image masking by position

I want to analyses a part of an image without disturbing the full image. Lets say the position of the image part to be analyzed is [x1,x2,y1,y2]. i tired using the below mentioned code but was not able to do it.

I = imread('cameraman.tif'); F= image(I, [x1 y1 x2 y2]);

??? Error using ==> image Incorrect number of arguments specified

Error in ==> fd at 39 F=image(I, [x1,y1,x2,y2])

Answer 1

[Image Analyst]

You wanted (the badly-named) I, like lain said, rather than image(), which is a built-in function for displaying images and which is why you got the error you did. Also, please see the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_mask_an_image.3F

Answer 2

[Iain]

segment = I(x1:x2,y1:y2);