Re: [Gimp-developer] CMYK file export plug-in
On 03/22/2011 01:37 AM, Jacek Poplawski wrote: On Mon, Mar 21, 2011 at 11:30 PM, gespert...@gmail.com gespert...@gmail.com wrote: Most of the people ask for CMYK because: I need CMYK support for photo retouch, to create better colors. CMYK is no different than LAB, HSV or RGB. It is colorspace like others, but uses 4 channels instead 3. CMYK is fundamentally different than LAB, HSV and RGB. In order for RGB values to make colorimetric sense, meaning that the CIEXYZ tristimulus values are known, all you need to know are the primaries and the white point used. The tristimulus values for a set of CMYK values depends on the characteristics of the pigmets, the pattern in which the colorants are arranged on paper, the order in which they are applied, the illuminant used, the characteristics of the paper they are applied on, and even the age of the print. Another difference of the CMYK color space compared to e.g. RGB is of course it's subtractive nature, meaning that as you increase CMYK values, the resulting color will be darker, whereas with RGB, larger values means a brighter color. HSV is just a different representation of RGB values, and LAB values makes colorimetric sense by themselves, without any additional information. That CMYK is fundamentally different than light based additive color spaces is the reason why GIMP developers considers CMYK somewhat of a special case we can take care of later, we first need to make a program that is powerful in the additive color space world. / Martin -- My GIMP Blog: http://www.chromecode.com/ Why GIMP 2.8 is not released yet ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
Jacek - you don't need CMYK for photos [I need CMYK support for photo retouch, to create better colors]. CMYK eventually will kill some nuances - being dependent on the paper (or other support) color. RGB colors on screen make use of luminance of the screen pixels - you can have many nuances of a base color because you can control the pixel luminosity. CMYK is made for help transferring as much color as possible from screen (other color spaces) to paper - the only white (read light) come from the printing support (paper, plastic, etc). True, there are some special colors with fluorescent additives - but they can't go everywhere. That's why CMYK is not so equal with other screen based color spaces. On short, CMYK can not reproduce the same number of colors. The assumption that 4 channels is better than 3 is wrong on this case. You can only make sense working in pure CMYK when you want to have a very precise reproduction - but for this goal you need to know exactly the paper they use (printers) and color profiles they use for the offset. The best is to send them your work in RGB [16 bits / channel - for smoothest gradients ] and your monitor profile, then they will know how to get it right. Think that for RGB to CMYK you loose something anyway. 2011/3/22 Jacek Poplawski jacekpoplaw...@gmail.com: On Tue, Mar 22, 2011 at 4:52 AM, Alexandre Prokoudine alexandre.prokoud...@gmail.com wrote: On 3/22/11, Jacek Poplawski wrote: I need CMYK support for photo retouch, to create better colors. CMYK is no different than LAB, HSV or RGB. It is colorspace like others, but uses 4 channels instead 3. Right, all colorspaces are equal, but some are more equal than others :-) The willingness to go from a wider gamut to a narrower gamut for editing what will then go to a different color space once again is, er, equally amazing :) I just mean that they should be treated similarly :) For photography? I very much doubt that. When it comes to all things related to photography, the point is to preserve as many colors as possible. Which is how all those ProPhotoRGB and the like were introduced all those years ago. Jumping between wide and narrow gamuts effectively kills useful information. Hardly better colors, sorry. I was influenced by Dan Margulis. I try to follow his ideas in Gimp, instead Photoshop. He generally assumes that photography is made from 10 channels: R, G, B, L*, A*, B*, C, M, Y, K and you can use any subset of them to generate good quality image with good colours. (http://en.wikipedia.org/wiki/Dan_Margulis) And everything works as expected, with the exception of realtime preview. I just decompose image to LAB or CMYK then use these layers for increasing contrast, masking, etc... but using curves in LAB or CMYK is very hard without preview, because you have to imagine colors. The good thing is that GMIC has support for these colorspaces now, and RawTherapee is developing fast. PS. sorry for offtopic ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer -- Nemes Ioan Sorin ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
