Colors the given raster data with the color ramp.
The color ramp is applied horizontically between minval and maxval, i.e. a value of
minval in the raster is mapped to color of the upper left pixel while the value of
maxval is mapped to the color of pixel on the top right.
If the input raster data is of the data type byte, the color ray is deposited as a palette.
Otherwise a colored output file with RGB or RGBA channels is generated.