CMYK and Gray Color Space Conversion

Hi All,
I have read the Adobe Photoshop CS3 SDK and found Color Space Suite which will color conversion, but i can't able to find sample code.
Can anyone guide how to convert color? or any sample?
Regards,
Selvakumar

Similar Messages

Is color space conversion destructive?

Is a simple color space conversion from RGB to CMYK, and then back to RGB a destructive process – meaning will image data be altered in a way that makes it different that the original image? Like jpg compression? I’ve been working with multi-spectral image data in 4 bands (channels) that is not recognized by PS in it’s original form (R,G,B,NIR), hence the color space swap in order to manipulate. It is a very kludgy way to work with output from some amazing imagery. If the image is trashed by doing this, it becomes another reason for seeking out a better way to edit them. If it does not negatively effect the data I have a bit more time to find a better way. So far, it’s a tough row to hoe.
Thanks! TLL ( long time no post )

The experimental evidence is that the conversion is a lossy process. Take an image & duplicate it. Change one of the images from RGB to CMYK and back.Then change the blend mode to difference and you will see the resulting image is not black, but has low level colored noise - conversion errors.
Paulo

Color space conversions to/from XYZ broken?

I have just started writing a plug-in in which I need to convert data from an RGB space to XYZ and back again. For this I am using the sPSColorSpace->Convert16 function.
Unfortunately, it seems that the conversions to and from XYZ are not performed correctly. I do not know exactly what *is* calculated, but XYZ it's not. One of the giveaways is that the result of the conversion depends on the color space of the RGB data, including the gamma. Instead, the XYZ values should be uniquely defined, independent of the source RGB space.
I have since created a work-around, by using the sPSColorSpace->Convert16 function to convert RGB values to Lab, and converting those to XYZ and back again with my own code. In this way, everything works as expected. However, it's unsatisfactory for two reasons: (1) a basic SDK function seems to be broken, and (2) my workaround is very slow, introducing 4(!) redundant nonlinear transforms per pixel.
Does anyone have similar or contrary experiences? And, assuming I haven't messed up, how should one go about notifying Adobe about this? Thanks in advance!
Simon

>XYZ is a device independent color space, not a transformation of RGB (like HSB).
That is exactly what I meant. Sorry for expressing myself poorly.
The test I did was as follows. I applied my filter as a smart filter to an RGB smart object. I then *converted* (not assigned) the RGB object to another color space using a relative colorimetric conversion. Because my filter operates in the XYZ space, the (visual) output should be unaffected by the color space conversion. Unfortunately, the output changed.
When I changed my filter to use Convert16 to convert to Lab (instead of XYZ) and back, and manually performed the Lab<->XYZ conversion, the (visual) output was indeed independent of the source color space.
My conclusion is that XYZ as calculated by the Convert16 function *is* a 'transformation of RGB', but, you are correct, it shouldn't be. The conversion does not properly account for the source RGB space.
Simon

Enabling LOG C color space conversion with cLog or sLOG footage.

Hi Gang,
I shoot Sony F3, Canon C100 and Canon 5DMk3 cameras in their respective LOG modes whenever possible.   I would like to apply the newly added LOG LUT feature designated for ARRI footage to footage from these cameras. Although LOG C is different than the other LOG modes, it should be a good starting point to color grading.
Unfortunately, I can't seem to get the ARRI Log C toggle option to appear with my footage. Apparently there is a certain Metadata Tag in Alexa footage which must make it possible for the Radio Button to appear. I basically want to trick my FCP-X interface into believing the footage is ARRI Alexa Log-C footage even though it is actually Canon cLog, Sony sLog or Cinestyle. Yes, I know the Alexa Log-C profile is a bit different from the ideal profiles for each of these cameras, but it should be close enough for my needs. I will then fine tune each individual camera's color corrections using the FCP-X color panes. What I want is the Curve effect which is difficult to mimic using the Standard Color Panes. BTW, I've been using a 3rd party effect called Natress Curves for this until now, but would like to start using the built-in LUT feature instead since my company has multiple editbays which lack 3rd party plugins. Also, using the built-in color space conversion looks much simpler than the techniques I've developed for the Natress Plugin.
Can anyone tell me which metadata tag is necessary in order to activate the LOG-C LUT option?   Thanks Matt Thomas

