gee-blend

Jesse Anderson

About

gee-blend is a code module for using blended visualizations in Google Earth Engine. It can be loaded in the playground by clicking here, which will add the repository containing the code to the Reader section of the Scripts tab, under users/jja/public. The script blend_demo.js illustrates some of its basic functionality.

Using the Module

You can load the module in your code by running

var blend = require('users/jja/public:blend.js');

Blend functions can be applied using the following pattern: blend.<function>(top_image, bottom_image); Where <function> is one of the following:

• addition
• burn
• darken
• difference
• dodge
• hard_light
• lighten
• multiply
• normal
• overlay
• screen
• subtract

`

Here is an example blend operation and output.

Code:

// First, add the module to your account by going to https://code.earthengine.google.com/?accept_repo=users/jja/public

// Load the module
var blend = require('users/jja/public:blend.js');

// Load and visualize a digital elevation model
var dem = ee.Image("CGIAR/SRTM90_V4");
var dem_rgb = dem.visualize({
  min:100, 
  max:6000, 
  palette: ['#000004', '#50127b', '#b63679', '#fc8761', '#fdfd65'],
  forceRgbOutput:true
});

// Derive and visualize a slope image
var slope_rgb = ee.Terrain.slope(dem).visualize({
  min:0, 
  max:90, 
  palette: ['#000000', '#ffffff'],
  forceRgbOutput:true
});

// Use the `difference` blend function and add to the map
Map.addLayer(blend.difference(dem_rgb, slope_rgb), {min:-41, max:163});

// Zoom to an interesting location
Map.setCenter(71.2, 36, 9);

Image:

Some other examples

NLCD over hillshade, in northern New Mexico (using blend.multiply):

Elevation over slope, using blend.dodge (Grand Canyon):

License

The blend code is licensed under the terms of the MIT license.