On Tue, Mar 22, 2011 at 8:19 AM, SorinN nemes.so...@gmail.com wrote: Jacek - you don't need CMYK for photos [I need CMYK support for photo retouch, to create better colors]. I am familiar with this opinion. I don't want to continue offtopic discussion in this thread, so I just give one example: curves. You can get more interesting retouch when using curves in CMYK and in LAB and in RGB than using only RGB curves. You can get more data from shadows by using K curve in CMYK for instance. You can increase contrast without touching the colors by using L curve. etc ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
On 03/22/2011 08:25 AM, Jacek Poplawski wrote: On Tue, Mar 22, 2011 at 8:19 AM, SorinNnemes.so...@gmail.com wrote: Jacek - you don't need CMYK for photos [I need CMYK support for photo retouch, to create better colors]. I am familiar with this opinion. I don't want to continue offtopic discussion in this thread, so I just give one example: curves. You can get more interesting retouch when using curves in CMYK and in LAB and in RGB than using only RGB curves. You can get more data from shadows by using K curve in CMYK for instance. You can increase contrast without touching the colors by using L curve. etc We are talking about techniques to retouch photos on a mailing list for the development of an image editing application, so this is not offtopic. Why would you transform to CMYK to lose color information just so you can increase the K value, rather than making a lossless transformation into LAB and decrease the L value? Note that with GEGL, we will easily be able to have adjustment layers that work on the L component in CIELAB. / Martin -- My GIMP Blog: http://www.chromecode.com/ Why GIMP 2.8 is not released yet ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
My current workflow: 1) choose photos in Digikam, copy them to another folder 2) open photo in RawTherapee 3) try to get good colour and contrast in RT, fix highlights, etc, then export to Gimp (RT has no layers) 4) use RGB curves in Gimp, sometimes decompose to RGB and combine layers to create BW version 5) use color mixer in GMIC, LAB mixer is good to create toned down version of colors, CMYK is mixer is good to fix colors different way (or use GMIC for quick BW version) 6) healing tool (only Gimp can do this) 7) save xcf, export jpgs The thing I miss are LAB curves and CMYK curves. I asked GMIC developer for LAB/CMYK curves support and it is there, but UI is hard to use. RawTherapee has support for LAB curves and they work very good (and in 16bit mode), but there are no layers in RT. So I am fan of RT, Gimp and GMIC, this is very good, quite mature free software. I am also aware of Photivo / LAB Curves. Never tried Darktable and Krita for photos. After looking at all available solutions the only way I see for me is to develop simple application (of course GPL) which will open jpg/tiff, process image in RGB/LAB/CMYK with curves/mixers/blend modes then save tiff/jpg again. But I will announce it when ready (or won't if I fail). PS. CMYK is also best colorspace for skin color retouch by numbers, that's why I wanted to fix CMYK values in Gimp colorpicker, but there was big discussion on this mailing on this subject ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
On 03/22/2011 08:20 AM, Martin Nordholts wrote: LAB values makes colorimetric sense by themselves, without any additional information. Correction: For CIELAB values to make colorimetric sense, it is necessary to also know the reference white point. / Martin -- My GIMP Blog: http://www.chromecode.com/ Why GIMP 2.8 is not released yet ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
[Gimp-developer] Can't paste into Gimp with custom clipboard program
I recently wrote a program to handle copy/paste of text and images using X11 for Linux. Most things are working nicely, I can copy an image to the clipboard and sucessfully retrieve it and I can paste images copied from other programs. My problem however is that if I use my program (xcsi) to copy an image, then I can't paste it into Gimp (not Inkscape either). My program logs all selection requests made by other programs, and I can see that Gimp requests the TARGETS selection from my program several times. The paste option is not grayed out in Gimp after copying an image with my program, but Gimp never makes a request for image/bmp or image/png when my program offers it. Can someone help explain how Gimp handles pasting and how I might get this working please? At first I thought it was a problem with Gimp because it never requests the image, but copying from Firefox and pasting into Gimp works, so maybe it's something I'm doing wrong then. The source code from my latest version of the program is here on an Allegro forum thread : http://www.allegro.cc/forums/thread/606034/909368#target Using openSUSE 11.3, and Gimp version 2.6.8-6.1. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
