How to "zero" everything within a masked part of an image in OpenCV

c++ opencv mask
Jackson Dean Goodwin picture Jackson Dean Goodwin · Jul 10, 2012 · Viewed 33.1k times · Source

If I have an image (IplImage 8-bit) and a binary mask (which is also an 8-bit IplImage of the same size, where every pixel has a value of either 0 or 255), how can I make every pixel in the image that corresponds with a pixel in the mask with a value of zero have a value of zero, and every pixel in the image that corresponds with a pixel in the mask with any other value (namely 255) have the same value as in the original image?

In other words, anything that is "in the mask area" will keep its original value, and anything outside the mask area will become zero.

Answer

Antonio Sesto picture Antonio Sesto · Jan 30, 2013

Simplest way, with 'Mat img' (image to be masked, input) and 'Mat masked' (masked image, output):

  img.copyTo(masked, mask)

where 'Mat mask' is a matrix not necessarily binary (copyTo considers elements with zero value). Masked can be of any size and type; it is reallocated if needed.

See the doc.

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