卷积两个图像

Question

这是我编码我的图像和相同图像的16 * 16补丁的编码。我现在改变了我的编码。但是我只得到满是白色像素的图像？这是我改变的编码

clear all
close all

I=imread('E:\double.jpg');
subplot(3,2,1);
imshow(I);
title('Original');

%gray conversion
J = rgb2gray(I);
subplot(3,2,2);
imshow(J);
title('Gray');

K = double(J);

%size of the image
[A B]=size(J);
%patch definition
patch_size = 16;

        temp = J(1:patch_size, 1:patch_size);
        subplot(3,2,3);
        imshow(temp);
        title('kernel');
        temp1 = double(temp);

        C = conv2(temp1,K);
        subplot(3,2,4);       
        imshow(C);
        title('Convolved image');