使用openCV从另一个图像中减去一个图像

Question

How can I subtract one image from another using openCV?

Ps.: I coudn't use the python implementation because I'll have to do it in C++

Answer 1

#include <cv.h>
#include <highgui.h>

using namespace cv;

Mat im = imread("cameraman.tif");
Mat im2 = imread("lena.tif");

Mat diff_im = im - im2;

Change the image names. Also make sure they have the same size.

Answer 2

Use LoadImage to load your images into memory, then use the Sub method.

This link contains some example code, if that will help: http://permalink.gmane.org/gmane.comp.lib.opencv/36167

Answer 3

Instead of using diff or just plain subtraction im1-im2 I would rather suggest the OpenCV method cv::absdiff

using namespace cv;
Mat im1 = imread("image1.jpg");
Mat im2 = imread("image2.jpg");
Mat diff;
absdiff(im1, im2, diff);

Since images are usually stored using unsigned formats, the subtraction methods of @Dat and @ssh99 will kill all the negative differences. For example, if some pixel of a BMP image has value [20, 50, 30] for im1 and [70, 80, 90] for im2 , using both im1 - im2 and diff(im1, im2, diff) will produce value [0,0,0] , since 20-70 = -50 , 50-80 = -30 , 30-90 = -60 and all negative results will be converted to unsigned value of 0 , which, in most cases, is not what you want. Method absdiff will instead calculate the absolute values of all subtractions, thus producing more reasonable [50,30,60] .

Answer 4

use cv::subtract() method.

Mat img1=some_img;
Mat img2=some_img;

Mat dest;

cv::subtract(img1,img2,dest); 

This performs elementwise subtract of (img1-img2). you can find more details about it http://docs.opencv.org/modules/core/doc/operations_on_arrays.html