What's the problem here?

I just wanted to do some simple edge detection with this code. But I get error:

"MAP must be a m x 3 array. Use im2gray for RGB and grayscale images."

I tried the im2gray function and it didn't work any better

pic = imread('good_day.jpg'); 
gray_pic = im2gray('good_day.jpg'); 
BW1 = edge(gray_pic,'Canny');
BW2 = edge(gray_pic,'Prewitt');
imshowpair(BW1,BW2,'montage');

Answer 1

[Simon Chan]

function im2gray does not accept the jpg image, it accepts the image in pixel values

Try the following:

pic = imread('good_day.jpg'); 
gray_pic = im2gray(pic);