How do I get a count of all the pixels having a certain RGB value in an image?

I have a black and white image with a green arrow. I need a count of all the green pixels alone from the image. OR, I need a way to select just the green pixels in order to measure the length and midpoint of the arrow. Can someone help?

gcount=0;
for i=1:width
  for j=1:height
% this gives me just the green channel and the ans is incorrect since the rest of my image is black and white
% if I(i,j,1)==0 & I(i,j,2)==255 & I(i,j,3)==0
if impixel(I,i,j)= =[0 255 0] %this logic is correct but takes way too long
      gcount=gcount+1;
      end
  end
end

Answer 1

[Walter Roberson]

sum(sum(YourImage(:,:,1) == 0 & YourImage(:,:,2) == 255 & YourImage(:,:,3) == 0))

[Coder Bee]

Thank you so much. It worked perfectly.

[Coder Bee]

Do you have any idea how to store these pixel values in an array. I need to calculate the mid point of this green arrow based on this.

[Walter Roberson]

mask = YourImage(:,:,1) == 0 & YourImage(:,:,2) == 255 & YourImage(:,:,3) == 0;

Now you can calculate the centroid of mask

Answer 2

[Image Analyst]

There is something called the "color frequency image" and the code is here http://www.mathworks.com/matlabcentral/fileexchange/28164-color-frequency-image

You can also do color segmentation using demos from my File Exchange and compute pixel count or area fraction. http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862

[Coder Bee]

Thank you for your help.