As Mango only accepts RGB raster images, we can’t automatically produce a legend for symbolized raster layers. The following work around allows you to add your own legend for the layer.
Step 1: Create an image for your symbolized raster
You can either use a screen capture tool to copy the legend from your desktop GIS or use a graphics package to design your own image. The image should be no wider than 285 pixels. Here is an example:
Step 2: Upload the legend image to an image hosting service
You can use any image hosting service to store the image such as PostImage. Once the image is uploaded click the “Direct Link – Copy to Clipboard” button.
Step 3: Add the image to the description of your layer
Go the the layer setting for your symbolized layer in Mango and go to the “General” tab. In the description paste the following code snippet:
<img src="DIRECT LINK GOES HERE" />
Replace the text between the double quotes with the direct link that you copied to your clipboard from PostImage. Your code snippet should now look similar to this:
<img src="http://s32.postimg.org/xwa5ukstx/Iy_W6x.gif" />
Now press save. Your legend image will now be visible in your maps legend.