36 Replies Latest reply on Nov 12, 2012 9:09 AM by Steve_Porter

    Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)

    Steve_Porter Level 1

      Greetings,

       

      I have a need to edit the channels independently (the values in my image mean things numerically rather than just what it looks like visually - so I need to edit the grayscale values in each of the R - G - B - and A channels seperately).

       

      I've searched through google and other forum posts and others bring up the concept of not understanding alpha versus transparency - but I have yet to see an explanation that fully explains what I'm experiencing.

      The closest was http://forums.adobe.com/message/2563436#2563436 But while I saw the exact same symptoms being described, the specific question was never really answered.

       

      Hopefully, a concrete example with pictures will be able to communicate the issue and solicit a useful explanation and/or solution.

       

      While, I'm specifically working with an RGBA image, below is a screenshot of a PNG that demonstrates the exact same behavior or symptom.  The screenshot below represents the PNG inside GIMP and PS CS4.  BTW, if you'd like to see or play with the image yourself, you can grab the same image at http://www.libpng.org/pub/png/img_png/imgcomp-440x330.png

      Alpha_treatment_in_GIMP_vs_PS.jpg

       

      GIMP, interestingly enough loads the PNG as expected - I see the transparency of the image treated as a true alpha channel.

      In PS CS4 however, the transparency seems to be somehow embedded in the Red - Green - and Blue channels; but NO seperate alpha channel.

      I can create the alpha channel through Select - Load Selection - Layer 0 Transparency - and pasting that into a newly created alpha channel - but the color channels still have the transparency mixture symptom - rather than showing the JUST the color component of that channel.  (Note the channel differences of the GIMP's Red Channel versus PS's Red Channel  - Said in another way, the yellow ball in the upper left of the image should have a red value of 255, so the Red Channels grayscale upper left ball should be white like it is in GIMP, rather than Gray as it is in PS).

       

      I never thought I'd experience GIMP being superior to Photoshop - so hopefully somebody can shed light on what is going on - what configuration I may have myself in - or a process to get the channels seperated out in the manner I wish to work with them.   Furthermore, maybe somebody can educate the Photoshop community what the difference between transparency and alpha[transparency] is.  I haven't found quite the right explanation that makes the light go off in my head yet.  As best as I have gleened "Alpha", which can be applied to any kind of channel, typically is in reference to transparency - and is applied as a document-whole transparency (as opposed to transparencies applied at a layer level - such as a layer mask).

        • 1. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
          conroy Level 5

          Open the PNG then do "Layer > Layer Mask > From Transparency" to make the image opaque with a layer mask causing transparency. Shift-click the mask thumbnail to disable it and make the image and its channels opaque.

           

          Screen-shot-2012-11-08-at-19.06.36.png

           

          You might find the SuperPNG plug-in useful: http://www.fnordware.com/superpng/

          .

          • 2. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
            Noel Carboni Level 8

            Long story short:  It's working properly, as designed.  Photoshop embraces the concept of transparency - it has for years.  As pointed out above, there are multiple ways to manage it (e.g., layer transparency or masks), though I think the Layer Mask from Transparency feature may have gone in in Photoshop CS5.

             

            Not to put too fine a point on it, but when Gimp and Photoshop differ, it's Gimp that's not performing up to "standard". 

             

            -Noel

            • 3. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
              Semaphoric Adobe Community Professional

              Transparency is in fact the Alpha, but is not directly editable as the other channels are. The way I've worked around this is to use the ancient Filter Factory plugin (32-bit only). Load and save the transparency selection, as you've done. Edit that and the color channels. Load the saved selection as an active one, and run the Filter Factory with 255 in the A field. This will replace the current transparency with your edited version. Now, save the file (you may want to delete the saved and edited alpha, since it has been copied into the transparency).

              • 4. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                Steve_Porter Level 1

                That is what I'd like to see, but unfortunately I don't seem to have the option of "Layer > Layer Mask > From Transparency" in Windows Photoshop CS4 .

