Question

I’m using OpenCV for object detection and one of the operations I would like to be able to perform is a per-pixel square root. I imagine the loop would be something like:

IplImage* img_;
...
for (int y = 0; y < img_->height; y++) {
  for(int x = 0; x < img_->width; x++) {
    // Take pixel square root here
  }
}

My question is how can I access the pixel value at coordinates (x, y) in an IplImage object?

Answer 1

Assuming img_ is of type IplImage, and assuming 16 bit unsigned integer data, I would say

unsigned short pixel_value = ((unsigned short *)&(img_->imageData[img_->widthStep * y]))[x];

See also here for IplImage definition.