2 Replies Latest reply on May 10, 2010 2:49 PM by DDurda

    Convert/encode grayscale value to opacity?

    DDurda

      Hi All,

       

      I am completely new to Fireworks, having worked for years in Photoshop. Sorry if I am asking about a simple/standard procedure, but it wasn't readily apparent to me in my first try in Fireworks.

       

      I am trying to create an image file for use in an astronomical visualization package called Celestia. To map clouds onto a planet I'd like to be able to take a grayscale image like this:

       

      http://celestia.h-schmidt.net/earth-vt/clouds1024.jpg

       

      and convert the darker portions to transparent, with the grayscale level scaling to differnt levels of opacity (white = opaque, black=transparent).

       

      Celestia can read .jpg and .png image files for surface texture maps and cloud maps. Is there any way to bring in a Photoshop .psd file with an image like this as an alpha channel and use the alpha channel info to save a single layer .png file with varying levels of opacity?

       

      Dan

        • 1. Re: Convert/encode grayscale value to opacity?
          Jim_Babbage Level 4

          Well, one way is to open the file in Fireworks and then from the filter menu choose Other > Convert to Alpha.

           

          Then set your canvas color  to transparent (in the Properties panel), and Export the file as a PNG 32. That should maintain the alpha transparency.

           

          Let me know if that works for you.

           

           

           

          Jim Babbage

          • 2. Re: Convert/encode grayscale value to opacity?
            DDurda Level 1

            Thanks Jim!

             

            This did indeed work to produce just the result I was looking for.

             

            One minor difference from what I was expecting: the Celestia files assumed that black would go to transparent and white would remain opaque. The "convert to alpha" within Fireworks takes white to transparent instead. But no problem - I just inverted the original image file first, ran the "convert to alpha" filter option, and then inverted the resulting image again within Fireworks before saving out as a .png file. Loaded into Celestia the resulting cloud image file worked just as I've been wanting.

             

            Thanks again - very helpful!

             

            Dan