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Support non-linear colormaps

See original GitHub issue

A potentially handy feature (we have some data where it could be useful), would be to specify a non-linear color mapping for the data. To simplify the interface, it could be done as piecewise linear mappings, so essentially just passing several stretch ranges with an additional parameter specifying the colormap range. For example:

/z/y/x.png?stretch_ranges=[[0, 100, 5], [100, 200, 25], [200, 255, 226]]

would map raster values 0 too 100 to the first 5 colormap values, raster values 100 to 200 to the next 25 colormap values and raster values 200 to 255 to the remaining 226 colormap values.

Issue Analytics

State:
Created 5 years ago
Comments:10

Top GitHub Comments

2reactions

dionhaefnercommented, Jan 28, 2019

This is going to be possible with #128. If you do

/compute/{keys}/{z}/{x}/{y}.png?v1=B04&expression=log10(v1)&stretch_range=[0,5]&colormap=viridis

you’ll get the layer log-scaled in the interval (1, 100000). Corresponding colorbar:

/colorbar?stretch_range=[0,5]&colormap=viridis

1reaction

mrpgraaecommented, Jan 24, 2019

There is also the (minor) inconvenience of having to duplicate the data, if we need it for other things, such as the time-series / value extraction tool we have been talking about.