                1 person found this helpful
                • 5. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                  Noel Carboni Level 8

                  Keep in mind that after the end of 2012 the discounted upgrade offer ends for all but Photoshop CS5 users.

                   

                  -Noel

                  • 6. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                    conroy Level 5

                    Then install the plug-in that I linked. It can give you RGB and Alpha channels as below.

                     

                    Screen-shot-2012-11-08-at-20.25.31.png

                    • 7. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                      Steve_Porter Level 1

                      conroy,  thanks for the help!  what subdirectory, if any, underneath  Plug-ins do I place this?  The unzip content (SuperPNG\Photoshop\32-bit) doesn't indicate where I actaully place the plugin (for example, something like a file format plugin like Targa.8BI would live in Plug-ins\File Formats).  Will this capability work for my RGBA files as well?

                      • 8. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                        conroy Level 5

                        Sorry, I use OS X and newer releases of Photoshop than CS4, so I can't safely advise where you should install the Windows plug-in. Someone reading this will help soon, I'm sure.

                        • 9. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                          Noel Carboni Level 8

                          Assuming the instructions say "copy it to your Plug-ins folder", then that's where it goes.

                           

                          Do you have a 64 bit OS?  If so, the folder for Photoshop 32 bit would be:

                           

                          C:\Program Files (x86)\Adobe\Adobe Phtotoshop CS4\Plug-ins

                           

                          I'd suggest making a subfolder, named for the plug-in.  It will help you keep things straight in the future, and you can put plug-ins in any number of subfolders under ...\Plug-ins.  Photoshop sorts out which ones are for opening/saving files, filtering documents, etc.

                           

                          -Noel

                          • 10. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                            Steve_Porter Level 1

                            Noel,

                             

                            Excellent - very useful information - I had always assumed the subdirectories where specific names and certain plugins needed to live.

                             

                            conroy, 

                             

                            I've placed the plugin as advised by Noel - but I still don't see an option for

                            "Layer > Layer Mask > From Transparency" in Windows Photoshop CS4 Extended - so I assume it is a capability that is no longer exists in CS4.

                             

                            ...bummer, I thought we were close.

                             

                            Does anyone have any suggestions then how to display the R - B - B - A  data then in  seperate channels in Photoshop CS4 (as it is presented in GIMP per the example above)?

                            • 11. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                              conroy Level 5

                              Did you restart Photoshop after installing the plug-in?

                               

                              The plug-in doesn't add a "From Transparency" command. It presents the following dialog when a PNG is opened.

                               

                              Screen shot 2012-11-08 at 21.12.42.png

                              • 12. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                Jeff Arola Adobe Community Professional

                                If you just want to recover the transparency so you can edit it, it's easy to do on a file like that in cs4.

                                There are several ways including a pixel bender plugin, but the easiest is to Ctrl click on the layer and save

                                the resulting selection to an alpha channel.

                                 

                                Then Select>Deselect and do Ctrl+J (layer via copy) and Ctrl+E (merge layers).

                                Repeat the above 8 more times, load the selection from the saved alpha channel and add a layer mask.

                                 

                                After the above steps:

                                 

                                cs3 1.png

                                 

                                Shift click on the layer mask to see the image without the mask

                                 

                                 

                                cs3 2.png

                                • 13. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                  Steve_Porter Level 1

                                  conroy,

                                   

                                  I've

                                   

                                  placed the plugin in:

                                  C:\Program Files (x86)\Adobe\Adobe Photoshop CS4\Plug-ins\SuperPNG

                                                SuperPNG.8bi

                                   

                                  Restarted - Making sure I was running the 32bit version - since there only appears to be a 32-bit plugin.

                                   

                                  Opened a png (the one in my example).

                                   

                                  ...but I never see the dialog you mention.

                                  • 14. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                    conroy Level 5

                                    Try going to "File > Open" and seeing if SuperPNG is showing up in the Format dropdown menu when a PNG is selected. I find the plug-in to be used by default for PNG when dragging files to Photoshop or opening via right-click in Finder when the plug-in is installed, but check in your "File> Open" dialog, anyway.

