[Gimp-developer] Enhancement request - Use alpha channel for non-transparent information
Okay I made a feature request at http://bugzilla.gnome.org/show_bug.cgi?id=543810 but it's missing a solution that will not remove any functionality. Martin mentioned something about supporting auxiliary channels in RGB mode and I'm not sure what that means so if anyone could help me out on that or give advise on how this could work. Also http://bugzilla.gnome.org/show_bug.cgi?id=486902 was referenced and again, I don't see how that relates to my feature request but I am open to hear from anyone willing to explain. A copy of the request is below. When I use GIMP I sometimes use the alpha channel for things like bump maps, specular maps or even parallax maps and would be good if there was a check box when you right-click the alpha layer that would enable/disable it's use for transparency. This could have the same effect as using the threshold alpha with a setting of 0 while it's disabled. Another way to do it could be if you make the alpha channel invisible it would look like the threshold alpha mentioned above and when only the alpha channel is selected then you could edit and apply effects to the alpha channel as if it were a custom channel. This could apply with all channels but I believe the alpha channel needs this the most. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Enhancement request - Use alpha channel for non-transparent information
On Sun, 20 Jul 2008 21:22:11 +1000, Snake Arsenic [EMAIL PROTECTED] wrote: Okay I made a feature request at http://bugzilla.gnome.org/show_bug.cgi?id=543810 but it's missing a solution that will not remove any functionality. [...] I think that it would be a big mistake to use the alpha channel for anything else than transparency. I assume that you are asking for this because you have some program (I don't know which one) that is incorrectly using the alpha channel to store bump map information or something else that is not related to transparency. It is likely that this program doesn't use a file format that supports layers or independent channels, so its authors of have decided to hijack the alpha channel in some existing file format. The correct way to solve this problem is to use layers instead of abusing the alpha channel (or maybe additional channels, but I think that using layers would be more convenient in this case). With layers, it is very easy to toggle the visibility of the image or the bump map layer, specular map layer or whatever else you are working on. So instead of extending the mistakes done by the authors of some other software, it would be much better to know what file format has been subverted, and to perform the conversion in the file plug-in: * When the plug-in loads a file that uses this strange format, it would convert the alpha channel into a layer and mark that layer (using a special name like the GIF plug-in does for animations, because that can be edited easily by the user if necessary). * You would then be free to edit the image in GIMP and modify the layer containing what should be visible or the layer containing the bump map. * When saving the file, the plug-in would detect that some layers have a special name and would then combine these layers in a way that can be read by whatever other program you are using. So I suggest that you: 1) Identify what file formats need some special treatment. 2) Check if there is a way to detect what files using that format are special, so that we do not have to ask the user every time if a file using that file format should be read in the intended way (alpha channel = transparency) or in the non-standard way (bump map). 3) Suggest improvements to the corresponding file plug-ins, instead of requesting major changes in the GIMP core. -Raphaël ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Enhancement request - Use alpha channel for non-transparent information
On Sunday 20 July 2008, Raphaël Quinet wrote: On Sun, 20 Jul 2008 21:22:11 +1000, Snake Arsenic [EMAIL PROTECTED] wrote: Okay I made a feature request at http://bugzilla.gnome.org/show_bug.cgi?id=543810 but it's missing a solution that will not remove any functionality. [...] Hi! Going beyond all of Raphael's excelent remarks, I still see some issues here : 1) The ability to ciew teh layer sans transparency and edit the alpha channel as if it where any other channel is provided in GIMP - you copy the alpha channel to the layer's mask, and edit it (the layer's mask). 2) The request indeed points a thing: GIMP _has_ the ability to set each channel visible or not - in the layers channel. If the image channel is disabled in the channels dialog, channel cvaleus are considere as zero for all display operations. However, setting the alpha channel to zero in this way - which is what gimp does -is useless - you just can't see anything in the image, as it is rendered with alpha = 0 for all layers. I'd suggest that when the alpha channekll si disabled in the channel dialog, image is rendered with alpha =1.0 (255) insetead. That would: a) enable the feature thought when the ability to run channel'son and off was included; b) Make gimp attend the requesterś (Snake) needs. Maybe the bug request should be chanegd accordingly? Moreover - I really think it is a more usefull (even if seldom used) behavior for disabling the alpha. What do you say of doing it? I think that it would be a big mistake to use the alpha channel for anything else than transparency. I assume that you are asking for this because you have some program (I don't know which one) that is incorrectly using the alpha channel to store bump map information or something else that is not related to transparency. It is likely that this program doesn't use a file format that supports layers or independent channels, so its authors of have decided to hijack the alpha channel in some existing file format. The correct way to solve this problem is to use layers instead of abusing the alpha channel (or maybe additional channels, but I think that using layers would be more convenient in this case). With layers, it is very easy to toggle the visibility of the image