RoI Extraction Fails When Lecture Slide Fills Entire Frame
## Issue Description
This bug originates from the implementation of **extract_roi_from_image_for_slide()**, which was introduced in #1. While the function successfully isolates lecture slides in mixed-content frames, it does not handle cases where the slide fills the entire image (without additional elements like a professor, chat window, or overlays), leading to detection failures.
Because the slide covers the entire frame, there are no distinguishable edges, causing the contour extraction to not detect the slide as a rectangle.
## Steps to Reproduce
Use an image where the lecture slide completely fills the frame.
Apply the extract_roi_from_image_for_slide() function.
## Exmaple:
| **Step** | **Image** | **Description** |
|----------|-----------|-----------------|
| **Original Image (Full-Screen Slide)** | {width="1000"} | The lecture slide completely fills the frame, leaving no visible edges for detection. |
| **Canny Edge Detection Failure** | {width="1000"} | Since the slide covers the entire image, the edge detection does not find clear edges around the slide. |
| **Contour Extraction Issues** | {width="1000"} | The function fails to extract contours around the slide, because no sharp edges exist. |
| **Failed RoI Extraction** | {width="1000"} | The expected Region of Interest (RoI) is not properly identified, therefore the biggest rectangle gets choosen as the RoI, leading to incorrect extraction. |
## Expected Behavior
The algorithm should still detect the boundaries of the slide and correctly extract the Region of Interest (RoI), even if no additional elements are present in the frame.
## Actual Behavior
The Canny edge detection fails to highlight meaningful edges.
The contour extraction step does not return usable results.
The algorithm cannot determine a valid bounding rectangle for the slide.
## Potential Solutions
Use template matching to identify the slide content boundaries.
Add padding to the image to ensure the slide has visible edges.
issue