                                     

                                    Screen shot 2012-11-08 at 21.20.54.png

                                     

                                     

                                    When "Always bring up this dialog" is disabled in the plug-in interface shown in previous post, you need to use "File > Open" and hold down Shift when clicking Open button to get access to the plug-in's options.

                                    .

                                    • 15. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                      gener7 Adobe Community Professional & MVP

                                      Noel Carboni wrote:

                                       

                                      Not to put too fine a point on it, but when Gimp and Photoshop differ, it's Gimp that's not performing up to "standard". 

                                       

                                      -Noel

                                      Noel,

                                       

                                           I would be interested in a reference to the differences between Photoshop and Gimp. Is there document/link out there that would explain those differences and where Gimp does not perform up to standard?

                                       

                                      Gene

                                      • 16. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                        Steve_Porter Level 1

                                        conroy,  I'm am able to load the PNG per your instructions of manually opening up the .png with the SuperPNG format.  Now I'm trying to figure if it is better to get my .rgba's through to a png with the method. 

                                         

                                        R_Kelly's method almost worked - except the color layers still have transparency in them rather than being black in the absence of that color - and more importantly, I can't seem to edit the individual channels.  (and I'm a little concerned about the 8 copies that I merge - if they will retain the exact value the original image would have if it would come in like GIMP imports the image).

                                         

                                        My goal is to have each of the channels R - G  - B - A  all be editable grayscale channels - I need to have it come in exactly because the values actually mean information (rather than just visual imagery).  ...basically how GIMP treats channels; but obviously I want to use Photoshop.

                                        • 17. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                          Jeff Arola Adobe Community Professional

                                          All the black means is the transparency in the case of your image.

                                          If your were to load the image as conroy has you would need to Crl click on the alpha channel to get your selection and then add a layer mask so you can see the image as it looks in gimp.

                                           

                                           

                                          In the method i posted, the image should look just like it does in gimp and you should be able to edit the transparency or edit the individual channels.

                                          Gimp just shows the alpha channel (transparency) where as newer versions of photoshop do not, but the alpha channel (transparency channel) is still there in photoshop

                                          as Semaphoric explained in post #3.

                                          • 18. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                            Noel Carboni Level 8

                                            Hi Gene,

                                             

                                            I am not a Gimp expert nor do I know of much in the way of documentation, BUT, what I was getting at is that one does not normally expect to see the leading professional graphics software measured to the standard of freeware.  The "thing" that most would expect to compare to in common language would be that which is considered the leader.

                                             

                                            Ask yourself:  When people mean to ask "Has that image been manipulated digitally?", do they say (in slang), "Has that been Photoshopped?" or do they say "Has that been Gimped?"

                                             

                                            Whether Gimp actually might work better is an entirely different conversation, and one I'm just not qualified to have.

                                             

                                            -Noel

                                            • 19. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                              conroy Level 5

                                              Steve_Porter wrote:

                                               

                                              My goal is to have each of the channels R - G  - B - A  all be editable grayscale channels - I need to have it come in exactly because the values actually mean information (rather than just visual imagery).  ...basically how GIMP treats channels; but obviously I want to use Photoshop.

                                               

                                              I thought the SuperPNG plug-in does correctly provide R,G,B and A (when the option to multiply by alpha is not enabled) from the PNG file. Do you suspect errors?

                                              • 20. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                Steve_Porter Level 1

                                                R_Kelly, 

                                                 

                                                (and I must thank you and everybody for their patience in this thread!)

                                                 

                                                In my specific case the black in any of the four seperate channels actually means something - it means a value of 0.

                                                 

                                                Visually, the following two would be result in the same exact image...

                                                transparency in the Red [grayscale] channel       -   combined with transparency from the alpha channel

                                                full black in the Red [grayscale] channel            -   combined with transparency from the alpha channel.

                                                 

                                                However in my specific case they do not; AND I need to be able to edit the values in each of the 4 seperate channels.

                                                 

                                                BTW, It appeared as it the Filter Factor  that Semaphoric mentioned (I assume the "Transparency" ones where what I needed) were "Currently Down!!!" so I was unable to attempt that path.