On Tue, 22 Mar 2011 09:14:43 +0100 Jacek Poplawski jacekpoplaw...@gmail.com wrote: PS. CMYK is also best colorspace for skin color retouch by numbers, that's why I wanted to fix CMYK values in Gimp colorpicker, but there was big discussion on this mailing on this subject Martin: I don't know if this originates with him, but a reference for this can be found in Skin by Lee Varis. He describes a ratio of C-M-Y which can be used to numerically adjust skin tone in an image. This ratio appears to be based on PSes internal CMY(K) colour profile and thus (I've since discovered) probably has no bearing on anything! Jacek: My suggestion would be to use a calibrated monitor and an image which has been curve adjusted in PS to get the skin tones numerically correct, and then to learn to do it by eye. I think that the numerical method is good for starting out, but after a while you should be adjusting to what *you* want, not what the numbers suggest! :-) Jon ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
[Gimp-developer] GSoc 2011 - Adaptive Image Cloning
Hello, My name is Robert Sasu and I study Computer Science at Polytechnic University of Bucharest, Romania. I would like to participate to GSoC 2011 and I found the Adaptive Image cloning project interesting. I have strong background in C/C++ and C# programming, algorithms and I have also done some projects with image filtering. I really like mathematics:I recently participated to SEEMOUS(seemous.eu) and I earned a silver medal. I compiled Gimp from Git and looked over the coding style and the algorithms used by gimp. I've read about the mean value interpolation, starting from the mvclone pdf and then searching in google for more explanation. I would like to now how important is this project for you and what your requirements and expectations from the students applying? Do you want to implement the mean value interpolation algorithm or you want to finish the Laplacian method used by gimp? I think in the implementation of one of this algorithm we should use the selection tools from gimp and for the healing certain brush elements. If it is possible we could also implement Matlab(Octave) code for increasing the performance of calculating pixel values. It would be also possible to add another aspect by letting the user choose a border within he/she wants the inserting(the interpolation). It would be easy to implement MVC matting to help the user and then giving him the chace to put the selected part of one image in the other. Thank you, Robert Sasu ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
2011/3/22 Jacek Poplawski jacekpoplaw...@gmail.com: CMYK is also best colorspace for skin color retouch by numbers, No it isn't, because unless you go through a lot of extra work to avoid it, colors in the image that the used CMYK color space is unable to represent will get lost. / Martin -- My GIMP Blog: http://www.chromecode.com/ Why GIMP 2.8 is not released yet ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
No it isn't, because unless you go through a lot of extra work to avoid it, colors in the image that the used CMYK color space is unable to represent will get lost. True. Lot of work in studio then offset hardware will trow out different things ..because : paper quality, paper type ( coated / uncoated ) which affect reflection of white light (color nuances) ..hardware color profile ..etc. 2011/3/22 Martin Nordholts ense...@gmail.com: 2011/3/22 Jacek Poplawski jacekpoplaw...@gmail.com: CMYK is also best colorspace for skin color retouch by numbers, No it isn't, because unless you go through a lot of extra work to avoid it, colors in the image that the used CMYK color space is unable to represent will get lost. / Martin -- My GIMP Blog: http://www.chromecode.com/ Why GIMP 2.8 is not released yet ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer -- Nemes Ioan Sorin ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
On 3/22/11, Jacek Poplawski wrote: I am familiar with this opinion. I don't want to continue offtopic discussion in this thread, so I just give one example: curves. You can get more interesting retouch when using curves in CMYK and in LAB and in RGB than using only RGB curves. LAB curves are fine. Transparent work in LAB makes sense, but the prerequisite is still GIMP 3.0 with high bit depth precision, otherwise you still lose color data due to rounding errors in 8bpc mode. Reference 1: http://brucelindbloom.com/index.html?RGB16Million.html Reference 2: http://bit.ly/gIjQUh You can get more data from shadows by using K curve in CMYK for instance. Oh come on. K curve is simply not the only and even not the best way to work on various tonal ranges selectively. Check out zone system implementation in both commercial LightZone and free-as-in-speech darktable. Alexandre Prokoudine http://libregraphicsworld.org ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] CMYK file export plug-in
