Visualizing depth image OpenCV

Question

This question is similar to this one, however in this image I only have a subset of pixels with a valid depth and the rest are set to zero.

For example, here is the rgb:

where all the white pixels have no depth (depth value of 0). If I use the method in the linked question, which is:

double min;
double max;
cv::minMaxIdx(map, &min, &max);
cv::Mat adjMap;
cv::convertScaleAbs(map, adjMap, 255 / max);
cv::imshow("Out", adjMap);

I get the following image, from which it is not very clear to see the depth differences:

The min and max depth values on the object are 601 and 654 respectively.

Answer 1

try subtracting the minimum first, then scale to your data range:

double min;
double max;
cv::minMaxIdx(map, &min, &max);
map -= min;
cv::Mat adjMap;
cv::convertScaleAbs(map, adjMap, 255.0 / double(max-min) );
cv::imshow("Out", adjMap);