                                                http://thepluginsite.com/resources/freeff.htm

                                                • 22. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                  conroy Level 5

                                                  R_Kelly wrote:

                                                   

                                                  If your were to load the image as conroy has you would need to Crl click on the alpha channel to get your selection and then add a layer mask so you can see the image as it looks in gimp.

                                                   

                                                   

                                                  The way I showed the PNG loaded as opaque grayscale R,G,B and Alpha channels is what Steve seems to require. Adding a mask as you suggest would make the R,G and B channels become semi-transparent.

                                                  • 23. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                    Noel Carboni Level 8

                                                    Seems like a lot of wheel-spinning to avoid having to upgrade to Photoshop CS6, with the Layer Mask From Transparency option.  The combined time people have put into writing here exceeds the $200 upgrade price, almost no doubt. 

                                                     

                                                    -Noel

                                                    • 24. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                      Steve_Porter Level 1

                                                      I think I've finally determined that modern Photoshops have gone in a different direction that I feel "Alpha" should be done.

                                                      (good or bad).

                                                      Here are the steps and/or details of how I arrived at that conclusion.

                                                      If nothing else this has been very educational on how Photoshop treats alpha.

                                                       

                                                      - Import your alpha'd PNG with SuperPNG format (see above on how to make sure you use the SuperPNG plugin to load the .png).
                                                      - In the SuperPNG dialog select "Alpha appears as seperate channel"
                                                      - Create a layer from the Background and Delete the original Background
                                                        (since the Background is locked and we can't edit the Background - we want to add a layer mask based on the alpha)
                                                      - Ctrl-Left Select the "Alpha 1" channel - Ctrl-C - and hit the "Add Layer Mask" button (square with the circle at the bottom of the LAYERS rollout)
                                                      - For this demo and clarity, I went ahead and deleted the alpha "Alpha 1" that came in through the SuperPNG plugin

                                                       

                                                      So now I have the Layers like I kindof expected the main document to just come in as (kindof though - it is presented in a Layer Mask rather than Alpha Channel).
                                                      What is interesting - which you'll see if you toggle the layer mask on and off
                                                      (shift-click the mask thumbnail in the layer)
                                                      Note how the thumbnails in the channel views render differently during the toggle.
                                                      When the mask is off you see the individual color channels like I expect - black where there is an absence of that color.
                                                      However when you enable the layer mask - the individual color channels show in semi-transparent/checkerboard.

                                                      DisabledLayerMask.jpg

                                                      EnabledLayerMask.jpg

                                                       

                                                      So this is exactly how the color channels are presented when loading in a .png (WITHOUT the SuperPNG plugin) or an .rgba
                                                      ..you get the semitransparent views of the color channels - BUT the difference is - you have no way to directly see or edit the Alpha channel.
                                                      nor are the color channels represented as completely opaque versions.
                                                      What is really interesting - it is there though - if you Ctrl-Left Select the layer, Ctrl-C, and "Add Channel Mask" - you'll get the Alpha mask.
                                                      HOWEVER, the big issue is that you can't toggle or edit the Color-Channels like the Layer counterpart above;
                                                      they are ALWAYS the semitransparent/checkboard version;  AND now we basically are double applying transparency
                                                        (due to the still embedded alpha/transparency AND the newly create "Alpha 1" channel)

                                                       

                                                      PNGWithoutSuperPNG.jpg

                                                       

                                                      I think this a bug (or a poor reimplementation of modern Photoshop releases; I believe older Photoshops used to break out Alpha in the "arguably correct" way - and in fact the way GIMP currently does).
                                                      Or maybe there are other explanations - like abstracting some of this complexity away from less advance users, etc?

                                                      So the SuperPNG plugin was useful in experimenting, understanding, and demonstrating what is going on.
                                                      However, if I'm trying to read in .rgba directly, I don't think I have a way of making the "Alpha appear as a seperate channel" as I think any image with "alpha" component should.
                                                      (png, tiff, rgba, etc).