On Mon, Mar 21, 2011 at 5:30 PM, gespert...@gmail.com gespert...@gmail.com wrote: Those operations are: - Combining the alpha channel of the pure C, M, Y, K areas with the corresponding separated channel via screen blending mode. - Converting desired CMYK percentages to grayscale values and fill the selection (the alpha of the area that should have a specific CMYK) with the resulting values for each layer created by Separate+ The resulting file will be perfectly fine, but reaching that point is tedious and several things can go wrong in the process. So, what if the ideas of spot layers is applied to Separate+, using naming conventions to define what to do with them? This approach you outline would solve most of the use cases I have for CMYK (overprint, underlay (for dark substrate), one or more CMYK as spot/solid color, rich black). What I really miss from photoshop is the poorly-named apply image command. It basically allows you to combine any two channels using the available blending modes (Multiply, Screen, etc.). Right now, I have to do a lot of bouncing back and forth between layers, selections and channels. But that's probably well beyond the scope of what you're suggesting so I'll shut up now ;) Chris ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
[Gimp-developer] GsoC - 2011 - Porting GIMP plugins to GEGL operations
Hello, I am Robert Sasu and I wrote an e-mail in the morning about the application for the Adaptive Image Cloning. Since then I've spoken with mentors on IRC, and they said that this project is no more available. I was also recommended to look at Porting GIMP plugins to GEGL. As I wrote in my last e-mail I have strong C/C++ and algorithms background and I have done some image processing/filtering projects. I've also compiled GIMP from GIT with all the libraries and dependencies. I also looked over the coding style and started to familiarize with the code in GEGL and GIMP. I propose simply to rewrite GIMP plugins in gegl operations as there are many predefined functions, and the implementation is not so hard. How important do you find this project, compared with others for this years GSoC? I would like to know which are the plugins I should start to look at and port to GEGL. I would also ask for some specific information about this project. How did you imagine the porting: by rewriting the entire code for every plugins doing some adaptation to the logic? Thank you, Robert Sasu ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
[Gimp-developer] GsoC - 2011 - Porting GIMP plugins to GEGL operations
I've read the e-mails about this project from the mailing list and I found actually what I have to do. I also looked at the source code and the differences between gimp and gegl implementation. If it is possible I would like a short list of plugins to look at, which are needed to be implemented ? And again: how important do you find this project compared to others for this years GSoC? Thank you, Robert Sasu ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] GsoC - 2011 - Porting GIMP plugins to GEGL operations
Robert Sasu wrote: I am Robert Sasu and I wrote an e-mail in the morning about the application for the Adaptive Image Cloning. Since then I've spoken with mentors on IRC, and they said that this project is no more available. I don't know who told you that or why but Adaptive Image Cloning (aka Seamless Cloning) is on the list of possible GSoC projects for this year. The student application period doesn't open until the 28th of this month so all projects are up for grabs at this point. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] GsoC - 2011 - Porting GIMP plugins to GEGL operations
On 3/23/11, Kevin Cozens wrote: Robert Sasu wrote: I am Robert Sasu and I wrote an e-mail in the morning about the application for the Adaptive Image Cloning. Since then I've spoken with mentors on IRC, and they said that this project is no more available. I don't know who told you that mitch and Alexia or why The agreement was not to introduce new tools based on old core, and GEGL based tool here means underlying GEGL painting infrastructure which is simply not ready yet. Alexandre Prokoudine http://libregraphicsworld.org ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
