how to equalise the brightness of an image

Hello everybody, i have a rgb image ''cup''.

www.uploadpic.org/v.php?img=kDONT2KPu

As we see, this has a non-uniform image right side of which is brighter.

I want to make addition only left side or maybe i can subtract from right side and create a new image.

I tried this : ...

      cup=imread('cup.jpg');
      sizeofcup=size(Image1);         
      middleofcoloumn=sizeofcup(2)/2;
      NewImage= cup(:,1:middleofcoloumn)+50;

but it changes into gray and it is cropped.

how can i make it rgb and montage?

Answer 1

[Image Analyst]

You forgot that it is a color image. Try

NewImage = cup; % Initialize
New(:, 1:middleofcoloumn, :) = New(:, 1:middleofcoloumn, :) +50;