                                                      • 25. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                        Steve_Porter Level 1

                                                        Noel,

                                                         

                                                        will the "Layer Mask From Transparency option" keep place the color channels in their "opaque" state like I require? 

                                                        ...if so, you are correct about the cost/benefit.   Or I could use GIMP for free!    (I couldn't help myself Noel!)

                                                          ...but seriously I really wanted to figure out a way to stay in Photoshop to benefit from the other features where it clearly is a winner.  I am just amazed that it seemingly doesn't have a way to treat incoming files with alpha in what I consider the "correct" way - or at the very least have someway of getting it easily into that form - color and alpha channels in grayscale form that I can edit independently.

                                                         

                                                        I learned alot (and I hope other people benefited as well) from the journey!  ...Thanks everybody!

                                                         

                                                        I'd love to see if anybody has a brilliant or clever solution - but I agree with Noel - probably enough wheel-spinning on this one.

                                                        • 26. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                          conroy Level 5

                                                          Steve_Porter wrote:

                                                           

                                                          What is interesting - which you'll see if you toggle the layer mask on and off

                                                          (shift-click the mask thumbnail in the layer)
                                                          Note how the thumbnails in the channel views render differently during the toggle.
                                                          When the mask is off you see the individual color channels like I expect - black where there is an absence of that color.
                                                          However when you enable the layer mask - the individual color channels show in semi-transparent/checkerboard.

                                                           

                                                           

                                                          Yes, that's what I wrote to R_Kelly, earlier, because I thought you specifically didn't want semi-transparent channels.

                                                           

                                                           

                                                          HOWEVER, the big issue is that you can't toggle or edit the Color-Channels like the Layer counterpart above;

                                                           

                                                          I don't understand. If a layer is targeted then you can display and edit each of the R, G and B channels as a grayscale image.

                                                           

                                                           

                                                           

                                                          So the SuperPNG plugin was useful in experimenting, understanding, and demonstrating what is going on.

                                                          However, if I'm trying to read in .rgba directly, I don't think I have a way of making the "Alpha appear as a seperate channel" as I think any image with "alpha" component should.
                                                          (png, tiff, rgba, etc).

                                                           

                                                          Again, I don't understand. As far as I see, the SuperPNG plug-in set to create separate Alpha channel and not multiply it into the RGB does give you straight R,G,B and a separate Alpha channel. Here again is the screenshot of the necessary settings. Maybe I've misunderstood your requirements from the beginning, though.

                                                           

                                                          Screen+shot+2012-11-08+at+21.12.42.png

                                                           

                                                           

                                                           

                                                           

                                                           

                                                           

                                                           

                                                          .

                                                          • 27. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                            conroy Level 5

                                                            Steve_Porter wrote:

                                                             

                                                            Noel,

                                                             

                                                            will the "Layer Mask From Transparency option" keep place the color channels in their "opaque" state like I require? 

                                                             

                                                             

                                                            Yes, you saw it in my first screenshot in the thread!

                                                            • 28. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                              Noel Carboni Level 8

                                                              I guess I just don't see a problem manipulating R, G, B, and a layer mask.

                                                               

                                                              The Layer Mask is available in the Channels panel if you want to manipulate it directly, and you can view the RGB with or without the transparency just by shift-clicking on the layer mask to disable/enable it.

                                                               

                                                              Seems like everything that's needed to me.  Did I miss something?

                                                               

                                                              Transparent1.png

                                                               

                                                              Transparent2.png

                                                               

                                                              Transparent3.png

                                                               

                                                               

                                                              -Noel

                                                              • 29. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                                Steve_Porter Level 1

                                                                conroy,

                                                                 

                                                                So you are on CS6?

                                                                 

                                                                So some of the confusion in the prior posts - I ultimately will be needing to do these types of things in .rgba  -  I just used PNG as a shareable example (unfortunately I can't directly share what I'm doing).