Thanks for the reply BenB. I appreciate your willingness to help with this topic, but I'm not sure you understand what I want to do and why.
I want to use the LUT for its Luma curve in actual color corrections in FCP-X. I am not trying to use it for display of dailies or other uses which are common with LUTs.
LOG space color space is similar, but not identical with many cameras.   ARRI LOG-C is also very similar to the color space used in Cineon and DPX film scans which I used to see regularly. The black points may vary, but I can adjust black points in many ways. The general shape of the LUT curve should be very similar to other curves used to correct other LOG spaces. If these curves were dramatically different from eachother, they wouldn't be defined as LOG space. LOG is a mathematical formula for how the bits are arranged and reserved in the file structure which is somewhat similar to how stills photographers manage Zone System exposure indexes There is no magic about the way ARRI defines this. It is a way for ARRI footage to match 35mm scans easily and other cameras using LOG space such as the ones I am using regularly. I would LOVE to have Apple include specific LOG LUT's for each camera which I use, but since they have not done that yet, I would like to experiement with the included one which is designed for ARRI LOG-C.
I am a very experienced professional and understand very well how and why LUT's are being used in many ways across the industry. Yes, I use Resolve for certain tasks and yes, it is the best place to do advanced color work. The new Resolve LOG color correction pane is very useful and superior to all tools I've seen.   But I also use and enjoy the convenience of keeping my material within FCP-X as much as possible. And in many cases, FCP-X color correction tools are adequate for my needs. But when using Cinestyle, cLOG or sLOG footage on my cameras, controlling the rolloff of highlights is very difficult to do with the simple 3-way controls. in FCP-X.
Since FCP-X has no Luma or RGB curves tool built-in, I currently use the Nattress Curves plugin in an Adjustment layer over my timelines to provide a basic film look. The downside to this is that not all my editbays have licenses for the 3rd party plugins, and also there are some odd workflow issues which would be much simpler to manage the way that FCP-X does with Arri LOG-C footage.
My question is how to trick FCP-X into thinking the footage is LOG-C so I can use the newly added checkbox to interpret the footage using the LOG-C LUT in an early stage of color correction while the footage is still managed in Floating Point color space.
The LOG-C profile in the Nattress plugin works as a very good starting point for advanced color correction for footage shot by Sony F3, Canon C and Canon Cinestyle cameras. In fact, it is also a fairly good starting point for GoPro Hero3 ProTune footage as well. I am not attempting ot use the LOG-C LUT solely for color correction. Instead, I want to use it for CineGamma tonal correction which is only possible with a proper luma or RGB Curve.   I will then use the FCP-X color panes to ad specific modifications to each camera's footage to more closely match what I'm looking for. If I'm dealing with a camera with lower dynamic range, I adjust the FCP-X panes to compensate for that particular camera, then Paste these attributes to all the clips from that camera. This often results in a very good match from camera to camera while using the same LUT for the tonal look.   I would like to test this technique using the built-in ARRI LOG-C feature, but unfortunately, cannot until FCP-X allows me to use the LUT on other kinds of footage.
I hope this makes sense.   Keep in mind I am a very experienced and technical user and have a long history in the blogosphere and forums about these kinds of topics. I have very specific reasons for why I want to do this, and until Apple provides other LOG correction tools or a bonafide Curves tool, I am seeking to find a way to use the LOG-C as an alternative solution. BenB, it could be that Apple has closed out the LUT from other types of footage because of comments from their close peers which are not exactly helpful to actual real-world users. There are many more cLOG, sLOG and Cinestyle users using FCP-X than there are ARRI users and it is unfortunately they chose to limit their features to exclude these somewhat arbitrarily. My goal is to find a workaround for this odd decision and would love any tips or suggestions if the answer lies in the footage Metadata.

