ConvexHull | Convex Hull algorithm implemented in C | Computer Vision library

Your shapely polygon is not a hull figure (it is not even convex), so unsurprisingly its area is lower:

You can use the hull equations do determine if the point is inside the hull

In your program/function you are sorting the points, then you calculate the indices along with the hull. And you return the indices (based on the sorted vector). You then apply the indices to the vector, which is not sorted.

Remember, C++ can pass by reference or value/copy (I am a bit vague maybe but I hope you get the idea; if you have no idea what I am talking about then that is a topic you have to learn about).

What you can do in the second program is: sort the vector before you print it. Maybe that will give you the expected result.

A better solution takes a bit more effort: Pass by reference

If you are sure that all the original points already lie on the convex hull, you can order them via the angle their coordinates make versus their center:

No, you are not allowed to change *n since it's a const int. You need to make it non-const for it to work:

This worked:

Applying pinch and bulge distortion along facial landmarks in small amounts around eyes and nose could probably provide decent results without moving into another method. Though there is a chance it will also noticeably distort eyeglasses if it affects a larger area. These should help,

• Pinch/bulge distortion using Python OpenCV
• Image Warping - Bulge Effect Algorithm
• https://math.stackexchange.com/questions/266250/explanation-of-this-image-warping-bulge-filter-algorithm
• Formulas for Barrel/Pincushion distortion

I am not sure how to do this in opencv alone without face looking unnatural. Below is a general explanation based on my own exploration. Feel free to correct me if anything if I made any mistake.

One way I think current face beautification methods such as those on Android cameras work is to align a 3d face mesh or a whole head model on top of original face.

It extracts face texture using using facial landmarks and aligns them with corresponding 3d mesh with texture applied to it. This way the 3d mesh can be adjusted and texture will follow face geometry. There are probably additional steps such as passing the result to another network, post-processing involved to make it look more natural.

Mediapipe Face Mesh will probably be helpful also as it provides dense 3d face landmarks with 3D face models, UV visualization, coordinates. This is a discussion for UV unwrapping of face in mediapipe.

Another way is to use GANs to edit facial features, apply lighting, makeup etc.

I looked at your code, and I think problem is in sscanf, and solution is actually simple. Try to change declaration of string ( char array ) in main function from char c[5]; to char c[10]; it can be any other number, but I think, if you enter even bigger numbers and c[10] will make error, so I recommend you to make it char c[50]; or because you're using integers I think char c[25]; will be fine.

I presume you are using a latest version of OpenCV. If you are using something like 4.x.x, try the following code.