                                                                 

                                                                The above examples that I confused you with, was to demonstrate what I gleaned from your SuperPNG capability that is is going on with the channels without the SuperPNG plugin (or in my case, if I needed to load .rgba).  You were correct, I specifically wanted the opaque versions - I went through all that trouble (and confusion evidently) to demonstrate what I think I figured out what was going on.  Thanks for sharing the SuperPNG, I think it was key to see what I suspect is going on in CS4 of Photoshop - but I missed the the "Layer Mask From Transparency" was a CS6 capability.

                                                                 

                                                                So the comments about not being able to edit in the RGB are when you DON'T use SuperPNG (or in my case try to load an .rgba) - I obviously didn't make it clear enough the compare and contrast of the point I was trying to make - there was a certain flowof the example (and it is getting complicated!);  apologies.

                                                                 

                                                                conroy and Noel especially, thanks for sticking in there with me!

                                                                • 30. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                                  Steve_Porter Level 1

                                                                  Noel Carboni wrote:

                                                                   

                                                                   

                                                                  Seems like everything that's needed to me.  Did I miss something?

                                                                   

                                                                  The issue is, if I'm trying to read an .rgba (which Photoshop is seeming to have an issue with) I don't have the benefit of a feature that can load "Alpha appear as a seperate channel" with just ANY format - only PNGs using the SuperPNG plugin.

                                                                   

                                                                  Futhermore, if I manually construct a image in Photoshop using the layer mask approach, I STILL have an additional step of moving the layer mask back out to [alpha] channel so that I can write out into .rgba properly (no format that supports transparency like.rgba or tiff,  will give you the  Save Option of "Alpha Channels"  unless the transparency is correctly placed in a true "Alpha" channel - as opposed to a Layer Mask).

                                                                   

                                                                  BTW, I have a different issue now where Photoshop CS4 won't even read my .rgba's - It seemingly writes them correctly -  once you move the transparency layer mask out to an Alpha Channel and save with PhotoShop -  I can read an .rgba with GIMP just fine.  but if I try to read this very same file into PhotoShop - Photoshop CS4 gives me a "Could not complete your request because of a program error."  Does anybody know if there is potentially a newer version of the SGI .rgba plugin than what I'm using (or some configuration I need to be aware of)?

                                                                   

                                                                  So in summary - I didn't think the format would matter for the capability I was trying to ask (unfortunately, since there was a path with SuperPNG that led us down a road that was not available to the true format that I was ultimately going to deal with - apologies - my intent was to find an example the simply demonstrated the way CS4 dealt with alpha - which I still argue isn't as flexible as it should be). I think it was still useful to have the SuperPNG to help figure out what was going on.

                                                                   

                                                                  Looks like I just need to upgrade to CS6; but unfortunately, there are still some manual steps to move around the layer mask to a true channel alpha mask just before writing.  (and potentially a bigger issue with the .rgba reader plugin).

                                                                   

                                                                  I was just surprised I have to do this much wrangling with Photoshop.

                                                                  • 31. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                                    Jeff Arola Adobe Community Professional

                                                                    If your interested in a plugin that mimicks the layer mask from transparency in cs5/cs6 you could install the pixel bender plugin

                                                                    for photoshop cs4 and then use the removeTransparency.pbk (pixel bender kernal file).

                                                                    It also works on files other than pngs.

                                                                     

                                                                    The only steps you have to do is load, save the selection and add the layer mask (if want the layer mask part, which could be recorded in an action).

                                                                     

                                                                    Pixel bender from adobe labs:

                                                                    (you have to click where it says pixel bender for cs4 then look on the next page for archived downloads)

                                                                     

                                                                    http://labs.adobe.com/technologies/pixelbenderplugin/

                                                                     

                                                                     

                                                                    removeTransparency.pbk

                                                                    (right click on the page and Save As)

                                                                     

                                                                    http://neo.cycovery.com/removeTransparency.pbk

                                                                     

                                                                     

                                                                    Example action and the result:

                                                                     

                                                                    Untitled-25.png

                                                                     

                                                                    After shift clicking on the layer mask:

                                                                     

                                                                     

                                                                    Untitled-44.png

                                                                     

                                                                    pixel bender plugin:

                                                                     

                                                                    pb 3.png

                                                                     

                                                                     

                                                                    If you want to install the plugin and need directions in addition to those at adobe labs, we can provide help.

