Posted by
Joachim Wesner on
Aug 12, 2009; 8:20am
URL: http://imagej.273.s1.nabble.com/measuring-color-in-ImageJ-tp3691452p3691454.html
Hi Melissa,
as far as I can see, the kind of calibration you are refering too in the
link is not about colors at all!
(I.e. about defining what combination of RGB values represent "true gray")
That calibration in the link is about compensating nonlinear detector
behaviour (i.e. a double light intensity
does not read as twice the number) Yes, it will alos not change the image,
but when you read out the pixels
with the cursor, an extra number in brackets should appear that indicates
the calibrated intensity.
What about this plugin ??
http://imagejdocu.tudor.lu/doku.php?id=plugin:color:chart_white_balance:startor Landinis "Color Correct" plugin on that page:
http://www.dentistry.bham.ac.uk/landinig/software/software.htmlCheers
Mit freundlichen Grüßen / Best regards
Joachim Wesner
Melissa Amarello
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12.08.2009 03:07
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Hi,
I am a graduate student studying coloration in a rattlesnake (or I
hope to). I would like to use ImageJ, with a standardized color card
(X-Rite ColorChecker Card) to estimate reflectance in digital photos.
I have tried using the calibrate function following instructions here:
http://imagejdocu.tudor.lu/doku.php?id=gui:analyze:calibrateIn greater detail:
I open my jpg image in IJ, which contains the snake whose
color/reflectance I want to measure and the color card
I select an area within each grayscale step on the color card and use
the measure tool to record mean gray values
In "Analyze - Calibrate", I enter the actual mean gray values in the
right column (corresponding to the measured values on the left)
I pick a function (usually polynomial) and click ok.
However, after accepting the calibration function, the image does not
seem to have changed? I use the color picker to measure color in the
color card and it still says the original, incorrect gray values.
What am I doing wrong? Is there a better tutorial for the calibrate
function than the one linked above? Can I use ImageJ to calibrate a
color photo?
thanks,
melissa
Melissa Amarello
National Science Foundation Fellow
Arizona State University (Fall 2009)
http://www.public.asu.edu/~mamarell______________________________________________________________________
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