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1. Re: Editing Alpha Channel
Gyno-jiz May 22, 2009 2:01 PM (in response to G_Soucy)Control-click on the image layer in the layers panel, or bring up a selection of the layer transparency (or choose select > load selection > layer trans.). Then save that selection to a channel (select > save selection).
Now you can restore the opacity of pixels that aren't fully transparent using filter foundry, alphaworks, or just duplicating the layer, merging down, duplicating again, merging down five or six times.
Then load your saved selection and make it a layer mask by clicking the layer mask button in the layers panel (circle in rectangle).
Now you can paint using a black or white brush to affect the transparency values of the layer. Save as PNG when you're done. See here for more in depth coverage:
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2. Re: Editing Alpha Channel
Chris Cox May 22, 2009 3:34 PM (in response to G_Soucy)You can use layer masks or selections to increase transparency, but there is no good way to increase opacity (decrease transparency) or hand tweak values in the transparency channel.
Also, be careful of terminology -- PNG supports a single transparency channel. PNG does not support arbitrary alpha channels.
You seem to assume that an alpha channel is always transparency, when that is not the case (alpha channels can contain anything, transparency is a small subset of possible alpha channels - and some file formats specify that they support only transparency).
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3. Re: Editing Alpha Channel
Gyno-jiz May 22, 2009 3:39 PM (in response to Chris Cox)Chris Cox wrote:
You can use layer masks or selections to increase transparency, but there is no good way to increase opacity (decrease transparency) or hand tweak values in the transparency channel.
Maybe that should be a feature request. 110% opacity.
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4. Re: Editing Alpha Channel
Chris Cox May 22, 2009 3:41 PM (in response to Gyno-jiz)Actually, I'm just working on a feature to move the transparency channel to a place where it becomes editable.
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5. Re: Editing Alpha Channel
Semaphoric May 22, 2009 4:31 PM (in response to Chris Cox)Will it keep the original color value if set to zero? Or will it set the color to the background color of the layer, like it does now? I never understood the point of that.
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6. Re: Editing Alpha Channel
Christian Davideck May 23, 2009 4:22 AM (in response to Gyno-jiz)J Maloney wrote:
Chris Cox wrote:
You can use layer masks or selections to increase transparency, but there is no good way to increase opacity (decrease transparency) or hand tweak values in the transparency channel.
Maybe that should be a feature request.
support ++
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7. Re: Editing Alpha Channel
Chris Cox May 24, 2009 10:47 AM (in response to Semaphoric)"Will it keep the original color value if set to zero? Or will it set the color to the background color of the layer, like it does now? I never understood the point of that."
Huh? That makes zero sense.
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8. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 11:15 AM (in response to Chris Cox)Chris Cox wrote:
"Will it keep the original color value if set to zero? Or will it set the color to the background color of the layer, like it does now? I never understood the point of that."
Huh? That makes zero sense.
I am in no position to judge whether or not Semaphoric's observations are true or false, but in case they are indeed true, it's really not that difficult to understand Chris:Semaphoric wrote:
There is an important issue with a "Feature" of Photoshop's transparency: if, by any means, a pixel has been set to completely transparent (the value in its Alpha channel equal to zero), its original color value will be stripped out, and replaced with the current Background color, which will be seen when opacity is restored. -
9. Re: Editing Alpha Channel
Chris Cox May 24, 2009 11:20 AM (in response to Christian Davideck)Again, that doesn't make sense.
If you have zero opacity, the color channels have no meaning - no definition whatsoever (nothing there, no color values to speak of).
And Photoshop doesn't replace colors under zero opacity until you do some operation that needs color values out in the undefined region (like some filters that spread edge colors outwards from visible regions).
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10. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 11:30 AM (in response to Chris Cox)Chris Cox wrote:
Again, that doesn't make sense.
If you have zero opacity, the color channels have no meaning - no definition whatsoever (nothing there, no color values to speak of).
.... yes, you are right, it doesn't make any sense. BUT ... only until such time as
1) ... the user (by means of a plugin as PS doesn't support that natively very unfortunately) attempts to increase the opacity of a 0%-opacity-pixel ... hence our requests for an un-eraser-tool, that would do the reverse operation to the eraser tool (not decrease but increase a pixel's opacity) !
2) ... (see your own posting):
Chris Cox wrote:
... until you do some operation that needs color values out in the undefined region (like some filters that spread edge colors outwards from visible regions). -
11. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 11:34 AM (in response to Chris Cox)Chris Cox wrote:
Actually, I'm just working on a feature to move the transparency channel to a place where it becomes editable.
