#!/usr/bin/env python

import numpy as np
import cv2
import video


def draw_flow(img, flow, step=16):
    h, w = img.shape[:2]
    y, x = np.mgrid[step/2:h:step, step/2:w:step].reshape(2,-1)
    fx, fy = flow[y,x].T
    lines = np.vstack([x, y, x+fx, y+fy]).T.reshape(-1, 2, 2)
    lines = np.int32(lines + 0.5)
    vis = cv2.cvtColor(img, cv2.COLOR_GRAY2BGR)

    cv2.polylines(vis, lines, 0, (0, 0, 0))
    # for (x1, y1), (x2, y2) in lines:
    #     cv2.circle(vis, (x1, y1), 1, (0, 255, 0), -1)
    return vis

def draw_hsv(flow):
    h, w = flow.shape[:2]
    fx, fy = flow[:,:,0], flow[:,:,1]
    ang = np.arctan2(fy, fx) + np.pi
    v = np.sqrt(fx*fx+fy*fy)

    # hsv = np.zeros((h, w, 3), np.uint8)
    # hsv[...,0] = ang*(180/np.pi/2)
    # hsv[...,1] = 255
    # hsv[...,2] = np.minimum(v*4, 255)
    # bgr = cv2.cvtColor(hsv, cv2.COLOR_HSV2BGR)

    f = np.zeros((h, w, 3), np.uint8)
    f[...,0] = 0 #np.minimum(v*10, 255)

    f[...,1] = 0
    f[...,2] = 255- np.minimum(v**2, 255) #ang*(180/np.pi/2)
    bgr = cv2.cvtColor(f, cv2.COLOR_HSV2BGR)

    return bgr

width, height = 640, 480
cam = video.create_capture("0:size="+str(width)+"x"+str(height))

while True:
    ret, prev = cam.read()
    prevgray = cv2.cvtColor(prev, cv2.COLOR_BGR2GRAY)
    if prevgray.shape == (height, width):
        break

while True:
    ret, img = cam.read()
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    print prevgray.shape, gray.shape
    flow = cv2.calcOpticalFlowFarneback(prevgray, gray, 0.5, 3, 15, 3, 5, 1.2, 0)
    prevgray = gray

    # cv2.imshow('flow', draw_flow(gray, flow))
    cv2.imshow('flow', draw_hsv(flow))

    ch = 0xFF & cv2.waitKey(5)
    if ch == 27:
        break
cv2.destroyAllWindows()