JHV supports image overlaying for 8-bit raster images. A user can choose an image as the base layer and lay another image over bottom image. If the top image is not transparent, JHV also allows the user to make the image transparent. The user is also allowed to lay multiple images over the base image.
To start laying multiple images, you need to set the view option in the JHV window to layer. Clicking a folder with multiple 8-bit raster images brings up the Overlay window. The overlay window looks like,
The left side is the overlay panel for displaying overlay images. The right side is the control panel.
JHV provides options to choose the base layer and top layer image(s), make transparent images and specify opacity.
To make a transparent image, you select an image from the image list, click on the image to select the background color of that image, and then press the apply button. In the following example, the left side shows the image #2 with white background color is laid on image #0. Because image #2 is not transparent (with white background color), image #2 undercover image #0 and make image #0 not visible. The right side shows the same image layers but after making image #2 transparent.