Image super resolution enhancement

close all;
clear all;
I=imread('1.jpeg')
I2 = im2double(I)
I2 = im2double(I,'indexed')
figure,imshow(I);

av=fspecial('average',[2 2]);
avimg=filter2(av,I2);
I1=avimg(1:2:end,1:2:end);

figure,imshow(uint8(I1));

But I am getting this error sir

Undefined function 'conv2' for input arguments of type 'double' and attributes 'full 3d real'.

Error in filter2 (line 59)
        y = conv2(hcol, hrow, x, shape);

avimg=filter2(av,I2);

Answer 1

[Walter Roberson]

JPEG images are never ever indexed images, so your second im2double() is wrong.

They are, however, almost always RGB images, so they are 3D arrays. And conv2 is not defined for 3D arrays. You can conv2 one color pane at a time though.

Answer 2

[Image Analyst]

Try imfilter() instead. It can filter color images.