This is a bit of a cross post from Chromix's colorforums.com but I don't think that gets nearly as much traffic as LL so I wanted to see if anyone here has any experience with this. I've left a message with support but I figured the community here might have suggestions for alternative methods of getting a list of colors from a target. It's really easy with targets created for ProfileMaker as the reference file is in RGB and that can easily be pulled into a spreadsheet. Same goes for Colorport, just pull the .tab file into a spreadsheet as it uses the RGB values. Argyll however uses L*a*b* to specify target patches. I visited Bruce Lindbloom's site to get the equations to convert from Lab to XYZ and then to RGB but... yeah I'm just not that smart. I figured I could just use ColorThink to extract the values from the TIFF file but in doing so I noticed WAY more colors in there than should have been. With other targets you can do this and clearly see some patterns emerge but it doesn't work nearly as well with Argyll targets. Perhaps it would work better if I uprezzed the file (haven't tried that) as there may be less sample points falling on transitions. Anyhow, here's the original post:
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I'm running ColorThink 2.2.1b5 on OS X 10.6.3. I'm trying to create a color list that I can look at in a spread sheet so I can see what Argyll is doing when generating patches. The first attempt I noticed that there were a lot more colors than there really were (this is a 1728 patch target) so I took a closer look and noticed that there is a 1 pixel transition between some, but not all of the patches. I used a fixed size marquee in Photoshop to delete those transitions and tried again but still I'm getting very unusual results. In the spreadsheet I've sorted by ascending R,G,B values and have filtered out the duplicates. I should in theory have 1728 discrete colors but it's showing 4200 discrete values. (I generated a generic target using targen -v -d2 -G test1728, and printtarg -v -iSS -pA4R -t test1728). The target definitely only has 1728 different colors in it.
I also tried this on a target which was generated by Monaco Profiler. MP is generating predictable evenly distributed patches. You can see some of that yet the color list is showing FAR more colors than are actually there in the target.
As a test I created a file that was 1200x800 pixels. I filled 400 pixel increments with red, green and blue respectively, saved and then extracted the colors. What I would expect would be 6600 samples but only 3 different colors that were 255,0,0; 0,255,0; and 0,0,255. What I ended up with (after filtering out the duplicates) was:
0,253,0
5,169,77
16,0,230
85,169,0
255,0,0
I guess I expected that "export color list" would generate a list of every discrete color in an image. I guess in a regular photograph that might be impractical as that could be quite a large number so after thinking about it for a while... it seems as if it may be just taking samples at some pre-determined x,y spacing but with an aperture that's larger than 1 pixel and this is why I'm seeing more than 3 colors in this particular test.
Would that be accurate?
Cheers, Joe