vision utils

Various utilities for OpenCV.

Documentation

class FPSCounter: utility for measuring frames per second (FPS) with a rolling average
- FPSCounter(avg_len=30): create a new FPS counter that averages avg_len measurements
- got_frame(): tell the counter that a frame was processed
- fps(): get the average FPS
- draw_fps(self, img, pos=(10,30), prec=1, size=2, thickness=2, color=(255,255,255), fmt='%.1f FPS'): draw the FPS on an image
  - img: the image to draw on
  - pos: the position to draw the text at
  - prec: the number of decimal digits to display
  - size: the size of the text
  - thickness: the thickness of the text
  - color: the color of the text
  - fmt: the format string for the text. Must format a float.

Color-related utilities

hex2bgr(h): converts a hexadecimal color into a BGR numpy array. E.g. 0x00FF01 -> [1, 255, 0]
cvtPixel(color, code): converts a color into another color space.
- color: the color to convert. Can be a list, numpy array, or tuple – e.g. (255, 0, 0)
- code: an OpenCV color conversion code, e.g. cv2.COLOR_HSV2BGR
Color constants (in BGR): MAROON, RED, ORANGE, YELLOW, OLIVE, GREEN, PURPLE, FUCHSIA, LIME, TEAL, AQUA, BLUE, NAVY, BLACK, GRAY, SILVER, WHITE.

sort_contour(contour): sorts a contour's points in clockwise order.
- contour: a numpy array of points with shape (n_points, 1, 2)
center(contour): returns the center of a contour as tuple (cx, cy)
iou(contour1, contour2): returns the intersection over union (IOU) of two contours. IOU = (area of intersection) / (area of union)