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How can I make a built-in palette in EE apply to all bands of an Image(), not just a specific one?

Context: I am using Google EarthEngine to display data from the Cropland Data Layer (CDL), which is a cropmap. Typical CDL images come with a band cropland, which has a built-in colour palette (showing the same colour scheme as the original CDL).

The problem: Now when I do a conversion from "Image Collection with many images, each including cropland" to "Image with multiple cropland bands, where the name of the band represents the year", I loose the colour attributes! Ironically, if I were to rename a specific band to cropland when visualising, the palette will come back.

This seems to suggest that the palette is associated to a specific band name (indeed, it shows up in properties as: cropland_class_names).

How can I make the palette apply to any band in the Image, with arbitrary band name?

Code:

var CDL_12 = ee.Image('USDA/NASS/CDL/2012')
var CDL_13 = ee.Image('USDA/NASS/CDL/2013')
var CDL_12_13 = CDL_12.select("cropland").rename("CDL_2012").
  addBands(CDL_13.select("cropland").rename("CDL_2013"))

print(CDL_12_13, "CDL_12_13")

First one (untouched) will show the right colours. Second (band renamed), won;t, while third (renamed band name dback to cropland) will show right again:

Map.addLayer(CDL_12.select("cropland"), {}, "CDL 2012 raw")
Map.addLayer(CDL_12_13.select("CDL_2012"), {}, "CDL 2012 from Image")
Map.addLayer(CDL_12_13.select("CDL_2012").rename("cropland"), {}, "CDL 2012 from Image: works")
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You can apply the palette manually using image.visualize(), however if the values that the colors match aren't contiguous, you'll need to remap them to be contiguous.

var CDL_12 = ee.Image('USDA/NASS/CDL/2012')

var palette = ee.List(CDL_12.get("cropland_class_palette"))
var values = ee.List(CDL_12.get("cropland_class_values"))
var sequence = ee.List.sequence(0, values.size().subtract(1))

var colorized = CDL_12.remap(values, sequence).visualize({palette: palette})
Map.addLayer(colorized)
  • thanks! I still don't understand fully why it works directly on the original CDL, but not the transformed/renamed? Is there not a simple way to say that a palette corresponds to multiple bands, without the need to remap each band individually? – Matifou Dec 5 '18 at 17:06

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