Script for color space conversion RGB to CMYK - URGENT Help Wanted

Excuse my ignorance with the basic nature of this question, I don't use InDesign, but I do have a pressing problem regarding it.
My book publisher has just emailed to say that my photography book has been set for the printers in InDesign and the photographs have AdobeRGB color space (which was what I was aksed to send.) The printer needs the images to be in CMYK. The publisher said that he was "pretty sure Adobe Acrobat converts the InDesign files to CMYK" and that he has sent the printer RGB images in the past and they "came out OK". He said that if this will not work, he needs to convert all of the images separately to CMYK.
Can you help with the following:
1. Is he right about the above - can Adobe Acrobat convert the files?
2. Can anyone offer me a script that will convert all of the images in InDesign to CMYK? or will he need to change them individually?
Thanks for any suggestions with this urgent request.
Stephen

1. Acrobat can convert.
2. No need for a script, if the printer needs CMYK, you can export a CMYK pdf.
3. To get the highest quality conversions, you might want to do it in Photoshop.
4. If the images are color managed and the printer has a modern work-flow a color managed RGB PDFX-4 pdf is probably the best way to go...
Harbs

Color space conversion due to transparency ...

Hi there!
Let's assume we have a document that contains two RGB images, one of them is set to 70 % transparency. When printing to PDF, the 70 % transparent RGB image is converted to CMYK, the other one retains its RGB color space ...
I seem to understand that this is due to the current transparency color space setting. I could change that to RGB.
But I wonder: Is there no way to keep the color space here, no matter if it is CMYK or RGB the images are coming with?
Thanks,
Klaus

Klaus,
To learn what happens with flattening and color, you should refer to this excellent document, "Transparency in Adobe Applications: A Print Production Guide."
http://www.adobe.com/designcenter/creativesuite/articles/cs3ip_printprodtrans.pdf
Here's are relevant section (page 24):
Printing transparency: step-by-step
When printing a page containing live transparency from InDesign CS3 and the Transparency Blend Space is set to Document CMYK, the following steps will take place (steps 3 and 6 may perform color conversions):
1 Transparency is detected on a spread by the Flattener.
2 The Flattener refers to the Transparency Blend Space setting to determine the appropriate color space in which to blend transparent objects. In this example, Document CMYK was selected. The Document CMYK color space is determined by the active color settings (Edit > Color Settings).
3 Any image that is tagged with a color space that differs from the selected blend space is converted to Document CMYK.
4 The Flattener flattens the transparency.
5 The flattened data is passed to the print engine.
6 The print engine compares the color information in the flattened data with the Printer Profile color space set in the Print dialog box. If the color settings dont match, the print engine converts the colors to the color space indicated by the Printer Profile.
7 The color-managed job is printed.

Different results of color space conversion

I am converting a raw image.
1. First in ProPhoto, passing it to PS CS3, accepting ProPhoto (against the working color space), and then I convert it in sRGB in Edit.
2. Next, converting it in ProPhoto, but when CS3 receives it, I ask for immediate conversion in sRGB, the working space.
3. Third, I change the color sapace in ACR to sRGB and pass the image to CS3.
Of course, the ACR adjustment parameters are identical in the three processes.
1 and 3 are almost identical (a difference layer does show differences, but I don't see them on the results without huge boosting, and that shows quite random, noise-like difference).
However, 1 and 2 are *vastly* different. The difference, boosted by 2 EV clearly shows the original texture, which is determined by a pecularity in the blue channel.
What is the explanation for the difference between the two conversion from ProPhoto to sRGB?
The conversion engine is Adobe (the conversion immediately at receiving the image does not ask me for the engine).
http://www.panopeeper.com/Download/ProPhoto_to_sRGB_Discrepancy.tif contains three layers with the three versions.
http://www.panopeeper.com/Download/ProPhoto_to_sRGB_inProPhoto.tif is the unconverted, i.e. ProPhoto version.

