Client-side: all pixel values from ImageryLayer in Sketch geometry

Question

I’m having trouble chaining this together, but here is what I’d like to accomplish:

* Display a raster as an ImageryLayer from a 3rd-party server (I’ve got this)
* Add the sketch widget and access a polygon the user draws (I think I have this one, too)
* Access the pixel values of all pixels from the raster which are within the user-created polygon
* Calculate/chart data based on the pixel values (check!)

It’s only step 3 that I’m stuck on. Do I somehow need to loop through every pixel in the current extent and test them individually using geometryEngine’s “within” before adding to an array?

I need to do this client-side and can’t perform a server-side rendering rule clip.

I appreciate any help you can provide!

ArnoFiva · Answer

I don't have a running sample at hand, but I believe you should be able to do something like that using the following:

For ImageryLayers: https://developers.arcgis.com/javascript/latest/api-reference/esri-layers-ImageryLayer.html#fetchImage

For TiledImageryLayers: https://developers.arcgis.com/javascript/latest/api-reference/esri-layers-ImageryTileLayer.html#fetchPixels

Use the extent of the sketched geometry as an input for these methods. As you describe above, you could then for each point / pixel in the response use the geometry engine to determine if it is part of the original geometry.

Hope this helps!

DaveMcLaughlin · Answer

Another idea, not sure if this is possible:
Create an ImageryLayer I use just for the analysis (with the same raster source), which then gets clipped with a client-side rendering rule…and then get values of all pixels in that layer after the clip?