How do you change pixels in an image?

i want to get the difference between two pixel and then i want to chang pixel value to become yellow . please help!!!!

Answer 1

[Jan]

The question is not clear. Are you talking about RGB images? Which pixel should be set to yellow? Perhaps this helps:

image1 = rand(100,100,3);
image2 = rand(100,100,3);
diffPixel = image1(51,67,:) - image2(51,67,:);
image1(51,67,:) = [1, 1, 0];

[Isee You]

i work in gray image (2d) and i want to to get the difference between two pixel and if the difference is small than Specific number . I colored a pixel yellow(any pixel i want)

[Image Analyst]

Try this first: http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

Then come back and tell us which two pixels you want to take the difference of and which pixels you want to set to yellow. Do you want to convert your gray scale image to RGB color now? Or do you want to apply a colormap? Do you have any photos that you uploaded to tinypic.com that you can show us? You need to put some work into your question, more than 10 seconds anyway. Because as I see it, Jan has answered your question. If not, you need to explain why.

[Isee You]

any help

Answer 2

[Isee You]

OK i will try as possible. my project is locate dark part in this image and isolate it

http://www.mediafire.com/i/?g17fhg01c700h7u

i read this sheet

http://www.mediafire.com/?5b2pyo2m1qr2pkl

you can see in page (5) figure (a) the algorithm i work in . This algorithm is so close to this http://www.mathworks.com/matlabcentral/answers/26697-how-to-calculate-gradient-between-the-currently-processed-point-x-y-and-its-neighboring-point-in-o

ok.

[Image Analyst]

Do you mean the dark part between the outer body wall and the internal organs?

[Isee You]

no the small dark part inside the liver .

[Image Analyst]

Give us some code to start with. I don't want to develop the whole app from scratch for you.

Answer 3

[Isee You]

i isolate the liver and then i use this code to get the difference between the pixels (x.jpg)is my image of liver only.

function test4_loop(img) 
  a = imread('x,jpg');

    [xx,yy]=size(a);
    for x=1:(xx-3)
     for y=1:(yy-3)
        z1=impixel (a,x,y)
        z2=impixel (a,x,(y+1));
        z3=impixel (a,x,(y+2));
        z4=impixel (a,(x+1),(y));
        z5=impixel (a,(x+1),(y+1));
        z6=impixel (a,(x+1),(y+2));
        z7=impixel (a,(x+2),(y));
        z8=impixel (a,(x+2),(y+1));
        z9=impixel (a,(x+2),(y+2));
        z=[z1 z2 z3;
      z4 z5 z6;
      z7 z8 z9];
    avg=mean2(z);
      do(avg,x,y);
     end   

    end

function do(mean,x,y)
a=imread('x.jpg');
%north eset
while x>0 && y>0
    r=mean-a(x-1,y-1);
    x=x-1;
    y=y-1;
end
%north
while x>0 && y>0
    r=mean-a(x-1,y+1);
    x=x-1;
end
%north west
while x>0 && y>0
    r=mean-a(x-1,y+2);
    x=x-1;
    y=y+1;
end
%west
while x>0 && y>0
    r=mean-a(x+1,y+3);
    y=y+1;
end
%north west
while x>0 && y>0
    r=mean-a(x+3,y+3);
    x=x+1;
    y=y+1;
end
%norht
while x>0 && y>0
    r=mean-a(x+3,y+1);
    x=x-1;
    y=y-1;
end
%north east
while x>0 && y>0
    r=mean-a(x+3,y-1);
    x=x+1;
    y=y-1;
end
%eset
while x>0 && y>0
    r=mean-a(x+1,y-1);
      y=y-1;
end

you can see this file to understand what i mean about (x,y)

http://www.mediafire.com/?el5535xp5q3eg8l

[Isee You]

any help