How to fit mask on face using facial feature points on face opencv c++ / ios ?

edit

You can easily mask upon an image using the following funciton:

def transparentOverlay(src, overlay, pos=(0, 0), scale=1):
    overlay = cv2.resize(overlay, (0, 0), fx=scale, fy=scale)
    h, w, _ = overlay.shape  # Size of foreground
    rows, cols, _ = src.shape  # Size of background Image
    y, x = pos[0], pos[1]  # Position of foreground/overlay image

    # loop over all pixels and apply the blending equation
    for i in range(h):
        for j in range(w):
            if x + i >= rows or y + j >= cols:
                continue
            alpha = float(overlay[i][j][3] / 255.0)  # read the alpha channel
            src[x + i][y + j] = alpha * overlay[i][j][:3] + (1 - alpha) * src[x + i][y + j]
    return src

You need to pass the source image, then the overlay mask and position where you want to set the mask. You can even set the masking scale. by calling it like this way.

transparentOverlay(face_cigar_roi_color,cigar,(int(w/2),int(sh_cigar/2)))

For details you can look at this link: Face masking and Overlay using OpenCV python

Output: