[Qgis-user] Raster Calculator Expression to determine color

[Nick Papadonis]

HI Folks,

I’m trying to use the following expression to pick up the red colored routes on a map in which I used the info pointer tool to get the band values for the color. 

(“m at 1" < 238 AND “m at 1" > 213 AND “m at 2" < 123 AND “m at 2" > 98 AND “m at 3" < 125 AND “m at 3" < 99) * 1

Unfortunately, when this expression is used the resulting map is black with no other pixels for the detected color.

If I break down this expression to a simple “greater than” line for single band, then things work.

Does anyone know where this expression needs to be corrected?

Thanks again,
Nick