’s mask, for bands with a nodata value.

  • Create an alpha band from the Image’s mask if:

    • The Product has exactly 1 alpha band, which must be a MaskBand with is_alpha set to True.

    • The Workflows Image doesn’t have a band for alpha (it has one less band than the product, and doesn’t have a band with the alpha band’s name).

Requirements

  • The Workflows Image must have the same number (and ideally same names) of bands as the Catalog Product you’re uploading to (except an alpha band, which is generated automatically).

  • All the bands in the Catalog Product must have the same data type.

  • The Catalog Product must either have an alpha band (a MaskBand with is_alpha set to True), or every band must have a nodata value set (nodata is preferrable).

  • You must have write access to the Product.

Compatible Formats

  • Only GeoTIFF. Though if you don’t set format= and it defaults to pyarrow, it’s automatically switched to GeoTIFF for you. To control the details of the GeoTIFF that’s uploaded to Catalog (overviews, overview resampler, etc.), specify format={"type": "geotiff", ...} with the parameters you want.

Examples

>>> import descarteslabs as dl
>>> import descarteslabs.workflows as wf
>>> composite = (
...     wf.ImageCollection.from_id("sentinel-1:GRD", "2020-01-01", "2020-05-01")
...     .mean(axis="images")
... )

Assume the product org:my_product_id already has the same bands as composite (in this case, vv and vh), and the bands have nodata values set.

We can upload a single Catalog Image:

>>> image = dl.catalog.Image(name="my_image", product_id="org:my_product_id")
>>> tile = dl.scenes.DLTle.from_latlon(35.6870, -105.9378, 10, 1024, 0)
>>>
>>> composite.compute(tile, destination=image)
Job ID: 8b21474899b177431d404e42e25a958cc32302af37646f7e
[######] | Steps: 21/21 | Stage: SUCCEEDED
Image: my_image
  id: org:my_product_id:my_image
  product: org:my_product_id
  created: Wed Jan  1 12:00:00 2020

Or, if you need to set options:

>>> composite.compute(
...     tile,
...     destination={
...         "type": "catalog",
...         "image": image,
...         "overwrite": True,
...         "rescale": True,
...         "change_dtype": True,
...     },
... )

More commonly, you’d upload many Images by splitting the area into tiles and launching concurrent upload Jobs:

>>> tiles = dl.scenes.DLTile.from_shape(aoi_geometry, 10, 1024, 0)
>>> images = [dl.catalog.Image(name=tile.key.replace(":", "_"), product_id="org:my_product_id") for tile in tiles]
>>> jobs = [composite.compute(tile, destination=image, block=False) for tile, image in zip(tiles, images)]