> I played around a bit with your samples and I could get close to your "Converted when receiving" version by using the Microsoft ICM engine (other options like Dither and Black point comp didn't produce big differences that I could see). Is it possible that is what you have as the engine in Edit>Color Settings?
As I posted, I am using the Adobe engine.
> I reproduced your exact steps (but in CS4), and there was no difference whatsoever between the three. Pitch black in difference blend mode.
I don't understand how you reproduced these steps. The file I uploaded is already in sRGB.
Anyway, I repeated the entire procedude carefully, the result is the same.
The raw file can be downloaded from http://www.panopeeper.com/Download/CCC_ISO0100_01208.ARW, the adjustment parameters are in http://www.panopeeper.com/Download/CCC_ISO0100_01208.xmp
With these files it is possible to repeate the entire process.
Pls note, that the conversion from raw to TIFF occured in 16bit mode, I converted the demo file to 8bit in order to reduce the size.

Color space conversion problem when importing JPEG's

Hi,
I'm currently playing with the trial version of LR. While importing JPEG's with different color spaces (sRGB and Adobe RGB) to LR I've noticed a strange effect: There is a small but noticable difference in color, depending if the JPEG was previously saved in AdobeRGB, or sRGB. All the images I've tested so far should not contain critical colors that exceed normal sRGB. When opened in CS2 both versions of a JPEG, AdobeRGB and sRGB, typically look perceptually identical, no matter if I leave the sRGB image to sRGB, or convert it to the working space (AdobeRGB). Also my color-managed image viewer behaves as it should. So I don't think it's a matter of the different color spaces.
Looking at the imported images in LR I would say that the AdobeRGB image is correctly converted while the sRGB image suffers from a slight reddish cast, most noticable in skin tones. The effect is not as strong as if I would load the sRGB image into CS2 and skip color conversion to my working space (AdobeRGB).
The sRGB versions of the JPEG's were obtained from the AdobeRGB JPEG's using CS2 for conversion.
Anyone else here experienced a similar problem? Is this a bug in the xRGB-to-ProPhotoRGB conversion of LR, or a feature?
/Steffen

Hi Uli,
thanks for pointing me to your thread. I followed the discussion with great interest. Actually, I think the effect I am describing here is of different nature and a LOT stronger, at least for the type of images I've tested.
I did some more experiments yesterday with interesting results:
1) When I export a processed RAW from LR to JPEG or PSD, no matter what Color Space (I tested AdobeRGB, sRGB and ProphotoRGB), and re-import those JPEG/PSD's to LR, they look absolutely identical to the RAW I started with. Also, at first glance, they look similar when opened in CS2, but only because I tested with color images. I can indeed see small differences when testing with B/W, as you described in your "Color management bug" thread.
2) When I change the color space of an PSD or JPEG inside CS2 (I used the default setting 'relative colorimetric') and save it to JPEG and then import this JPEG to LR, colors are far off. The strength of this mostly reddish color cast depends on the color space of the imported JPEG, strongest for Prophoto, less strong for Adobe and sRGB. Interestingly, when I convert the color space inside CS2 and save the result to PSD, it will display correctly when imported in LR. Another interesting side effect: the thumbnails of LR-exported JPEG's in the "Open" dialogs of CS2 and LR (I guess those are not color-managed) show the typical color-flatness for the Adobe and even more the ProPhoto version. For the CS2-converted JPEG's, all thumbnails look just a colorful as the thumbnail of the sRGB version.
3) Such an image which doesn't display correctly in LR will keep its color cast when exported again to a JPEG (not sure about PSD). So something goes wrong with the color conversion during the import of such CS2-converted images.
My explanation so far is that CS2 uses a slightly different way of coding the colorspace information in the metadata of JPEG's which somehow prevents LR to recognise the color space correctly.
Can you confirm this behaviour?
Steffen

Photoshop and working color spaces

In how many color spaces Photoshop can work correctly?
Can only work with gamma 1.8 and 2.2 ones or even with linear or L* gamma color spaces?
It is enough that the working spaces has RGB=0 0 0 mapped to L*=0 and RGB 255 255 255 mapped to L*=100?
Thank you
Marco

