reshape command debug/matrix exceeds dimensions

psz=length(pic);  
p=0  

for i=1:outs:(psz) % dividing in blocks
        for j=1:outs:(psz)

              p=p+1;

              blocks(:,:,p)=pic(i:i+outs-1,j:j+outs-1);

            %ins(:,p)=reshape(blocks(:,:,p)',1,ins')';

        end
    end

error: Index exceeds matrix dimensions.

Error in train (line 28) blocks(:,:,p)=pic(i:i+outs-1,j:j+outs-1);

is the problem at the values that variable p is allowed to take?