本博文用来记录使用python实现增强现实
增强现实技术，即实时地计算摄影机影像的位置及角度并加上相应图像、视频、3D模型的技术，这种技术的目标是在屏幕上把虚拟世界套在现实世界并进行互动。
主要工作：实现动态的放置虚拟模型，本文实现了在自己上传的视频中添加虚拟模型，也可以实时添加模型到视频里。
主要代码：
import argparse
import cv2
import numpy as np
import math
import os
from objloader_simple import *
# Minimum number of matches that have to be found
# to consider the recognition valid
MIN_MATCHES = 10
def main():
"""
This functions loads the target surface image,
"""
homography = None
# matrix of camera parameters (made up but works quite well for me)
camera_parameters = np.array([[800, 0, 320], [0, 800, 240], [0, 0, 1]])
# create ORB keypoint detector
orb = cv2.ORB_create()
# create BFMatcher object based on hamming distance
bf = cv2.BFMatcher(cv2.NORM_HAMMING, crossCheck=True)
# load the reference surface that will be searched in the video stream
dir_name = os.getcwd()
model = cv2.imread(os.path.join(dir_name, 'D:/Pycharm/test/book_frontal.JPG'), 0)
# Compute model keypoints and its descriptors
kp_model, des_model = orb.detectAndCompute(model, None)
# Load 3D model from OBJ file
obj = OBJ(os.path.join(dir_name, 'D:/Pycharm/test/ar/models/rat.obj'), swapyz=True) # obj model
# init video capture
# cap = cv2.VideoCapture(0) # Implementing Video Recording
cap = cv2.VideoCapture("D:/Yume/Video/zyl.mp4") # import video
while True:
# read the current frame
ret, frame = cap.read()
if not ret:
print "Unable to capture video"
return
# find and draw the keypoints of the frame
kp_frame, des_frame = orb.detectAndCompute(frame, None)
# match frame descriptors with model descriptors
matches = bf.match(des_model, des_frame)
# sort them in the order of their distance
# the lower the distance, the better the match
matches = sorted(matches, key=lambda x: x.distance)
# compute Homography if enough matches are found
if len(matches) > MIN_MATCHES:
# differenciate between source points and destination points
src_pts = np.float32([kp_model[m.queryIdx].pt for m in matches]).reshape(-1, 1, 2)
dst_pts = np.float32([kp_frame[m.trainIdx].pt for m in matches]).reshape(-1, 1, 2)
# compute Homography
homography, mask = cv2.findHomography(src_pts, dst_pts, cv2.RANSAC, 5.0)
if args.rectangle:
# Draw a rectangle that marks the found model in the frame
h, w = model.shape
pts = np.float32([[0, 0], [0, h - 1], [w - 1, h - 1], [w - 1, 0]]).reshape(-1, 1, 2)
# project corners into frame
dst = cv2.perspectiveTransform(pts, homography)
# connect them with lines
frame = cv2.polylines(frame, [np.int32(dst)], True, 255, 3, cv2.LINE_AA)
# if a valid homography matrix was found render cube on model plane
if homography is not None:
try:
# obtain 3D projection matrix from homography matrix and camera parameters
projection = projection_matrix(camera_parameters, homography)
# project cube or model
frame = render(frame, obj, projection, model, False)
#frame = render(frame, model, projection)
except:
pass
# draw first 10 matches.
if args.matches:
frame = cv2.drawMatches(model, kp_model, frame, kp_frame, matches[:10], 0, flags=2)
# show result
cv2.imshow('frame', frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
print "Not enough matches found - %d/%d" % (len(matches), MIN_MATCHES)
cap.release()
cv2.destroyAllWindows()
return 0
def render(img, obj, projection, model, color=False): # rending
"""
Render a loaded obj model into the current video frame
"""
vertices = obj.vertices
scale_matrix = np.eye(3) * 3
h, w = model.shape
for face in obj.faces:
face_vertices = face[0]
points = np.array([vertices[vertex - 1] for vertex in face_vertices])
points = np.dot(points, scale_matrix)
# render model in the middle of the reference surface. To do so,
# model points must be displaced
points = np.array([[p[0] + w / 2, p[1] + h / 2, p[2]] for p in points])
dst = cv2.perspectiveTransform(points.reshape(-2, 1, 3), projection)
imgpts = np.int32(dst)
if color is False:
cv2.fillConvexPoly(img, imgpts, (17, 37, 211))
else:
color = hex_to_rgb(face[-1])
color = color[::-1] # reverse
cv2.fillConvexPoly(img, imgpts, color)
return img
def projection_matrix(camera_parameters, homography):
"""
From the camera calibration matrix and the estimated homography
compute the 3D projection matrix
"""
# Compute rotation along the x and y axis as well as the translation
homography = homography * (-1)
rot_and_transl = np.dot(np.linalg.inv(camera_parameters), homography)
col_1 = rot_and_transl[:, 0]
col_2 = rot_and_transl[:, 1]
col_3 = rot_and_transl[:, 2]
# normalise vectors
l = math.sqrt(np.linalg.norm(col_1, 2) * np.linalg.norm(col_2, 2))
rot_1 = col_1 / l
rot_2 = col_2 / l
translation = col_3 / l
# compute the orthonormal basis
c = rot_1 + rot_2
p = np.cross(rot_1, rot_2)
d = np.cross(c, p)
rot_1 = np.dot(c / np.linalg.norm(c, 2) + d / np.linalg.norm(d, 2), 1 / math.sqrt(2))
rot_2 = np.dot(c / np.linalg.norm(c, 2) - d / np.linalg.norm(d, 2), 1 / math.sqrt(2))
rot_3 = np.cross(rot_1, rot_2)
# finally, compute the 3D projection matrix from the model to the current frame
projection = np.stack((rot_1, rot_2, rot_3, translation)).T
return np.dot(camera_parameters, projection)
def hex_to_rgb(hex_color):
"""
Helper function to convert hex strings to RGB
"""
hex_color = hex_color.lstrip('#')
h_len = len(hex_color)
return tuple(int(hex_color[i:i + h_len // 3], 16) for i in range(0, h_len, h_len // 3))
# Command line argument parsing
# NOT ALL OF THEM ARE SUPPORTED YET
parser = argparse.ArgumentParser(description='Augmented reality application')
parser.add_argument('-r','--rectangle', help = 'draw rectangle delimiting target surface on frame', action = 'store_true')
parser.add_argument('-mk','--model_keypoints', help = 'draw model keypoints', action = 'store_true')
parser.add_argument('-fk','--frame_keypoints', help = 'draw frame keypoints', action = 'store_true')
parser.add_argument('-ma','--matches', help = 'draw matches between keypoints', action = 'store_true')
# TODO jgallostraa -> add support for model specification
#parser.add_argument('-mo','--model', help = 'Specify model to be projected', action = 'store_true')
args = parser.parse_args()
if __name__ == '__main__':
main()
实现结果：
此次实验做的比较粗糙，有兴趣的朋友可以多加研究。