Ask Your Question

Simple matrix operation not working : is it normal ?

asked 2014-11-23 04:42:51 -0500

huehuehue gravatar image

If I write for example image=255*image, the value of image is not updated (I should get a full white image). Is this normal ? Do I have to go through inner loops to multiply each element ?

edit retag flag offensive close merge delete

2 answers

Sort by ยป oldest newest most voted

answered 2014-11-24 03:00:39 -0500

What is the datatype of your matrix? (If you want it to be white, a image.setTo(255) for an CV_8UC1-image does the job)

Have you maybe passed your image by value instead of reference?

edit flag offensive delete link more


the image come from image = imread(argv[1], CV_LOAD_IMAGE_GRAYSCALE); So it should be CV_8UC1. I don't want the image to be white, it was just for testing the multiplication. What do you mean by passing by value instead of reference ? Normally it should be automatically be passed by reference, no ?

huehuehue gravatar imagehuehuehue ( 2014-11-27 06:48:00 -0500 )edit

Sorry I found the error. It was very stupid. My image is binary so a multiplication by 255 doesn't change anything (blacks pixels are 0's so remain black). I don't have an issue anymore.

huehuehue gravatar imagehuehuehue ( 2014-11-27 06:50:39 -0500 )edit

answered 2014-11-23 12:10:19 -0500


there is probably something wrong with your code, because this works for me... Can you post the code you use?

edit flag offensive delete link more
Login/Signup to Answer

Question Tools


Asked: 2014-11-23 04:42:51 -0500

Seen: 68 times

Last updated: Nov 24 '14