Style: Invisible Pixels

We can assign transparent color, indicated with a diagonal hatch pattern in color wells, to pixels to make them disappear.    This topic uses the data set imported and initially styled in the Example: Import DDF SDTS DEM Raster File  topic.



Consider the illustration above, using a Fill choice of closest lower value , and a Bing satellite image server layer for background.  All pixels within a given height range are assigned the same color.



In the Style pane we see that all pixels between heights of 144 and 275 are assigned a light green color.



To remove background visual clutter, we will turn off the Bing satellite layer.   We will now make all of the green pixels disappear.



We do that by double-clicking into the small green color well for the 144 to 275 interval and choosing the transparent color choice.  Press Update Style.



The light green pixels disappear.   They are still in the image, but they have been made transparent so they are now invisible.



If we turn on the Bing satellite layer, we can see through the invisible pixels to that layer.  It is as if all pixels for heights between 144 and 275 no longer exist.



We can apply transparent color to show only those pixels of interest.   For example, in the Style pane above we have applied transparent color to all intervals except the 275 to 405 interval, which will be colored bright green.  



The result is a raster elevation image that appears to have pixels only in the height range from 275 to 405, with all pixels in that height range colored bright green.



We can turn on the Bing layer to see the resulting swath of pixels in context.



Using the Layers pane we can adjust opacity of the image layer to 50%, to enable the Bing layer below to be partially visible.


For an interesting visual effect, we can add hill shading.



In the Options tab we check the Use shading box, and enter 0.3 for the Z scale.   Press Update Style.



Seen without the Satellite layer, the green swath of pixels remains green, but is now modulated with hill shading to provide a 3 D effect.  It seems a bit light in color since the layer is seen with 50% opacity, so the white background partially shines through.




With the Bing satellite layer turned on, the combined effect of the hill shaded green raster and the photographic image appears.



The transparency of the layer allows some photographic imagery to show through.  We could reduce opacity further, to allow more of the satellite image to show through for a more enhanced combination effect.    


The square region of buildings to the left of the image above is the Lawrence Livermore National Laboratory, one of the two nuclear weapons design facilities in the United States, the other being in Los Alamos, New Mexico.


See Also



Images and Channels


Palette Images




Style: Drawings


Style: Images


Style: Labels


Style: Channels and Outputs Tutorial


Style: Autocontrast


Style: Contouring using Colors


Style: Hill Shading


Style: Palettes


Example: Create Two Images From One Table - More than one image can show data from the same table, including from the same tile field.


Example: Change the Contrast of an Image - In this example we use the Style pane to change the contrast of an image.


Example: Using the Assign Channels Button - The Assign Channels button in the Style pane for images allows us to assign channels to the standard three Red, Green, and Blue display outputs using frequently-desired arrangements.   The button provides a short cut way to assign all channels at once instead of doing each channel individually.


Example: Assign Channels - How to use the Style pane for images to assign channels to display outputs such as R, G, B or A.  This topic shows examples of channel combinations and the visual results.


Example: Set Image Transparency using Alpha - The A row in the Style pane allows us to specify what transparency we want to apply to the image, either by applying the same value for A for all pixels or by using one of the other channels to also control the A value.


Example: Autocontrast and Hill Shading Images using Style - This example shows how the Style pane can hill shade an image using the values of pixels as heights and generating shadows as if the Sun were located at the specified azimuth and altitude.   This capability is used most frequently with raster images to give an impression of three dimensionality in cases where the values of pixels represent terrain elevations.


Example: Style Applied to an Image Server Image - Because the Style pane simply changes the way an image is displayed and not the data, it can operate on read-only data served by various web servers such as WMS REST servers.    In this example we look at every detail of creating a data source using an image server and then manipulating the appearance of the display with Style.  We will connect to a WMS server that provides LiDAR data in various forms, including as terrain elevation.


Example: Import CTG Grid Cell File and Style - A companion topic to the Example: Import GIRAS vector LULC File and Style topic.  We import a CTG LULC Grid Cell file containing raster data showing land use and land cover and then we use Style to provide a more understandable display.


Example: Import DDF SDTS DEM Raster File -  We import a raster data terrain elevation surface from USGS SDTS format using DDF files.


Example: Import GIRAS vector LULC File and Style - A companion topic to the Example: Import CTG Grid Cell File and Style topic.   We import a USGS land use file in GIRAS vector format and then we use Style to provide a more understandable display.