Results 1 to 7 of 7

Thread: Editing Alpha in PhotoShop

  1. Default Editing Alpha in PhotoShop

    Here is a mini tutorial I posted in the Avsim painter's forum a couple years back. The particular thread has long since vanished for all but the most advanced users of the search function, and the images I originally posted in context with the tutorial have been reduced to hyperlinks. Since I put a moderate amount of effort into typing this up and editing the screenshots, and I still feel it may be of use to someone at some point, I'd like for it to once again see the light of day. Thanks

    *****


    I notice a lot of discussion about importing and exporting alpha channels in DXTBmp. There's really no need to do this if you're using PhotoShop to edit your textures. The alpha channel can be easily edited from within PhotoShop at the same time you're working with the main RGB channels. In fact I believe it's much easier to do it this way because you have the RGB channels to use as a guide when placing an alpha fill. This allows you to place your filled areas precicely where they need to be without guesswork or fiddling.

    I've done up a small tutorial here that shows my method of editing alpha channels. I'm using PhotoShop 7, but I'm sure the basic procedure is the same using any graphics editor capable of working with alpha channels.

    This is just a simple example I've created specifically for the purpose of explanation. I'm adding an alpha fill to the aluminum underbelly of this repaint to simulate polished aluminum in the sim. These are bits and pieces of a repaint I did for the iFDG A319 using the official iFDG paintkit.

    __________________________________________________

    Here I'm working on the right fwd part of the fuselage. So far I've copied two layers from my full-length master .psd; the base paintjob and the polished aluminum underbelly as a seperate layer. I've pasted them onto the "fuse.bmp" blank template that came in the paintkit, flipped them horizontally, and slid them into position over the template with the move tool.





    I've added the aluminum underbelly as a seperate layer rather than merging it with the base paintwork because I'm going to use it's selection to fill the alpha channel in the appropriate area. First I must create an alpha channel because this .bmp template doesn't have one (24 bit). This is done in the "channels pallette", if you don't see the channels pallette, you must enable it in the PS "Window" menu.





    When you create the alpha channel it will automatically be pure black so you must fill it. You can fill it with white, but in this case I'm going to use a very light gray (#F4F4F4) which will give my entire fuselage a bit of overall reflectivity. I set the foreground color to my desired shade of gray and then use "fill/foreground color" to fill the alpha channel.





    Next I want to darken up the alpha channel in the area underlying my aluminum underbelly, to add extra reflectivity and make it look like polished aluminum in the sim. I click on the RGB channel in the channels pallette, then return to the layers pallette and click on the "underbelly" layer to select it. Now I will load it's selection from the "Select" menu.

    (Alternatively you can simply click the "underbelly" layer in the layers pallette while holding down the CTRL key, but do explore the "Select > Load Selection" menu because there are a lot of possibilities for loading selections that aren't available through shortcut keystrokes such as "invert" or "intersect with selection")





    With the selection loaded I now switch back to the channels pallette and click on the alpha channel. Notice the underbelly area is still selected, all I need to do now is fill the area with a darker gray. This image shows the selected underbelly on the RGB, and the corresponding area on the alpha channel after filling it with gray:





    Doing it this way precisely places the alpha fill directly beneath the underbelly area on the finished texture .bmp. Attempting this with an exported alpha channel would obviously require either some guesswork or pasting the exported alpha channel onto the main .psd as a new layer in order to get the fill area positioned properly. The latter is pointless in my opinion when you're already using a graphics editor capable of working with alpha channels - you have the tools, use them.

    Now I'll repeat the process for the right-rear, left-front, and left-rear portions of the fuselage, and save this file as a .psd. This enables me to re-open it and modify the alpha, or add an alpha fill to another part of the texture later if desired.

    Once I'm ready to try out the texture in the sim, I simply re-open the .psd, flatten the image, and do a "Save as", saving it as a 32 bit .bmp with the appropriate filename for the particular model I'm working with. The .psd remains completely intact for future editing if desired.

    Finally I open the saved .bmp in DXTBmp for a final save to make it DX compatible. Notice that you can now see the newly created alpha channel in DXTBmp's alpha preview window. No need to export or import anything. I then save it as either "Extended 32 bit 888-8" or "DXT3" and fire up the sim to see how it looks. This final save for DX compatibility is really the only reason I have DXTBmp installed. Everything else gets done in PhotoShop.

