3/21/2023 0 Comments Raster layer vs vector layerInputs all 65536 possible input values are pre-classified. Butįor non-8bit inputs more values need to be classified. Hundreds of thousands of pixels in a typical rendered image.įor simple 8bit inputs, only 256 input values need to be pre-classified. This is done because evaluating a pixel valueĪgainst a series of CLASS definitions is relatively expensive to do for the Works transparently but there are a few caveats and options to provideĬlassifying raster data in MapServer is accomplished by pre-classifying allĮxpected input values and using that table of classification results to lookupĮach pixel as it is rendered. That is input rasters with values outside the range 0-255. Classifying Non-8bit Rasters ¶Īs of MapServer 4.4 support has been added for classifying non-8bit raster That might have applied (such as 3 band RGB rendering). Single CLASS declaration in a raster layer will result in the raster layerīeing rendered using the one band classification rules instead of other rules In particular this means that including even a To the first band in the referenced file, but this can be altered with theīANDS PROCESSING directive. Raster classifications always take place on only one raster band. The other styling or control information is Only the COLOR, EXPRESSIONĪnd NAME parameters within a CLASS definition are utilized for If a CLASS has a NAMEĪttribute it may appear in a LEGEND. CLASS EXPRESSION ( >= 64 AND 200 AND > 200 AND > 200 ) STYLE COLOR 0 255 0 END END # Class using a regular expression to capture only pixel values ending in 1 CLASS EXPRESSION /* 1 / STYLE COLOR 0 0 255 END END ENDĪs usual, CLASS definitions are evaluated in order from first to LAYER NAME "JacksonvilleNC_CIB" DATA "Jacksonville.tif" TYPE RASTER STATUS ON CLASSITEM "" # class using simple string comparison, equivalent to ( = 0) CLASS EXPRESSION "0" STYLE COLOR 0 0 0 END END # class using an EXPRESSION using only.
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