Re: adjust color
Posted by
Michael Schmid on
Jul 27, 2015; 4:10pm
URL: http://imagej.273.s1.nabble.com/adjust-color-tp5013718p5013766.html
On Jul 23, 2015, at 12:31, Paweł Łabno wrote:
> my selection is for example rgb 185,115, 64
> i'd like whole image to adjust so this selection becomes rgb (160, 105,120)
> how can i do that?
Hi Pawel,
there was already a reply to a recent mail of yours on the same subject:
https://list.nih.gov/cgi-bin/wa.exe?A2=ind1507&L=IMAGEJ&F=&S=&P=88920It really depends a lot on how you want to adjust the image:
(1) If the white balance of the camera or the illumination has changed, an approximate way would be multiplying each pixel with an appropriate value.
(2) If the background is not black any more, e.g. due to stray light, you have to subtract the 'black' pixel values from all pixels. Not that this works only if the response of the camera is linear. If your camera creates a JPG file, you can be sure that it is nonlinear (e.g. sRGB) and you must not add to or subtract values to get a meaningful result.
https://en.wikipedia.org/wiki/SRGB https://en.wikipedia.org/wiki/Gamma_correctionAssuming (1), convert your image to an RGB stack; multiply each channel by a suitable value (e.g. channel R should be multiplied by 160/185 = 0.86486) and convert it back to RGB.
Probably you will want to have a macro for it. If you do it manually and have the Macro Recorder active (Plugins>Macros>Record), you will find all commands except for the setSlice() command used to switch between the R, G, B channels.
http://rsb.info.nih.gov/ij/developer/macro/functions.html#setSliceHave a look at these pages for macro programming
http://rsb.info.nih.gov/ij/developer/macro/macros.html http://rsb.info.nih.gov/ij/developer/macro/functions.html http://fiji.sc/Introduction_into_Macro_ProgrammingMichael
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