It's SOOOO wonderful to hear that, Chris!
I can imagine people jumping in the air, seeing this cool feature.
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12. Re: Editing Alpha Channel
Zeno Bokor May 24, 2009 11:35 AM (in response to Christian Davideck)wouldn't it be easier to just use Layer Masks for "un-erasing"?
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13. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 11:37 AM (in response to Christian Davideck)Christian Davideck wrote:
hence our requests for an un-eraser-tool, that would do the reverse operation to the eraser tool (not decrease but increase a pixel's opacity) !
... which now becomes unnecessary with your transparency-channel -editing-feature.
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14. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 11:43 AM (in response to Zeno Bokor)Zeno Bokor wrote:
wouldn't it be easier to just use Layer Masks for "un-erasing"?
Yes.
If you had one in the first place.
[Edit:] That's what J.Maloney meant in post #2 BTW.
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15. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 11:48 AM (in response to G_Soucy)G_Soucy,
you'll also find a lot of answers here: http://forums.adobe.com/message/1640834#1640834
For example the solidify filter.
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16. Re: Editing Alpha Channel
Reynolds (Mark) May 24, 2009 2:44 PM (in response to Christian Davideck)G_Soucy there is a workaround without plug ins - allowing you to increase your selected area to 100% Opacity. Just take your selected area and press command J multiple times. This will Stack duplicates of the area up in the layers panel. Then select all these duplicates and the original layer and press control E (merge) . Thats what Chris means when he says theres no good way at the moment, there isnt, but there are always work-throughs. An action could be made up which will effectively increase selected areas to 100%, without the use of plug-ins, in this way.
When you've got opacity to 100% you can then use layer masking to control EXACTLY how opaque the area is. At the moment transparency in Photoshop should always be controlled with masking, an extremely powerful method - looks like this may change in the future though.
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17. Re: Editing Alpha Channel
Semaphoric May 24, 2009 6:12 PM (in response to G_Soucy)This is what I base my observation on:
Running the Filter Factory, which can directly numerically manipulate the Transparency/Opacity channel, with a value of 1 in the 'A' (opacity) channel, and then running it with a value of 255 will yield the original image.
Running it with a value of zero, and then 255 yields the background color of the layer.
OK, with zero opacity the color value has no meaning. So why go the extra (meaningless) step of changing the values in the color channels? If those were left unchanged, we could then 'Un-erase'.
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18. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 6:28 PM (in response to Semaphoric)Semaphoric, did you write this FilterFactory plugin yourself ? Do you think you could you post it here in that case, or otherwise a web link ?
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19. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 6:33 PM (in response to Semaphoric)Semaphoric wrote:
Running it with a value of zero, and then 255 yields the background color of the layer.BTW, what do you mean with "background color of the layer" ? You're sure layers have a BG color? I thought there was only a currently selected foreground color and background color (which wouldn't be saved into your .psd document).
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20. Re: Editing Alpha Channel
Semaphoric May 24, 2009 7:07 PM (in response to Christian Davideck)The Filter Factory was an Adobe product that shipped with Photoshop until recently (at least until CS2, maybe CS3). It was never installed by default; it was an optional plugin found in the Goodies folder of the distribution disc.
You can find lots of filters created with it on the Web, but I don't know where you'd get th FF itself these days.
You are right about the background color. I was thinking of the Layer color, which is to make them distinctive in the Layers palette. So, just make that "yields the background color".
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21. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 7:12 PM (in response to Semaphoric)Actually I wasn't asking where to get FilterFactory from, but rather what's the name of the (FF-made) filter you are using and where could we get it from? Thanks.
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22. Re: Editing Alpha Channel
Christian Davideck May 24, 2009 7:14 PM (in response to Semaphoric)Semaphoric wrote:
This is what I base my observation on:
Running the Filter Factory, which can directly numerically manipulate the Transparency/Opacity channel, with a value of 1 in the 'A' (opacity) channel, and then running it with a value of 255 will yield the original image.
Running it with a value of zero, and then 255 yields the background color of the layer.
OK, with zero opacity the color value has no meaning. So why go the extra (meaningless) step of changing the values in the color channels? If those were left unchanged, we could then 'Un-erase'.
