determining white point in the color image

Hi, I have a doubt, I need to find the white point in the color image in a particular axis say x axis ? how do I proceed about it ?

[jonas]

Example image and desired output?

[Image Analyst]

Do you think it's the brightest place, if you converted it to gray scale? And what do you mean by "in a particular axis"? Do you mean you only want to consider pixels along the very bottom row of the image?

[Malini Bakthavatchalam]

Hi Jonas I have attached the image, and i want to know how the image looks with colors from the x axis. so in x axis the color range from red to green in the transition from the reddish to green we have a midgrey or white point, i want a histogram with that mid grey point in between .

[Malini Bakthavatchalam]

@Image Analyst, I dont think i am talking about the brightest point in the image, in color point of view we have 3 axis one axis will have range of red transition to green reddish green on one side and greenish red on other in the axis, there is a point in the middle... called the white or mid grey so i want to see that point. I am looking on examples to paste it here.

[jonas]

Sorry. I still dont understand what you mean. When you refer to axes, are you talking about colorspace or the image coordinate system?

[Malini Bakthavatchalam]

the image i attached is in DKL color space to create that space i got matrix that had 3 axis, the axis displaces light dark part of the image, x axis is the red green part of the image and y is the yellow violet color range of the image. now i want to look at the x axis and the middle part where the transition goes from red2green. I will attach the code i used to create the attached color image ..

RGB = imread('originalimg.png');

MyImrgb = reshape(im2double(RGB), [],3);

Imrgb = MyImrgb.^2.2; %gamma correction

% [x, y, z] = size(Imrgb);

% ld % rg %yv

ldrgyv2rgbMat = [1,1,0.236748566577269;

1,-0.299338211934457,-0.235643322285071;

1,0.0137437185685517,1]; % B

MyImrgbCol = reshape(Imrgb * ldrgyv2rgbMat, size(RGB));

MyImldrgyvCol = reshape(reshape(MyImrgbCol, [],3) *inv(ldrgyv2rgbMat),size(MyImrgbCol));

imshow(MyImldrgyvCol)

[Malini Bakthavatchalam]

@Image Analyst the white i meant is something like this in the attached image , so using my above code i need to find the histogram of x axis

LM axis = MyImldrgyvCol(2,:)

LMhist = imhist(LM axis);

median = median(LMhist) (% so by median here i mean the white point here to be set as median) -- is this possible?

[Malini Bakthavatchalam]

@Image analyst & @Jonas http://illusionoftheyear.com/2016/06/lights-and-darks-in-vision/

This was created by my team 4 yrs ago, now I am doing the same thing in color so I need this median grey in that particular axis to know how i can rectify from the particular value .