Creating a raster calculator

Now that we are familiar with some of the most useful canvas manipulation methods, let's take a look at a renderer that is independent of any image manipulation. There is a very useful source object in the library that can take multiple sources as input and create a new image based on the provided operations. In this example, called ch07_rastcalc, we will use the ol.source.Raster class to build a basic RasterCalculator function.

Raster 101

To understand the limitations of raster manipulation in OpenLayers 3 or, basically, any web mapping application, we should discuss how rasters work in GIS. If you are familiar with the concept, you can skip this part. If not, this section can give you some basic, but valuable, information, which can help you evaluate better architectural patterns.

First of all, every raster can be translated to a simple matrix. Rasters have a resolution and consist of uniform cells. Therefore, if we know the resolution of a raster, we can handle...