Thermal image processing on matlab

I want to process an image in matlab and the steps are: 1-upload the image and view the pixel matrix. 2-Raise the value of the image to the power of 2. 3-The obtained values are transformed to vectors.(To find a threshold value for image binarization where gradient starts of neighboring pixels increase). 4-To obtain the index of a pixel, I use this equation P=(n/(i2-i1))* ∑grad(i). Summation for i1 to i2. i1:.1% of total length of pixel indices. i2:10% of total length of pixel indices.

How do i implement this on Matlab. Please be specific and i'm in a great need.Thanks