I don't know where in the past I read that in Photoshop the curves, levels and so on work correctly only if the image encoding color space has: pure black (L*=0) mapped to 0 0 0, pure white (L*=100) mapped to 255 255 255, the gray axis effectively acromathic (a,b=0) and the gamma encoding is 1.8 or 2.2.
These are the reasons because (I read) in the working RGB color space is not advisable choosing the monitor color profile.
Thank you for your considerations
Marco

Save PNG as gray color space

Hi all,
I've searched high and low for a good answer to this, but no luck so far:
I have an AI file that I wish to save as a mask for an app.
The image has to be:
Format:               PNG
Color space:        Gray
Alpha Channel:    No
I have set the following for my AI file: Document raster effect settings: Colormode: Grayscale
I have changed Edit -> Edit colors -> Convert to grayscale (but the "Convert to grayscale" text is not grayed out the next time I look in the menu, problem?)
I then save the file for Web and Devices as a PNG-24 or PNG-8 (Grayscale, no dither) but no matter how I save it the file info still says that the "Color Space" of the file is RGB. I can't get it to save the file with Color Space: Gray.
I am doing somthing wrong, but what?
Any help would be greatly appreciated!!
Kind regards,
Smulan

Thanks for your answer Larry!
I was afraid of that... I tried everything.
However, I still have a PNG file on my Mac that has "Color Space: Grey" when I look att it in file information.
Incorrect file with RGB:
Correct file with Gray (not created by me):
Sorry about the Swedish . "Färgrymd" is "Color Space"
So there is some information stored in the correct file that I seem to be unable to save using AI. Maybe I need to use some other program... The files I created with Grey scale and saved are useless when creating the mask unfortunately.
Kind regards,
Åsa

PSE 10 as external editor for Aperture 3 - 8-bit TIFF and what color space?

Hi all,
I'm taking the plunge and trying PSE 10 as my external editor for Aperture 3. I understand that I need to export as 8-bit TIFF files (not 16) because PSE can't do certain things with 16-bit files. Is that right? Should I specify a color space in Aperture or leave it as "no profile selected"? (I don't know much about color spaces; I'm not a pro.) I print on an Epson RX580 Stylus Photo printer, if that matters.
I'll be grateful for any help and advice. Thanks.

Can I suggest you buy Philip Andrews book, Advanced Photoshop Elements 10. he explains colour spaces and much much more very clearly and exactly what can be done with 16 bit files and what you then have to change to 8 bit to accomplish. He's written basic and advanced guides for Elements since day one. Usually available from Amazon for under £20.

Color separation CMYK and SPOT Color

Hi,
I am new to the Acrobat SDK and I need to write a plugin for separating the colors (CMYK and Spot)
from a PDF file. I Believe I need to use the Acro_Color library classes for doing this. Can you please
point me some sample code fragments to achieve how to separate these colors and generate a separate
PDF file for each color.
Kindly help me in this.
Thanks in advance..
Thanks
sabdul

Do you actually need to do true separations, where each page of the new
PDF is a separate "plate" OR just simple separations of objects?
If the latter, then just walk through the objects (PDEdit APIs) and copy
them from one to another.
If the former, there are a variety of methods - some simpler than other.
Depends a LOT on your specific requirements with respect to PDF levels,
standards compliance, etc. You will probably need to talk to some people
in the print production industry to better understand the specific
requirements.

Photoshop and Bridge Color Space Mismatches

I've recently scanned a number of photos (.TIFF) using the Wide Gamut Color Space (Nikon AdobeWide 4.0.0.3000).
Bridge shows:
Color Mode = RGB
Color Profile = Nikon AdobeWide 4.0.0.3000
However when I open them using the embedded profile, Photoshop CS5 shows on the file Info/Camera Data Tab
Color Space = sRGB, or
Color Space = Uncalibrated.
I opened the files in IDImager to see what it showed. It had under Technical Data
Color Space = AdobeRGB
Color Profile = Nikon AdobeWide 4.0.0.3000
So, Bridge and IDImager seem fine; Photoshop seems to have some difficulty.
The monitor is calibrated.
Why would Photoshop behave in this way? Is there anything I should be concerned about in what PS may be doing.
Dale

Probably something to do with your Edit->Color Settings. Is the second RGB dropdown set to Convert to Working RGB?

