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A number of people have requested CMYK support, but that raises the question of exactly what features need to be implemented to support CMYK properly.
One of the largest uses for CMYK that I would have (along with LAB) is the ability to manipulate the channels for achieving different effects and corrections, not necessarily for saving separations. Is it possible to have some type of interface that gives the user the look that they are working in another color space while the actual image changes are made in the cores internal RGB space? later, Tom
I'm very pleased that Cinepaint will be supporting CMYK for pre-press work. I will try to give you a few guidelines to the best of my "limited" ability. Most pre-press users who are accustomed to Photoshop will be looking for the following:
1. The ability to handle common types of files...i.e. .jpeg, .psd (native Photoshop files), .eps (encapsulated post script), .png. .tiff and bitmaps (.bmp).
2. The ability to separate the image into four separate channels, edit the levels on each of these channels and then re-combine them into a coherent image (merge layers).
3. Appropriate tools to enhance the image, similar to what is now present in GIMP.
4. A nice tool to have would be an interactive transparency tool that would enable the operator to apply transparency gradually to areas of the photo.
5. Absolutely necessary: The ability to insert text that is smooth, easy to stroke/fill/resize on-the-fly.
6. A menu of special effects similar to GIMP or Corel PhotoPaint.
7. The interface that is currently used for the GIMP and Cinepaint is more than adequate (Cinepaint's is much like Photoshop now), but you must include a CMYK Pallette to assign colours.(Colour wheels are traditionally used, with an eyedropper tool to pick the required colour).Also an optional colour designator, where various percentages of the 4 channels can be defined by the user (Cyan, Magenta, Yellow and Black) to get an exact match for the colour they are looking for, very similar to the RGB and HSV colour editor you now have in Cinepaint, but add the four CMYK channels.This is a very important tool for anyone in the graphic design business.
8. The option to save the finished work as a CMYK tiff or eps file, as these are the most commonly used formats for print work.
If the above can be fully integrated with the present features of Cinepaint, you should come out with a winning product.Perhaps a visit to your local newspaper pre-press department could be arranged. (Usually they are most eager to impart their knowledge to inquiring minds!) If you need more detailed info, or if there is anything else I can contribute, please let me know.
The basic need is to produce an output file, such as a TIFF file, that was in CMYK rather than RGB color format. Beyond that, the color manipulation tools in gimp should be workable in the CMYK model. For example, when curves are selected there should be curves for cmy, instead of rgb as an option.
The display will always be in RGB even if the file is CMY(K). so there needs to be something going on behind the curtain to translate the image on the fly for display purposes. But I have created cmyk versions of e.g., photographs and they displayed OK using standard display programs (the colors were a bit dull.)
The safest guide would be to get a Photoshop manual or book and see what that program offers in terms of CMYK features. I don't have one but I'll check the library.
And I will ask around on a few mailing lists where PHotoshop users hang out.
I need to be able to do the following:
Convert from RGB to CMYK colour space:
- I need to be able to set the source profile. (For most images I use sRGB as the source profile, but if I had a colour-calibrated scanner I would need to use its own profile...)
- I need to be able to select the destination profile. (For most images I use the SWOP Coated profile from the Free Adobe ICC profiles zipfile)
- The ability to select the rendering intent might be useful in some circumstances, but I don't personally need it - I use the "Perceptual" intent most of the time.
Editing of images:
- The vital feature for me is being able to edit the four plates individually. There are occasions (especially with non-photographic images) where a black feature (maybe some text) knocks out the coloured plates. This isn't always desirable, and the ability to paint the coloured plates back in is very useful. (It means that if the printing press doesn't register perfectly, you don't get a white fringe around the black feature...) Proofing (i.e. previewing on the Monitor what the finished printed article would look like) would be useful, and lcms allows the use of an "alarm" colour - a colour that will show through where a colour can't be represented on the target device.
Loading and Saving:
- Embedding the ICC profile into TIFF images would be useful, but I've lived without this feature so far...
You might also want to incude a link to my GIMP plugin, just so that anyone who's interested can play with an existing (albeit hacky) implementation.
If you don't mind, my updated comments for your CMYK page: Most of my photography is nature/wildlife/landscapes, used in magazines, books, the web, and fine-art prints. I currently have little need for CMYK support directly, but having it would let me take control of more steps in the process.
Also, I would point out that using colourspace conversion would seem to be the perfect vehicle for CMYK support, as well as these other abilities. Think "ICC profiles". The ability to have my monitor profiled, and have CinePaint convert from the current working space (e.g. AdobeRGB or sRGB) to the monitor's colour space.
Not only does this setup (which I use with Photoshop) allow me to see consistent colour on multiple monitors and printers, but colourspace conversion can just as easily go to/from CMYK. For dealing with photographic images, another nicety would be proper support for the Lab colourspace, to assist things like USM sharpening only the L channel (in Gimp I cheat and decompose to HSV, sharpening only the Value channel). I think that's the pertinent bits for CMYK.
Other feature wishes:
- Flipping horizontal/vertical shots
In the Gimp there is a nice set of 90-degree rotates under Image->Transforms->Rotate, which I cannot find an equivalent of in CinePaint. However this is not a critical issue for me as I can use ImageMagick to do this on 16-bit files.
- Rotating and cropping the image
While in the Gimp I use the Measure tool to measure the angle of a line between two points that should be vertical (or horizontal), then rotate the image by that amount, and then crop back to a rectangle, this is a pain in CinePaint. There is no Measure tool, and the Transform tool's rotate function does not have a dialog to allow me to enter a specific number of degrees.
- Correcting the white balance of an image
A shortcut I often use in the Gimp is to sample the colour of something that should be white, and create a new layer filled with the inverse of that colour. Set the layer mode to "Color" (which CinePaint does not have) and vary the layer's opacity to correct it.
Certainly a more flexible method for white-balance control would be useful, both in CinePaint and in Gimp. But using the "Color" layer mode works well in the Gimp (and in PhotoShop, BTW).
There are other ways of dealing with colour casts also. See this article for a description of using Curves in Photoshop:
http://www.naturephotographers.net/mh0702-1.html
I'm not sure, but the CinePaint Curves dialog might need a few extra controls to be able to do this.
- Lack of a "CinePaint-remote" tool
My image database manages my entire workflow, including the storage of the image files themselves (part of this is managing local disk caches and libraries of CD/DVDs). When I select 'Edit' on an image it creates a small window to manage this, with the full pathname of the working file in a selectable field (to assist cut-n-pasting it to command-line tools when required) and will pass the filename to an external program. It has "Done" and "Abort" buttons: when the image editting is complete, "Done" causes the database to do things like check the new filesize and dimensions, regenerate a thumbnail, etc. A "Reinvoke" button calls the same external program again.
With the Gimp I pass the file to gimp-remote, which passes it to a running Gimp via a drag-n-drop to the toolbox window (or starts a new Gimp if none was running). It would be nice if the CinePaint toolbox supported the same Xdnd protocol to allow the creation of "cinepaint-remote": at the moment my software has to start a new CinePaint for each image.
Indeed using DnD for this is a hack, and sometimes it doesn't work (e.g. with a multiple-workspace desktop manager I've had the odd time when it can't find the Gimp toolbox - a retry has worked). For me the basic requirement is just to be able to ask the editor to open a file. The interface for me can be a command-line tool: it doesn't matter what IPC mechanism is behind that.
However, another feature which would be EXCELLENT would be a callback when the file is closed. In my current software I have a long-lived dialog with a 'Done' button so the user can tell my software when the editting is finished. Letting my software know when the editor had finished, and popping up a dialog at that point would be better, especially when working on multiple images concurrently.
I'm not sure what IPC mechanism would be best for this, but it would help if it's something I can craft Perl and Python interfaces for.
The last thing that I am is an expert on pre-press work, but with that said I will offer my opinion.
The main thing would be a basic rgb->cmyk and back again utility were out of gamut colors are displayed in an off color like neon green or something. That would make the software at least usable for pre-press, and I think that most press operators will do the final check on colors anyway.
The ability to handle color profiles would also be nice. Though in my experience the presss operator will do the final color check to make sure things are within reason. In the photography world color profile are becoming ever more popular though and I think that photographers would be very interested in this. With under X there is know color calibration software that I am aware of so the main thing would be to convert an image to something like AdobeRGB which I think is a freely available profile.
Spot colors would also be nice with the ability to save duo tones and tri tone images. Most commercial pre-press software that I am familiar with comes with a palette of pantone http://www.pantone.com colors. I do not know if pantone will give away the data on these colors for free or not, something to check in on.