If you didn't write the filter yourself, than (I guess) you can't know if the color value of a 0%-opacity-pixel is REALLY gone, or if its just the way the plugin works (i.e.set 0% opacity pixels to 100% opacity and fill with currently selected BG color). It might have nothing to do with Photoshop itself.
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23. Re: Editing Alpha Channel
Semaphoric May 25, 2009 6:01 AM (in response to Christian Davideck)OK, I just ran a test.
Open new doc. Add a new layer, and fill it with some color. Hide the Background layer.
Mousing over the image shows the color in the Info panel. Use the FF to reduce the opacity to a value of 1, and the Info panel still shows the full value of the color. Use th FF to set the opacity to zero, and the Info panel shows nothing at all (blank) for the color value.
So I gather that what Chris was saying is that if the Opacity is zero, the color information is stripped out. Looking at it this way I can certainly see the point of it, as it would decrease the memory/storage space needed for the blank plixels - only one channel rather than four.
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24. Re: Editing Alpha Channel
G_Soucy May 25, 2009 6:03 AM (in response to Christian Davideck)Thank you all for the answers. As you can guess, I am not an expert with Photshop. However, I am 100% sure that Photoshop will erase colors in full transparency regions. I wrote a format plugin to support our own image format and that`s the first thing that I noticed (colors are gone when I tried to save them back) and I know that they were there to start with. This is a problem for us because we could decide (and we will often) to increase pixel opacity but it is not very good if the colors behind have been deleted. What the point of editing transparency if the colors behind have been changed? That would be the first thing to fix (since I consider that as a bug personnally).
As a beginner user of photoshop, I would have expected a simple transparency editor tool as mentionned in the discussion. Maybe my needs are different for the average user but I think that this would be a must for such a software. Later today I will experiment with the suggestions provided to increase pixel transparency but, at first glance, it does not sound simple.
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25. Re: Editing Alpha Channel
Christian Davideck May 25, 2009 7:39 AM (in response to Semaphoric)Semaphoric wrote:
So why go the extra (meaningless) step of changing the values in the color channels? If those were left unchanged, we could then 'Un-erase'.
G_Soucy wrote:
This is a problem for us because we could decide (and we will often) to increase pixel opacity but it is not very good if the colors behind have been deleted. What the point of editing transparency if the colors behind have been changed? That would be the first thing to fix (since I consider that as a bug personnally).
As a beginner user of photoshop, I would have expected a simple transparency editor tool as mentionned in the discussion. Maybe my needs are different for the average user but I think that this would be a must for such a software.
I fully support these suggestions.
See also:
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26. Re: Editing Alpha Channel
Semaphoric May 26, 2009 6:49 AM (in response to G_Soucy)Maybe you should re-write your format plugin to open the image with full opacity and a layer mask. Then, you could edit the mask all you like, and the color information would stay constant.
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27. Re: Editing Alpha Channel
Christian Davideck May 26, 2009 6:59 AM (in response to Semaphoric)Good idea. But there is still the issue that the plugin wouldn't know how to handle 0%-opacity-pixels, *in case* PS has REALLY stripped their color values.
And I still couldn't find the specific (FilterFactory made) filter you were talking about, in case you could tell me:
Christian Davideck wrote:
Actually I wasn't asking where to get FilterFactory from, but rather what's the name of the (FF-made) filter you are using and where could we get it from? Thanks.
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28. Re: Editing Alpha Channel
G_Soucy May 26, 2009 9:10 AM (in response to Semaphoric)Semaphoric wrote:
Maybe you should re-write your format plugin to open the image with full opacity and a layer mask. Then, you could edit the mask all you like, and the color information would stay constant.
Thank for the comment. I got the plugin to support both full opacity and regular transparent modes using a popup message for now to switch (transparent is the one for which I posted that message originally).
I found that in full opacity mode (loading the alpha channel as the 4th channel), I can do pretty much all the editing that I want. That works well with CS2 but not yet with CS4 (the CS4 SDK demo "simpleFormat"does not work either with CS4 so I posted a message in the SDK forum - the problem is that the 4th channel is not loaded in CS4 and also the image is loaded as a "Smart Object"). If you know anything about that issue, any help; is more then welcome...
Thanks!
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29. Re: Editing Alpha Channel
harry teasley May 26, 2009 9:34 AM (in response to Christian Davideck)I have asked many times, through many versions, for tools to manipulate opacity directly, instead of simply RGB. The painting tools and selection tools, specifically, would be greatly enhanced with opacity settings.