    I hope that clears up some of the myths associated with importing and exporting alpha channels, and sheds some light on alpha editing in PhotoShop.

    Jim
    Last edited by Jim Robinson; 12-05-2009 at 09:06 PM.

  2. #2
    Join Date
    Oct 2009
    Location
    lost between how it is and how it ought to be
    Posts
    6,947

    Default

    Excellent job!!!

    Very well done.

    I use the same procedure except PS6 will not save 32bit bitmaps so I use targa as an alternative.

    Accomplishes the same thing.

    Thanks again Jim. Your efforts are appreciated.

    peace,
    the Bean

    [edit]
    I never understood why all tutorials say to flatten the image before "saving as". If I "save as" a format that doesn't support layers it gets flattened anyway. Am I missing something?
    [/edit]
    Last edited by StringBean; 12-05-2009 at 09:21 PM.
    WWOD---What Would Opa Do? Farewell, my freind (sp)

    Never argue with idiots.
    They drag you down to their level and beat you with experience

  3. Default

    Quote Originally Posted by StringBean View Post
    [edit]
    I never understood why all tutorials say to flatten the image before "saving as". If I "save as" a format that doesn't support layers it gets flattened anyway. Am I missing something?
    [/edit]
    In PS7 anyway it throws up a " File must be saved as a copy with this selection" warning and appends "copy" to the filename (i.e. "Alabeo172a_T.bmp" becomes "Alabeo172a_T copy.bmp") if you don't flatten it first. It still saves the .bmp just fine except that you have to backspace the "copy" out of the filename each time so I just started flattening them first to avoid the hassle. For screen shot editing and stuff where I use "Save for web" instead of "Save as" I never bother flattening it first.

    Thanks for the kind words Bean. Yeah maybe the detailed lead-in wasn't necessary, I "fluffed" it up a little .

    Jim

  4. #4
    Join Date
    Oct 2009
    Location
    lost between how it is and how it ought to be
    Posts
    6,947

    Default

    I don't get the warning in PS6, just a warning that "some data will be lost". I do get the "copy" added to the filename.

    Since I always save the PSD before copying or "saving as", I will try flattening the file next time as I have been in a hurry and forgot to delete the "copy" before. Then wondered why my changes don't show up in DXTBmp.

    I will see your "fluff" and raise you an atta-boy.

    peace,
    the Bean
    WWOD---What Would Opa Do? Farewell, my freind (sp)

    Never argue with idiots.
    They drag you down to their level and beat you with experience

  5. #5
    Join Date
    Jan 2007
    Location
    Hertford, Herts, UK
    Posts
    14,653
    Blog Entries
    1

    Thumbs up

    Thanks for the contribution Jim.

  6. #6

    Default

    Thanks Jim, really appreciate that one on the alpha!

    John Thuot II
    Team Lead/Founder/Texture Artist
    http://www.captainjohnfsx.net


    Checkout my new Facebook Page!
    https://www.facebook.com/pages/Airpl...05438883035386
    HP Z820 Workstation Intel Xeon 3.30ghz 8 Core Processor 2TB Hard Drive 16 gig of Ram 1125 Power Supply and 2 Gig Nvidia Geforce GTX 970. (YIPPPIE!!!!!)

  7. #7

    Default

    Well done Jim!

    It's always great to have resources available when we "forget"! I don't know about you, but I do that alot! I'll reference this page often!


    Thanks again!

Similar Threads

  1. Help! SBuilder for 2004 alpha channel/alpha map
    By ricardo_NY1 in forum Scenery Design
    Replies: 1
    Last Post: 06-19-2013, 06:10 PM
  2. Editing Alpha in PhotoShop question
    By jucano2 in forum Painter's Workshop
    Replies: 13
    Last Post: 04-11-2012, 11:51 PM
  3. Replies: 7
    Last Post: 04-22-2006, 02:00 AM
  4. ~~Alpha Alpha~~ Final Journey~~
    By EssexFireRescue in forum MSFS Screen Shot Forum
    Replies: 9
    Last Post: 04-14-2004, 11:58 AM
  5. Photoshop tutorial for editing templates?
    By Basil in forum DreamFleet General Discussion Forum
    Replies: 3
    Last Post: 01-11-2004, 11:29 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •