OpenCV: Threshold and Invert an image

c++ opencv cinder
Sr.Richie picture Sr.Richie · Oct 1, 2014 · Viewed 32.9k times · Source

I'm trying to threshold and invert an image with Cinder OpenCV block. In openFrameworks I would use something like that:

someImage.threshold(230, true);

...where true is the parameter to specify to threshold and invert.

In Cinder I'm trying the following:

cv::threshold (input, threshNear, 230, 255, CV_THRESH_BINARY_INV);

... that doesn't work, or

cv::threshold (input, threshNear, 100, 255, CV_8U);
cv::invert ( threshNear,  threshNearInverted);

...that produces and error and let the program stuck.

Any suggestion?

Answer

Sr.Richie picture Sr.Richie · Oct 1, 2014

Ok, after more testing I've realized that actually the way to go is 

 cv::threshold (input, threshNear, 70, 255, CV_THRESH_BINARY_INV);

the problem with the code I posted in my question looks like to be related with the threshold value I was trying to use (230 on 255). If I use a lower value (like for example 70 on 255) the color inversion actually works.

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