                                                                    • 32. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                                      Noel Carboni Level 8

                                                                      Steve_Porter wrote:

                                                                       

                                                                       

                                                                      The issue is, if I'm trying to read an .rgba (which Photoshop is seeming to have an issue with) I don't have the benefit of a feature that can load "Alpha appear as a seperate channel" with just ANY format - only PNGs using the SuperPNG plugin.

                                                                       

                                                                      Looks like I just need to upgrade to CS6; but unfortunately, there are still some manual steps to move around the layer mask to a true channel alpha mask just before writing.  (and potentially a bigger issue with the .rgba reader plugin).

                                                                       

                                                                      As you have surmised, you need a Photoshop that has the Layer Mask from Transparency function (or the Pixel Bender plug-in R_Kelly mentioned).

                                                                       

                                                                      What additional steps do you need?  I'm not getting that.  Just save the partially transparent file and Photoshop will put all the channels in the right place to make it partially transparent.

                                                                       

                                                                      You seem to keep wanting to make this more complex than it is.

                                                                       

                                                                      -Noel

                                                                      • 33. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                                        Jeff Arola Adobe Community Professional

                                                                        Yes, i'm confused too.

                                                                         

                                                                        Do you need the file for another application, besides gimp, that doen't read the transparency channel correctly?

                                                                        • 34. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                                          Level 7

                                                                          Send me a copy of some .rgba files that fail to read.

                                                                           

                                                                          I don't think the SGI format plugin has been changed in a long time, but there's always compiler changes and obscure bugs yet to be found...

                                                                          • 35. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                                            conroy Level 5

                                                                            Steve_Porter wrote:

                                                                             

                                                                            The issue is, if I'm trying to read an .rgba (which Photoshop is seeming to have an issue with) I don't have the benefit of a feature that can load "Alpha appear as a seperate channel" with just ANY format - only PNGs using the SuperPNG plugin.

                                                                             

                                                                            If Photoshop won't open your SGI RGBA, try XnConvert.

                                                                             

                                                                            Maybe this solution will work with CS4, but I don't have CS4 to test it.

                                                                             

                                                                            When Photoshop CS6 does read a SGI RGBA (optional plug-in download), it creates transparency from the alpha, like it does with PNG.

                                                                             

                                                                            Use XnConvert to convert SGI RGBA to TIFF with alpha. CS6 will open the TIFF and keep the alpha channel separate, like SuperPNG can do with PNG.

                                                                             

                                                                            Or use XnConvert to convert SGI RGBA to PNG then use SuperPNG to open the PNG and keep the alpha channel separate.

                                                                             

                                                                             

                                                                            XnConvert: http://www.xnconvert.com/

                                                                            • 36. Re: Photoshop not presenting alpha channel as expected (like I'm seeing GIMP does)
                                                                              Steve_Porter Level 1

                                                                              Thanks everybody for your patience and professionalism (sometimes forum post derail really quickly - this one went longer than I had expected).

                                                                               

                                                                              When I tried a different SGI format plugin from:  http://telegraphics.com.au/sw/product/SGIFormat  it came in like I expected (the alpha channel from the .rgba went directly into a seperate transparency alpha channel as opposed to directly (or "Alpha makes layer transparent") on the R-G-B channels).

                                                                              ...but I learned alot (and hopefully others benefitted as well) how the alpha/transparency works in Photoshop - and when I need to work with PNGs in the future (which I do on occasion) - the SuperPNG plugin is a great tool to make that choice.

                                                                               

                                                                              As a side note, I wonder if it would be possible to have an advanced load option on all formats that support transparency to make this choice (not sure where in the chain, and how Photoshop works under the covers, if this is even possible or worth it).

                                                                              ie. something like PNG (as all other formats that support transparency) would use this proposed native Photoshop capability rather than needing to get SuperPNG - and obviously all other formats would benefit/work this way.

                                                                               

                                                                              Thanks again for everyone getting me through my issue!

                                                                               

                                                                              -cheers,

                                                                              Steve