If I could use the magic wand to select all pixels of 4% opacity or less within a layer, it would be amazing. If I could use a paintbrush to paint 100% opacity into any pixel that has any data in it at all, that would be great.
The key to the request, to make it make sense to users, is that the opacity painting tools would have to ignore empty pixels, while the opacity selection tools would not: any pixel without data in it at all would not be painted into when painting opacity, but would be selected for the purposes of, say, selecting the least opaque pixels in a layer.
I have amazingly strong feelings about this: I do images where the bounding box of the data in a layer is important, and a stray pixel can mess things up. Or I've wanted to put a layer effect on a layer, but the plethora of nigh-invisible pixels with data in them cause the effect to be unusable. I have wanted to manipulate opacity directly long before now, without having to do an interim alpha-channel mockup. I've made this request for several versions now, and really hope to see something happen. My history-destroying "Opaquify" action could go away (the one that stamps dupes of a layer onto itself sixteen times). It would rock.
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30. Re: Editing Alpha Channel
Semaphoric May 27, 2009 7:49 PM (in response to harry teasley)To select all pixels with a less than 'n' opacity:
Select > Load Selection, using 'Layer x Transparency'.
Enter Quick Mask mode. Image > Adjustments > Threshold, with a value of n.
Invert, and exit Qick Mask.
To make all pixels that are not fully transparent become fuly opaque, paste the following into the A field of the Filter Factory and run it:
a == 0 ? 0 : 255
You can fake painting opacity by entering Quick Mask mode, painting the area you wish to opacify, exiting Quick Mask, and running the above filter.
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31. Re: Editing Alpha Channel
harry teasley May 27, 2009 8:01 PM (in response to Semaphoric)Semaphoric wrote:
To select all pixels with a less than 'n' opacity: <...>
I hope I didn't sound like I don't know the workarounds. It's just that they're terrible. Everything involves not dealing directly with the layer, but dealing with a mask/alpha representation of that layer. The extent to which I want to edit opacity is such that I want much more direct access: I want the magic wand to work on the actual layer, selecting opacity. If I don't like the selection, I want to ctrl-z, adjust the tolerance, and reselect, very quickly. I want an Edit > Fill > Contents Use Opacity option, to flood fill pixels containing data with opacity. I don't want to deal with intermediary representations, that's too removed, with too many steps. I do that now, when I have to: I don't want to.
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32. Re: Editing Alpha Channel
Christian Davideck May 27, 2009 8:25 PM (in response to harry teasley)harry teasley wrote:
I have asked many times, through many versions, for tools to manipulate opacity directly, instead of simply RGB. The painting tools and selection tools, specifically, would be greatly enhanced with opacity settings.
If I could use the magic wand to select all pixels of 4% opacity or less within a layer, it would be amazing. If I could use a paintbrush to paint 100% opacity into any pixel that has any data in it at all, that would be great.
[...] I've made this request for several versions now, and really hope to see something happen.support ++
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33. Re: Editing Alpha Channel
Christian Davideck May 27, 2009 9:08 PM (in response to Semaphoric)a == 0 ? 0 : 255
that's cool. thanks a lot for sharing.
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34. Re: Editing Alpha Channel
Christian Davideck May 27, 2009 9:16 PM (in response to G_Soucy)G_Soucy wrote:
As a beginner user of photoshop, I would have expected a simple transparency editor tool as mentionned in the discussion. Maybe my needs are different for the average user but I think that this would be a must for such a software.
I agree.
Semaphoric wrote:
if the Opacity is zero, the color information is stripped out. Looking at it this way I can certainly see the point of it, as it would decrease the memory/storage space needed for the blank plixels - only one channel rather than four.
Yes, buton the other hand, you've lost the color information forever and can't get it back with a (future) opacity tool or transparency channel editing (for example via FilterFactory).
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35. Re: Editing Alpha Channel
harry teasley May 27, 2009 9:22 PM (in response to Christian Davideck)Christian Davideck wrote:
Yes, buton the other hand, you've lost the color information forever and can't get it back with a (future) opacity tool or transparency channel editing (for example via FilterFactory).
You wouldn't want it back: with no way to know what was formerly there, it would result in unexpected behavior.
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36. Re: Editing Alpha Channel
Christian Davideck May 27, 2009 9:51 PM (in response to harry teasley)You wouldn't want it back: with no way to know what was formerly there, it would result in unexpected behavior.
I don't think so, but in case you aren't pleased with the results, you can always go back 1 step in history.





