How to convert two rgb images into grayscale? and then subtract ?

I have two images in jpg format(one as reference image and other is captured image) . I want to convert them to grayscale and want to subtract them. How to do this?

Thanks in Advance.

[swati mane]

Thank you Very much !!!

[Jan]

@swati mane: Does this comment concern my answer? Is your problem solved?

[swati mane]

Hello sir,

My problem resolved. thank you!!!

Answer 1

[Jan]

img1 = imread('Image1.jpg');
img2 = imread('Image2.jpg');
D    = rgb2gray(img1) - rgb2gray(img2)

[Hamza Mahmood]

thank u so much

Answer 2

[Image Analyst]

If you don't want negative numbers clipped to zero you can cast to double before subtracting

image1 = imread('Image1.jpg');
image2 = imread('Image2.jpg');
diffImage  = double(rgb2gray(image1)) - double(rgb2gray(image2));
imshow(diffImage, []); % Make sure you use []

If you just want the absolute value of the difference, use imabsdiff():

diffImage = imabsdiff(image1, image2);

No need to cast to double in that case.