Re: [Gimp-developer] Automatic white balance
Sven Neumann wrote: > Hi, > > On Tue, 2007-11-27 at 22:04 +0100, Stephane Chauveau wrote: > > >> Nice! I never noticed that the grey point picker in the level tool could >> be used to adjust the WB. It is unfortunately limited to the mid-tones. >> > > How is it limited to the mid-tones? > > > Sven > > > The black point picker is of course totally useless for adjusting the white balance. The white point picker can be very useful for white balance but, since it also set the white point, it can only be used you have a true white point in you image. By that, I mean a point that is both neutral-grey and of maximal brightness. This is usually not the case. So was it left is the 'middle-point' picker. This one sets the middle-point of the RED, GREEN & BLUE levels but without affecting the 'right-point' of those levels. In practice that means that the white balance of the current 'white point' is absolutely not affected by that picker. More generally, the more you are the highlights, the less you are affected by the 'middle-picker'. That was I mean by 'limited to the mid-tones' though I should have written 'mid-tones and shadows' since the 'middle-point' picker also affect the shadows (but in practice they are less interesting). If you are not convinced (or just don't understand me) then think about that: you cannot change a true white point (255,255,255) using the middle-point picker. However, after playing a bit with the middle-point picker, I came to the conclusion that the results are usually quite good. This is because, in Gimp, the WB is usually applied on an image that was already adjusted (AWB and exposure in the camera, ...) so the WB coefficients tend to be small (-15% to 25% on each channel), most of the image is already in the mid-tones or shadows and the parts that are in the highlight are often already white (typically the clouds). Not having to care about clipping the highlights is also nice. The situation in a tool like UFraw is quite different: The WB is usually the first transformation applied to the raw data. The WB coefficients can be huge (-50% to +100% on each channel) and are followed by some complex adjustments (ICC profile, exposure, gamma, highlight clipping and recovery, ...). ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Automatic white balance
Hi, On Wed, 2007-11-28 at 09:13 +0100, Jean-Luc Coulon (f5ibh) wrote: > > So it would be nice to be able to open a white reference picture and > pick reference from this picture an apply it to the other shots. You can easily do that. Just do the color correction using the Levels tool on one image. Then save the Levels file and apply it to the other images. If you Shift-click the Save/Load buttons in the Levels tool dialog, you do not even need to enter a filename. Of course this could certainly be streamlined further. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Automatic white balance
Le 27.11.2007 20:04:12, Stephane Chauveau a écrit : >Øyvind Kolås wrote: >> On Nov 26, 2007 2:22 PM, Weber, Dr. Martin (Allianz ASIC) >> <[EMAIL PROTECTED]> wrote: >> > >Anyways, a plug-in providing several WB methods would be cool but, in >most cases, I believe that it would be even better to extend the Color >Balance tool with the ability to manually pick the grey point in the >image. The easiest way to implement that feature could be to add a > 'Set > >White Point' button to the Color Picker tool. A nice feature in this case would be to be able to get the white point in an OTHER picture. With digital photography, I use often raw pictures. At the beginning of the shot, I get a picture of a grey/white card which will be the white reference for all the following pictures. If the light conditions change, I get an other picture of the grey chart and so I never mind of the camara white balance, all the wotk is done in post-processing. So it would be nice to be able to open a white reference picture and pick reference from this picture an apply it to the other shots. Regards Jean-Luc pgpgoamjCJzrS.pgp Description: PGP signature ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Automatic white balance
Hi, On Tue, 2007-11-27 at 22:04 +0100, Stephane Chauveau wrote: > Nice! I never noticed that the grey point picker in the level tool could > be used to adjust the WB. It is unfortunately limited to the mid-tones. How is it limited to the mid-tones? Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Automatic white balance
Øyvind Kolås wrote: > On Nov 27, 2007 7:00 PM, Stephane Chauveau > <[EMAIL PROTECTED]> wrote: > >> Øyvind Kolås wrote: >> >>> You could start out by studying the following paper, as well as it's >>> references: >>> http://www.ivl.disco.unimib.it/papers2003/WB%20Combining%20%20EI%206502-12.pdf >>> >>> /Øyvind K. >>> >>> >> Nice article. The following Wikipedia pages does not describe so many >> methods but are probably easier to start with: >> >> http://en.wikipedia.org/wiki/White_balance >> http://en.wikipedia.org/wiki/Color_temperature >> >> The following article is even less technical but is also a nice read and >> it explains the most common issues with automatic WB. >> >> http://www.cambridgeincolour.com/tutorials/white-balance.htm >> >> Anyways, a plug-in providing several WB methods would be cool but, in >> most cases, I believe that it would be even better to extend the Color >> Balance tool with the ability to manually pick the grey point in the >> image. The easiest way to implement that feature could be to add a 'Set >> White Point' button to the Color Picker tool. >> > > This functionality exists in the levels tool already. > > Nice! I never noticed that the grey point picker in the level tool could be used to adjust the WB. It is unfortunately limited to the mid-tones. The behavior I have in mind is quite different and is more like the one found in most cameras and described in the paper you mentionned (the Von Kries hypothesis): figure out a grey point to compute a set of 3 coefficients (for red,green and blue) and multiply each channel by its respective coefficient (with clipping). See for example how WB can be done in UFraw by selecting a grey area with the mouse. > Personally I'd prefer a gui similar to: > > http://pippin.gimp.org/plug-ins/color_correct/ > > for a combined levels (on luminance) and white point/gray point/black > point offset. Since I don't find it entirely natural to modify the > white point using levels. > > Me neither. The grey/white point in white balance (the illuminant tint) and the grey point in levels (the average brightness) are very different concepts. > /Øyvind K. (Doing full quote and replying to the list since the > message I reply to didn't seem > to be sent to the list.) > ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Automatic white balance
