I have encoded some metrics in a 4-band geotiff that will be served by MapServer (v7.4), and I want to "decode" them client-side for display using raster operations in OpenLayers (v6.1). (This is something somewhat similar to what is done in this openlayers workshop.)
The problem is that my metrics values range from 1 to 156 (and I used 255 for nodata), and MapServer scale them to 0-254 during rendering for better display, so the client do not have access to the original metrics.
I would need the client to have access to the original values. I have tried adding the following directives to the mapfile layer definition, but to no avail. 'PROCESSING "LUT=1:1,156:156"' or 'PROCESSING "SCALE=0,254"'
Here is the layer definition:
LAYER NAME tif_source STATUS ON TYPE RASTER DATA "/test.tif" PROJECTION "init=epsg:32198" END METADATA wms_enable_request "*" wms_title "tif_source" END # PROCESSING "SCALE_1=0,254" ## does not produce the expected result # PROCESSING "LUT=1:1,156:156" ## does not work either PROCESSING "LOAD_FULL_RES_IMAGE=YES" DEBUG 4 END
How should I prevent MapServer from scaling the raster values during rendering?