Composite geospatial image from multiple files

[banesullivan]

Following up on ResonantGeoData/ResonantGeoData#421 (comment)

Would it be possible to have large image use separate TIFs to composite into a single RGB image?

Use case: making an RGB tile server from Landsat images where each band of the raster is in a separate TIF.

A possible workaround: create a VRT for these scenarios, specifying the RGB bands

[manthey]

There are two approaches to this:

(1) create a new "multi" tile source (which would require a file saying how images are composited toegther). This would be like a VRT file but have the flexibility of using any tile source large_image supports.

(2) allow specifying other files as part of the style specification. That is, something like: {bands: [{palette: ['black', 'red']}, {file: <second file>, palette: ['black', 'green']}, {file: <third file>, palette: ['black', 'blue']}]}

The virtue of (1) is that we could construct multi-frame sources fairly intelligently (e.g., you have a time series that you could assemble as frames AND composite different color bands).

The virtue of (2) is the dynamic nature of it and lack of an extra control file. Probably once we implement (1), also supporting (2) will be nearly trivial.

[manthey]

A substantial start to this has been added in #764. It still needs to (a) support general transforms, (b) support cropping, (c) support geospatial data. Ideally, we'd also support an "inline" version of this, so you wouldn't need an explicit source file.

[manthey]

With #1415, the only missing feature is support for geospatial data.

[manthey]

Retitling this to indicate remaining scope.