On Nov 27, 2007 7:00 PM, Stephane Chauveau <[EMAIL PROTECTED]> wrote: > Øyvind Kolås wrote: > > You could start out by studying the following paper, as well as it's > > references: > > http://www.ivl.disco.unimib.it/papers2003/WB%20Combining%20%20EI%206502-12.pdf > > > > /Øyvind K. > > > Nice article. The following Wikipedia pages does not describe so many > methods but are probably easier to start with: > > http://en.wikipedia.org/wiki/White_balance > http://en.wikipedia.org/wiki/Color_temperature > > The following article is even less technical but is also a nice read and > it explains the most common issues with automatic WB. > > http://www.cambridgeincolour.com/tutorials/white-balance.htm > > Anyways, a plug-in providing several WB methods would be cool but, in > most cases, I believe that it would be even better to extend the Color > Balance tool with the ability to manually pick the grey point in the > image. The easiest way to implement that feature could be to add a 'Set > White Point' button to the Color Picker tool. This functionality exists in the levels tool already. Personally I'd prefer a gui similar to: http://pippin.gimp.org/plug-ins/color_correct/ for a combined levels (on luminance) and white point/gray point/black point offset. Since I don't find it entirely natural to modify the white point using levels. /Øyvind K. (Doing full quote and replying to the list since the message I reply to didn't seem to be sent to the list.) -- «The future is already here. It's just not very evenly distributed» -- William Gibson http://pippin.gimp.org/http://ffii.org/ ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Automatic white balance
Øyvind Kolås wrote: > On Nov 26, 2007 2:22 PM, Weber, Dr. Martin (Allianz ASIC) > <[EMAIL PROTECTED]> wrote: > >> I think the automatic white balance of many programs as well as of GIMP is >> not always leading to optimal results. So I want to deleope a new better >> algorithm for GIMP. To be able to I would like to get as many information as >> possible about the commenly used ones. So if you know an automatic white >> balance algorithm please tell me. >> > > You could start out by studying the following paper, as well as it's > references: > > http://www.ivl.disco.unimib.it/papers2003/WB%20Combining%20%20EI%206502-12.pdf > > /Øyvind K. > Nice article. The following Wikipedia pages does not describe so many methods but are probably easier to start with: http://en.wikipedia.org/wiki/White_balance http://en.wikipedia.org/wiki/Color_temperature The following article is even less technical but is also a nice read and it explains the most common issues with automatic WB. http://www.cambridgeincolour.com/tutorials/white-balance.htm Anyways, a plug-in providing several WB methods would be cool but, in most cases, I believe that it would be even better to extend the Color Balance tool with the ability to manually pick the grey point in the image. The easiest way to implement that feature could be to add a 'Set White Point' button to the Color Picker tool. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Automatic white balance
On Nov 26, 2007 2:42 PM, Alexandre Prokoudine <[EMAIL PROTECTED]> wrote: > > On Nov 26, 2007 5:22 PM, Weber, Dr. Martin (Allianz ASIC) wrote: > > > I think the automatic white balance of many programs as well as of GIMP is > > not always leading to optimal results. So I want to deleope a new better > > algorithm for GIMP. To be able to I would like to get as many information as > > possible about the commenly used ones. So if you know an automatic white > > balance algorithm please tell me. > > Relevant part of DCRaw/UFRaw source code? > > Alexandre > ___ > Gimp-developer mailing list > Gimp-developer@lists.XCF.Berkeley.EDU > https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer > -- «The future is already here. It's just not very evenly distributed» -- William Gibson http://pippin.gimp.org/http://ffii.org/ ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Automatic white balance
On Nov 26, 2007 2:22 PM, Weber, Dr. Martin (Allianz ASIC) <[EMAIL PROTECTED]> wrote: > > > I think the automatic white balance of many programs as well as of GIMP is > not always leading to optimal results. So I want to deleope a new better > algorithm for GIMP. To be able to I would like to get as many information as > possible about the commenly used ones. So if you know an automatic white > balance algorithm please tell me. You could start out by studying the following paper, as well as it's references: http://www.ivl.disco.unimib.it/papers2003/WB%20Combining%20%20EI%206502-12.pdf /Øyvind K. -- «The future is already here. It's just not very evenly distributed» -- William Gibson http://pippin.gimp.org/http://ffii.org/ ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Automatic white balance
On Nov 26, 2007 5:22 PM, Weber, Dr. Martin (Allianz ASIC) wrote: > I think the automatic white balance of many programs as well as of GIMP is > not always leading to optimal results. So I want to deleope a new better > algorithm for GIMP. To be able to I would like to get as many information as > possible about the commenly used ones. So if you know an automatic white > balance algorithm please tell me. Relevant part of DCRaw/UFRaw source code? Alexandre ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
