Raster Properties Dialog:Transparency Tab

Transparency Tab

QGIS has the ability to display each raster layer at varying transparency levels.<A NAME="84"></A> Use the transparency slider to indicate to what extent the underlying layers (if any) should be visible though the current raster layer. This is very useful, if you like to overlay more than one rasterlayer, e.g. a shaded relief-map overlayed by a classified rastermap. This will make the look of the map more three dimensional. <P> Additionally you can enter a rastervalue, which should be treated as NODATA. <P> An even more flexible way to customize the transparency can be done in the Custom transparency options section. The transparency of every pixel can be set in this tab. <P> As an example we want to set the water of our example rasterfile landcover.tif to a transparency of 20%. The following steps are neccessary:

1. Load the rasterfile landcover
2. Open the properties dialog by double-clicking on the rasterfile-name in the legend or by right-clicking and choosing Properties from the popup meun.
3. select the Transparency tab
4. <A NAME="enum:add"></A> Click the mActionNewAttributeAdd values manually button. A new row will appear in the pixel-list.
5. <A NAME="enum:transp"></A> enter the raster-value (we use 0 here) and adjust the transparency to 20%
6. press the Apply button and have a look at the map

<P> You can repeat the steps <A HREF="#enum:add">4</A> and <A HREF="#enum:transp">5</A> to adjust more values with custom transparency.

<P> As you can see this is quite easy to set custom transparency, but it can be quite a lot of work. Therefor you can use the button mActionFileSaveExport to file to save your transparency-list to a file. The button mActionAddRasterLayerImport from file loads your transparency-settings and applies them to the current rasterlayer.

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