compute image to have RMS, skewness and kurtosis images

image pixel data are stored as a matrix format named "A1" (688 x 512) - grey-scale Since the data should be converted to a double precision format,

Data_d = double(A1.Data);

1. How do I compute RMS, skewness and kurtosis images?

2. Also how do i compute PDFS plots for those images?

here is a code I wrote..

 I=imread('A1');
 I2 = im2double(I);
 s=skewness(I2(:))

 figure;imagesc(s);colormap jet;colorbar;

 k = kurtosis(I2(:)

 figure;imagesc(k);colormap jet;colorbar;

figure that pop up after running a code is definitely wrong.. but I dont know why..

figure I got

figure I need to get