Learning the QGIS Python API - Building Mapping Applications with QGIS - page 69

• If the raster data has multiple bands, then typically, the bands would be combined
to generate the desired color. For example, one band might represent the red com-
ponent of the color, another band might represent the green component, and yet
another band might represent the blue component.
• Alternatively, a multiband raster data source might be drawn using a palette, or as
a grayscale or a pseudocolor image, by selecting a particular band to use for the
color calculation.

Let's take a closer look at how raster data can be drawn onto the map.

How raster data is displayed

The drawing style associated with the raster band controls how the raster data will be dis-
played. The following drawing styles are currently supported:

Drawing style Description

PalettedColor

For a single band raster data source, a palette maps each raster value to a color.

SingleBandGray

For a single band raster data source, the raster value is used directly as a grayscale value.

SingleBandPseudoColor

For a single band raster data source, the raster value is used to calculate a pseudocolor.

For a single band raster data source that has a palette, this drawing style tells QGIS to ignore
the palette and use the raster value directly as a grayscale value.

PalettedSingleBandGray

For a single band raster data source that has a palette, this drawing style tells QGIS to ignore
the palette and use the raster value to calculate a pseudocolor.

PalettedSingleBandPseudoColor

For multiband raster data sources, use a separate band for each of the red, green, and blue color
components. For this drawing style, the setRedBand() , setGreenBand() , and
setBlueBand() methods can be used to choose which band to use for each color compon-
ent.

MultiBandColor

For multiband raster data sources, choose a single band to use as the grayscale color value. For
this drawing style, use the setGrayBand() method to specify the band to use.

MultiBandSingleBandGray

MultiBandSingleBandPseudoColor For multiband raster data sources, choose a single band to use to calculate a pseudocolor. For
this drawing style, use the setGrayBand() method to specify the band to use.