The discussion in this chapter uses the sample file
samples/layers8bit.hdf
located in the JHV installation directory.
8-bit Raster Image
in the file
samples/layers8bit.hdf
. The image overlay window will appear,
with the overlay panel on the left and a control panel on the right.
JHV provides options to choose the base layer and top layer image(s), to render a selected background color transparent, and to adjust image opacity.
8-bit Raster Image
folder in layers8bit.hdf
)
overlaid on a United States map (image #0 in the same folder and file).
To make an image transparent, select the image from the image list and click on the image to select the background color to be rendered transparent; the selected background color will appear in the Background panel. Upon pressing the Apply button, the selected background will become transparent and lower images in the stack will become visible.
In Figure 8.2, the left side illsutrates the high and low air pressure map (image #2) with white background overlaid on the United States map (image #0). Since the pressure map's white background has not yet been made transparent, it still obscures the U.S. map. The right side of the figure illustrates the same image layers, but after rendering the pressure map's white background transparent.
Slide the opacity slidebar, labeled Opaque in the image overlay window control panel, and press Apply to change the opacity of an image. You can repeat the process to fine-tune the opacity. An image layer with 0% opacity is completely transparent, while a layer with 100% opacity is completely opaque. Opacity can be set independently for each layer.
Figure 8.3 illustrates a cloud cover image (image #4 in the above folder and file) overlaid on the U.S. map (image #0) with 50% opacity.