or the bump map layer, specular map layer or whatever else you are working on. So instead of extending the mistakes done by the authors of some other software, it would be much better to know what file format has been subverted, and to perform the conversion in the file plug-in: * When the plug-in loads a file that uses this strange format, it would convert the alpha channel into a layer and mark that layer (using a special name like the GIF plug-in does for animations, because that can be edited easily by the user if necessary). * You would then be free to edit the image in GIMP and modify the layer containing what should be visible or the layer containing the bump map. * When saving the file, the plug-in would detect that some layers have a special name and would then combine these layers in a way that can be read by whatever other program you are using. So I suggest that you: 1) Identify what file formats need some special treatment. 2) Check if there is a way to detect what files using that format are special, so that we do not have to ask the user every time if a file using that file format should be read in the intended way (alpha channel = transparency) or in the non-standard way (bump map). 3) Suggest improvements to the corresponding file plug-ins, instead of requesting major changes in the GIMP core. -Raphaël ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Enhancement request - Use alpha channel for non-transparent information
That sounds really good Joao, I was thinking of a use layer as alpha overriding option for the TGA save dialog(which eliminates the layer being used in the final image other than to serve as the alpha channel, of course). I'm also thinking of an extract alpha to layer option in a menu such as transparency or as a filter that also performs the function of setting the alpha channel to 1.0 in all pixels of that layer. This could provide easy editing of multiple layers with individual masks/alpha as the combined alpha has messed up the mapping in a few cases as well as providing an easy method of re-editing an image if the original is lost as TGA files only have one layer. It also makes it easy to hide all unnecessary layers before using this extract alpha channel function to extract the correct information if more than one layer is present. The reason I say TGA is because that is the only format I know of being used in this way and is very common for a wide range of 3d applications. What do you think of these ideas on top on Joao's? Joao S. O. Bueno wrote: On Sunday 20 July 2008, Raphaël Quinet wrote: On Sun, 20 Jul 2008 21:22:11 +1000, Snake Arsenic [EMAIL PROTECTED] wrote: Okay I made a feature request at http://bugzilla.gnome.org/show_bug.cgi?id=543810 but it's missing a solution that will not remove any functionality. [...] Hi! Going beyond all of Raphael's excelent remarks, I still see some issues here : 1) The ability to ciew teh layer sans transparency and edit the alpha channel as if it where any other channel is provided in GIMP - you copy the alpha channel to the layer's mask, and edit it (the layer's mask). 2) The request indeed points a thing: GIMP _has_ the ability to set each channel visible or not - in the layers channel. If the image channel is disabled in the channels dialog, channel cvaleus are considere as zero for all display operations. However, setting the alpha channel to zero in this way - which is what gimp does -is useless - you just can't see anything in the image, as it is rendered with alpha = 0 for all layers. I'd suggest that when the alpha channekll si disabled in the channel dialog, image is rendered with alpha =1.0 (255) insetead. That would: a) enable the feature thought when the ability to run channel'son and off was included; b) Make gimp attend the requesterś (Snake) needs. Maybe the bug request should be chanegd accordingly? Moreover - I really think it is a more usefull (even if seldom used) behavior for disabling the alpha. What do you say of doing it? I think that it would be a big mistake to use the alpha channel for anything else than transparency. I assume that you are asking for this because you have some program (I don't know which one) that is incorrectly using the alpha channel to store bump map information or something else that is not related to transparency. It is likely that this program doesn't use a file format that supports layers or independent channels, so its authors of have decided to hijack the alpha channel in some existing file format. The correct way to solve this problem is to use layers instead of abusing the alpha channel (or maybe additional channels, but I think that using layers would be more convenient in this case). With layers, it is very easy to toggle the visibility of the image or the bump map layer, specular map layer or whatever else you are working on. So instead of extending the mistakes done by the authors of some other software, it would be much better to know what file format has been subverted, and to perform the conversion in the file plug-in: * When the plug-in loads a file that uses this strange format, it would convert the alpha channel into a layer and mark that layer (using a special name like the GIF plug-in does for animations, because that can be edited easily by the user if necessary). * You would then be free to edit the image in GIMP and modify the layer containing what should be visible or the layer containing the bump map. * When saving the file, the plug-in would detect that some layers have a special name and would then combine these layers in a way that can be read by whatever other program you are using. So I suggest that you: 1) Identify what file formats need some special treatment. 2) Check if there is a way to detect what files using that format are special, so that we do not have to ask the user every time if a file using that file format should be read in the intended way (alpha channel = transparency) or in the non-standard way (bump map). 3) Suggest improvements to the corresponding file plug-ins, instead of requesting major changes in the GIMP core. -Raphaël ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
