But to obtain that, it seems to correspond more to the approach 2 which allows me to calculate a standard deviation…. So, I am still lost I think. It is of course possible to use both methods, depending on whether you are considering the within egg statistics or the between eggs statistics. But in any case you have to understand what you are doing and why. This is where science begins! An objective method should be found. I warmly thanks for you answer and I will do my best to understand the underlying behind the both methods Regards.
It has to do with mathematics. Please make sure you understand what the results of both methods really mean. Both represent different aspects of your data. I realise this is a very old topic but the macro is very helpful for what I want to do as well - so thank you.
Is there a way to add the photo name as the Label in the results file? I have hundreds of images to do and I want to make sure that I am not getting any results confused. I can see, that you are an imagej expert… please help me how to get HSB and Lab values for each pixels. I have already the RGB values in an excel, but I need the other numbers too… Do you have an idea how to get these values?
In Photoshop I think I can do it pixel by pixel, but it takes too much time, I have 3 images 65x35 pixels. Thanks in advance for your help and support! Hi all! Good day, yes it is possible! The variables are used to store temporary values which makes the formulas easier to read. There are two formulas to choose from in the first step. If Luminance is smaller then 0.
All values need to be between 0 and 1. In our case all the values are between 0 and 1 If you get a negative value you need to add 1 to it. If you get a value above 1 you need to subtract 1 from it.
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DevelopIntelligence leads technical and software development learning programs for Fortune companies. Helmholtz-Kohlrausch effect is one, but there are many others. In my post I was trying to cover the basic concepts as completely as possible without venturing into the very deep minutiae. The Hunt model, Fairchild's models, and others do a more complete job, but are also substantially more complex. Myndex, nevermind, my implementation was fatigue-based and my poor results came from that : Thank you very much for your help and your post which is of a great value!
Show 6 more comments. Jive Dadson Jive Dadson That is just the way sRGB is defined. I think the reason is that it avoids some numerical problems near zero.
It would not make much difference if you just raised the numbers to the powers of 2. JMD - as part of work in a visual perception lab, I have done direct luminance measurements on CRT monitors and can confirm that there is a linear region of luminance at the bottom of the range of values.
I know this is very old, but its still out there to be searched. I don't think it can be correct. It doesn't. DCBillen: no, since the values are in non-linear gamma-corrected sRGB space, you can't just add them up. DCBillen Rdb is correct. It pains me that after four years, the correct answer is rated so low.
I will get over it. Gust van de Wal 4, 1 1 gold badge 20 20 silver badges 43 43 bronze badges. Synchro Synchro The W3C formula is incorrect on a number of levels. It is not taking human perception into account, they are using "simple" contrast using luminance which is linear and not at all perceptually uniform. Among other things, it appears they based it on some standards as old as !!! Age has nothing to do with it - the excellent CIE Lab perceptual colour space dates from If you have something constructive to offer, post that instead of empty criticism.
The authoritative IEC std uses 0. And to add to the thread, the replacement method for WCAG 3. Show 3 more comments.
Community Bot 1 1 1 silver badge. That is exactly what I needed. I was doing a classic "color bars" demo, and wanted to label them on top of the color with the best black-or-white choice!
To add what all the others said: All these equations work kinda well in practice, but if you need to be very precise you have to first convert the color to linear color space apply inverse image-gamma , do the weight average of the primary colors and - if you want to display the color - take the luminance back into the monitor gamma. Nils Pipenbrinck Nils Pipenbrinck Just for the record the link is dead, archive version here - web.
HSV is not perceptually uniform and it isn't even close. It is used only as a "convenient" way to adjust color, but it is not relevant to perception, and the V does not relate to the true value of L or Y CIE Luminance.
Here's a bit of C code that should properly calculate perceived luminance. EddingtonsMonkey EddingtonsMonkey 7 7 bronze badges. H is hue which is a numerical value for the color i. S is the saturation of the color, i. Ian Hopkinson Ian Hopkinson 3, 4 4 gold badges 23 23 silver badges 28 28 bronze badges. Problem with the HSV color space is that you can have the same saturation and value, but different hue's, for blue and yellow. Yellow is much brighter than blue.
Same goes for HSL. They are useful for "controls" for adjusting relative color, but not for accurate prediction of perceptual lightness. Gandalf Gandalf.
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