function ps2 (mode)

%% This is the MATLAB script for PS2.
%% By Alan Daniels
%% Note: This has some control code to slow it down.
%% Matlab chokes when you ask it to do to much.


%% Read in the original image.
[ORIG, MAP] = imread('lung.jpg', 'JPEG');
ORIG = ind2gray(ORIG, gray(256));

FILT = filter2(fspecial('gaussian', 7), ORIG);
imwrite(FILT, 'lung_filt.jpg', 'JPEG');

NOISY = imnoise(ORIG, 'gaussian', 0.12);
imwrite(NOISY, 'lung_noisy.jpg', 'JPEG');

CLEAN = filter2(fspecial('gaussian', 7), imnoise(ORIG, 'gaussian', 0.12));
imwrite(CLEAN, 'lung_clean.jpg', 'JPEG');

%% Downward gradient, 1 by 2.
%% if mode == 1
	SCALE = 10;

	GY = double(zeros(2, 1));
	GY(1, 1) =  1;
	GY(2, 1) = -1;

	II = abs(conv2(GY, ORIG));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'graddown_1x2_orig.jpg', 'JPEG');

	II = abs(conv2(GY, FILT));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'graddown_1x2_filt.jpg', 'JPEG');

	II = abs(conv2(GY, NOISY));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'graddown_1x2_noisy.jpg', 'JPEG');

	II = abs(conv2(GY, CLEAN));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'graddown_1x2_clean.jpg', 'JPEG');
%% end


%% Downward gradient, 2 by 2.
%% if mode == 2
	SCALE = 10;

	GY = double(zeros(2, 2));
	GY(1, 1:2) = [ 1  1];
	GY(2, 1:2) = [-1 -1];

	II = abs(conv2(GY, ORIG));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'graddown_2x2_orig.jpg', 'JPEG');

	II = abs(conv2(GY, FILT));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'graddown_2x2_filt.jpg', 'JPEG');

	II = abs(conv2(GY, NOISY));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'graddown_2x2_noisy.jpg', 'JPEG');

	II = abs(conv2(GY, CLEAN));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'graddown_2x2_clean.jpg', 'JPEG');
    %end


%% Rightward gradient, 1 by 2.
%% if mode == 3
	SCALE = 10;

	GX = double(zeros(2, 1));
	GX(1, 1:2) = [1 -1];

	II = abs(conv2(GX, ORIG));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'gradright_1x2_orig.jpg', 'JPEG');

	II = abs(conv2(GX, FILT));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'gradright_1x2_filt.jpg', 'JPEG');

	II = abs(conv2(GX, NOISY));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'gradright_1x2_noisy.jpg', 'JPEG');

	II = abs(conv2(GX, CLEAN));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'gradright_1x2_clean.jpg', 'JPEG');
    %end


%% Rightward gradient, 2 by 2.
%% if mode == 4
	SCALE = 10;

	GX = double(zeros(2, 2));
	GX(1, 1:2) = [1 -1];
	GX(2, 1:2) = [1 -1];

	II = abs(conv2(GX, ORIG));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'gradright_2x2_orig.jpg', 'JPEG');

	II = abs(conv2(GX, FILT));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'gradright_2x2_filt.jpg', 'JPEG');

	II = abs(conv2(GX, NOISY));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'gradright_2x2_noisy.jpg', 'JPEG');

	II = abs(conv2(GX, CLEAN));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'gradright_2x2_clean.jpg', 'JPEG');
    %end



%% Roberts operator.
%% if mode == 5
	SCALE = 5;

	GX = double(zeros(2, 2));
	GX(1, 1:2) = [1  0];
	GX(2, 1:2) = [0 -1];
 
	GY = double(zeros(2, 2));
	GY(1, 1:2) = [0 -1];
	GY(2, 1:2) = [1  0];

	II = abs(conv2(GX, ORIG)) + abs(conv2(GY, ORIG));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'roberts_orig.jpg', 'JPEG');

	II = abs(conv2(GX, FILT)) + abs(conv2(GY, FILT));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'roberts_filt.jpg', 'JPEG');

	II = abs(conv2(GX, NOISY)) + abs(conv2(GY, NOISY));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'roberts_noisy.jpg', 'JPEG');

	II = abs(conv2(GX, CLEAN)) + abs(conv2(GY, CLEAN));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'roberts_clean.jpg', 'JPEG');
    %end


%% Sobel operator.
%% if mode == 6
	SCALE = 5;

	GX = double(zeros(3, 3));
	GX(1, 1:3) = [-1 0 1];
	GX(2, 1:3) = [-2 0 2];
	GX(3, 1:3) = [-1 0 1];

	GY = double(zeros(3, 3));
	GY(1, 1:3) = [ 1  2  1];
	GY(2, 1:3) = [ 0  0  0];
	GY(3, 1:3) = [-1 -2 -1];

	II = abs(conv2(GX, ORIG)) + abs(conv2(GY, ORIG));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'sobel_orig.jpg', 'JPEG');

	II = abs(conv2(GX, FILT)) + abs(conv2(GY, FILT));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'sobel_filt.jpg', 'JPEG');

	II = abs(conv2(GX, NOISY)) + abs(conv2(GY, NOISY));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'sobel_noisy.jpg', 'JPEG');

	II = abs(conv2(GX, CLEAN)) + abs(conv2(GY, CLEAN));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'sobel_clean.jpg', 'JPEG');
    %end



%% Prewitt operator.
%% if mode == 7
	SCALE = 5;

	GX = double(zeros(3, 3));
	GX(1, 1:3) = [-1 0 1];
	GX(2, 1:3) = [-1 0 1];
	GX(3, 1:3) = [-1 0 1];

	GY = double(zeros(3, 3));
	GY(1, 1:3) = [ 1  1  1];
	GY(2, 1:3) = [ 0  0  0];
	GY(3, 1:3) = [-1 -1 -1];

	II = abs(conv2(GX, ORIG)) + abs(conv2(GY, ORIG));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'prewitt_orig.jpg', 'JPEG');

	II = abs(conv2(GX, FILT)) + abs(conv2(GY, FILT));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'prewitt_filt.jpg', 'JPEG');

	II = abs(conv2(GX, NOISY)) + abs(conv2(GY, NOISY));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'prewitt_noisy.jpg', 'JPEG');

	II = abs(conv2(GX, CLEAN)) + abs(conv2(GY, CLEAN));
	II = II * SCALE; clip(II);
	imshow(II); imwrite(II, 'prewitt_clean.jpg', 'JPEG');
%% end