I'm using OpenCV 3.0.0 and Python 3.4.3 to process a very large RGB image (107162,79553,3). While I'm trying to resize it using the following code:
import cv2
image = cv2.resize(img, (0,0), fx=0.5, fy=0.5, interpolation=cv2.INTER_AREA)
I had this error message coming up:
cv2.error: C:\opencv-3.0.0\source\modules\imgproc\src\imgwarp.cpp:3208: error: (-215) ssize.area() > 0 in function cv::resize
I'm certain there is image content in the image array because I can save them into small tiles in jpg format. When I try to resize just a small part of the image, there is no problem and I end up with correctly resized image. (Taking a rather big chunk (50000,50000,3) still won't work, but it will work on a (10000,10000,3) chunk)
What could cause this problem and how can I solve this?
So it turns out that the problem comes from one line in modules\imgproc\src\imgwarp.cpp:
CV_Assert( ssize.area() > 0 );
When the product of rows and columns of the image to be resized is larger than 2^31, ssize.area() results in a negative number. This appears to be a bug in OpenCV and hopefully will be fixed in the future release. A temporary fix is to build OpenCV with this line commented out. While not ideal, it works for me.
And I just recently found out that the above applies only to image whose width is larger than height. For images with height larger than width, it's the following line that causes error:
CV_Assert( dsize.area() > 0 );
So this has to be commented out as well.