error using imsubtract

I've been using imsubtract, i want to replace the background with black, but why that appear only in black ... no image object .. what is wrong ...?

Answer 1

[Alex Taylor]

Megah,

I'd also recommend that you use the MATLAB minus operator instead of imsubtract to perform elementwise subtraction on two images:

image3 = im2double(image1) - im2double(image2)

The imadd and imsubtract functions are old and predate support for integer math in base MATLAB.

The MATLAB math operators are better maintained and in general will exhibit better performance:

>> a = rand(4000,4000); >> b = rand(4000,4000);

>> tic; for i = 1:100; imsubtract(a,b); end; toc

Elapsed time is 17.827151 seconds.

>> tic; for i = 1:100; a-b; end; toc

Elapsed time is 8.206314 seconds.

- Alex.

Answer 2

[Wolfgang Schwanghart]

Hi Megah, apparently both variables don't have the same class. Try

image3 = imsubtract(im2double(image1),im2double(BWfinal))

[edited according to WRs suggestion]

[Walter Roberson]

I would suggest that it would make more sense to use im2double() instead of double(), so that the values get rescaled to the [0,1] range for both images, instead of the subtraction results varying widely according to which class each of the images happened to be.

[Wolfgang Schwanghart]

Again, I have learned something new. Thanks, Walter.

[Megah Putri]

thank you wolfgang schwanghart,,, ^_^ ,,, thank you walter roberson ^_^

Answer 3

[Pramod Bhat]

convert them to the same class. both the images shud be in the same format.