By David Crowther
What is the best way to make a QGIS Layer Opaque?
Here we have two Layers in QGIS, the first is a Point Layer of Hospitals and the second is a Polygon Layer of Counties. The Counties Layer is 100% Opaque and therefore we cannot see through it.
If we swap the Layer Order and move the Hospital (Point) Layer to the bottom of the list, the Counties (Polygon) Layer which is 100% Opaque will make the Hospitals disappear.
One method to allow the Hospitals to be seen is to edit the Layer Properties of the Counties Layer and in the Symbology Tab choose Layer Rendering and make the Counties 50% Transparent.
Once Applied to the Counties Layer the Hospitals can now be seen even though they are ordered below the County Polygons.
This is fine, but can be a little time consuming to keep editing the Properties of the Layer.
Instead we can use a Widget and reveal an Opacity Slider tool for any Layer.
To do this, simply edit the Layer Properties for the Counties (Polygon) Layer and in the Legend tab we will choose to enable the Opacity Slider Widget.
This is done by simply highlighting the Widget in the Available Widgets list in the left pane and pressing the Right Arrow to move the Widget to the Used Widgets pane on the right.
Having pressed Apply and OK, you can see that the Counties Layer now has an Opacity Slider below the Layer where you can now edit the Opacity without having to enter the Layer Properties each time.
Simply slide the bar from left to right to adjust the Opacity of the Layer and make it Opaque or Transparent as required.