Camera calibration tab and camera color space

Hi, I need a confirmation about the hue and saturation sliders on the camera calibration tab. They are there for fine tuning the camera color space primaries in a DNG profile? Thanks a lot.

Hello, here I'm again.
I'm probably in the wrong forum, because I can't tell you anything about the DNG secrets
(though I have the specs).
About your second question (more an issue for a color science forum), I've found something:
Estimation of the primaries for a digital camera:
Please refer to these docs:
(1)
Concerning the Calculation of the Color Gamut in a Digital Camera
Francisco Martínez-Verdú et al.
http://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CEMQFjAB&url=http%3A%2F %2Frua.ua.es%2Fdspace%2Fbitstream%2F10045%2F973%2F1%2Fproof_final.pdf&ei=uL8UU8-dKYO9ygORs IKADQ&usg=AFQjCNGKNGHQZJoHu_dc2JwQwtLXOpsTBQ&bvm=bv.61965928,d.bGQ&cad=rja
(2)
http://docs-hoffmann.de/leastsqu16112006.pdf
Given is an equation
(*) X = C R
We have two applications:
(1) Original question
X = Matrix X1 X2 ... Xm
                Y1 Y2 ... Ym
                 Z1 Z2 ... Zm
m=41 values in each row for CIE CMFs (color matching functions) 380nm...780nm
R = Matrix R1 R2 ... Rm
                 G1 G2 ... Gm
                 B1 B2 ... Bm
41 values in each row for the sensor sensitivities for red, green and blue CCD array elements
Matrix C is found by solving equation (*), using the pseudoinverse.
Matrix C contains the XYZ-coordinates of the primaries red, green, blue as columns 1, 2 and 3.
(2) About the mathematics
X = Matrix X1 X2 ... Xm
                 Y1 Y2 ... Ym
                 Z1 Z2 ... Zm
m=24 values for the GretagMacbeth ColorChecker
R = Matrix R1 R2 ... Rm
                  G1 G2 ... Gm
                  B1 B2 ... Bm
24 values in each row for the RGB results als delivered by the camera, for instance in sRGB.
Matrix C contains the XYZ-coordinates of the effective primaries(including sRGB) red, green, blue as columns.
(2) explains the principle of the pseudoinverse for overdetermined systems of linear equations.
(1) explains the application for the identification of camera primaries for given sensor sensitivities.
Unfortunately, the whole concept will fail, if the camera sensor sensitivities (CMFs) are not
linear combinations of the CIE CMFs x-bar, y-bar, z-bar. In this case, a camera does not have
primaries, but the computational result can be used as an approximation.
CMF = color matching function (CIE)
I regret –it cannot be explained 'for the layman'.
Best regards --Gernot Hoffmann

SRGB monitor and SRGB color space in After Effects

Hello, I would like to ask some really basics about color correction. I do mostly animations and editing that plays on web and television sometimes. Im using a dell 2713hm monitor. Should i use the sRGB profile when i color correct? Also should i set my After Effects also to sRGB color space? thanx

My monitor comes calibrated in sRGB i think. But in any case, i m getting the spy4elite tool these days so will fix this issue.
So lets suppose it is. And please lets keep the explanation as simple as possible, cause i have read A LOT and i got confused.
From my understanding when having 8bit and i need to export for web, i should use the sRGB both in profile monitor, in AE color management and in output module? If that is correct, i wanna know what i do when i do 32 bit compositing, and also what i do when i got things for television (either motion graphics/3d or footage)
thanx

CMYK and Gray Color Space Conversion

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