Resolving the OpenCV Error: (-215:Assertion failed) !_map1.empty() in Image Remapping

---

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding the OpenCV Assertion Error

The Problem

In this case, the error message was triggered by the following line in the warping_image function:

[[See Video to Reveal this Text or Code Snippet]]

The root of the problem lies in the mapping arrays inter_mapx and inter_mapy, which inadvertently become empty due to incorrect indexing following resizing. Here's a snippet illustrating the problematic lines:

[[See Video to Reveal this Text or Code Snippet]]

Cause of the Error

The rewrite index [80:72] is incorrect. Because it attempts to slice the resized array (which has a shape of (80, 80)) in a manner that results in an empty array, you receive the Assertion failed error when trying to use this empty mapping for image remapping.

Step-by-Step Solution to Fix the Error

To resolve this issue, follow these steps to ensure valid indexing and correct function execution:

Step 1: Revisit the Resize Calls

Change the problematic lines that resize your mapping arrays. Instead of cutting off parts of the arrays using invalid indexing, adjust the slices properly. The original lines look like this:

[[See Video to Reveal this Text or Code Snippet]]

These should be modified to:

[[See Video to Reveal this Text or Code Snippet]]

By simply removing the invalid indexing, you retain the full resized arrays.

Step 2: Verify the Changes

Step 3: Testing

Always remember to thoroughly test your new implementation with various images and random transformations to ensure everything operates as expected without throwing errors.

Conclusion

If you continue to face challenges or have further questions, don't hesitate to reach out to the community or delve into the OpenCV documentation for more insights!