Question

Is it possible to place an image inside an image with OpenCv (JavaCv).
For example i have a 1000×1000 image and a 100×100 image. And at position 600×600 i would like to place the smaller image inside the larger image.

lets say the blue box is the 1000×1000 IplImage and the red one is the 100×100 IplImage.
Is it possible to put the red box in the blue box. Preferably computational rather efficient because it has to work in real time.

Thx in advance

Answer 1

This is in Python, but conversion to Java is going to be real easy. Use GetSubRect(), and Copy(). GetSubRect() returns a rectangular subarray of interest (specify top left point of interest, and the width and height). Then just copy over the image using Copy().

import cv
blue = cv.LoadImage("blue.jpg")
red = cv.LoadImage("red.jpg")

sub = cv.GetSubRect(blue, (100, 100, 50, 50))
cv.Copy(red,sub)

cv.ShowImage('blue_red', blue)
cv.WaitKey(0)

Alternatively, as karlphillip suggests you could specify the ‘region of interest’ using SetImageROI(), and do much the same thing:

cv.SetImageROI(blue,(100,100,50,50))
cv.Copy(red, blue)
cv.ResetImageROI(blue)

Its very important to reset the ROI, ResetImageROI, otherwise you will only display/save the ROI, and not the whole image.

Demo output:

blue: red: combined: