video.py OpenCv例程阅读

  1 #!/usr/bin/env python
  2 
  3 '''
  4 Video capture sample.
  5 
  6 Sample shows how VideoCapture class can be used to acquire video
  7 frames from a camera of a movie file. Also the sample provides
  8 an example of procedural video generation by an object, mimicking
  9 the VideoCapture interface (see Chess class).
 10 
 11 'create_capture' is a convinience function for capture creation,
 12 falling back to procedural video in case of error.
 13 
 14 Usage:
 15     video.py [--shotdir <shot path>] [source0] [source1] ...'
 16 
 17     sourceN is an
 18      - integer number for camera capture
 19      - name of video file
 20      - synth:<params> for procedural video
 21 
 22 Synth examples:
 23     synth:bg=../cpp/lena.jpg:noise=0.1
 24     synth:class=chess:bg=../cpp/lena.jpg:noise=0.1:size=640x480
 25 
 26 Keys:
 27     ESC    - exit
 28     SPACE  - save current frame to <shot path> directory
 29 
 30 '''
 31 
 32 import numpy as np
 33 import cv2
 34 from time import clock
 35 from numpy import pi, sin, cos
 36 import common
 37 
 38 class VideoSynthBase(object):
 39     def __init__(self, size=None, noise=0.0, bg = None, **params):
 40         self.bg = None
 41         self.frame_size = (640, 480)
 42         if bg is not None:
 43             self.bg = cv2.imread(bg, 1)
 44             h, w = self.bg.shape[:2]
 45             self.frame_size = (w, h)
 46 
 47         if size is not None:
 48             w, h = map(int, size.split('x'))
 49             self.frame_size = (w, h)
 50             self.bg = cv2.resize(self.bg, self.frame_size)
 51 
 52         self.noise = float(noise)
 53 
 54     def render(self, dst):
 55         pass
 56 
 57     def read(self, dst=None):
 58         w, h = self.frame_size
 59 
 60         if self.bg is None:
 61             buf = np.zeros((h, w, 3), np.uint8)
 62         else:
 63             buf = self.bg.copy()
 64 
 65         self.render(buf)
 66 
 67         if self.noise > 0.0:
 68             noise = np.zeros((h, w, 3), np.int8)
 69             cv2.randn(noise, np.zeros(3), np.ones(3)*255*self.noise)
 70             buf = cv2.add(buf, noise, dtype=cv2.CV_8UC3)
 71         return True, buf
 72 
 73     def isOpened(self):
 74         return True
 75 
 76 class Chess(VideoSynthBase):
 77     def __init__(self, **kw):
 78         super(Chess, self).__init__(**kw)
 79 
 80         w, h = self.frame_size
 81 
 82         self.grid_size = sx, sy = 10, 7
 83         white_quads = []
 84         black_quads = []
 85         for i, j in np.ndindex(sy, sx):
 86             q = [[j, i, 0], [j+1, i, 0], [j+1, i+1, 0], [j, i+1, 0]]
 87             [white_quads, black_quads][(i + j) % 2].append(q)
 88         self.white_quads = np.float32(white_quads)
 89         self.black_quads = np.float32(black_quads)
 90 
 91         fx = 0.9
 92         self.K = np.float64([[fx*w, 0, 0.5*(w-1)],
 93                         [0, fx*w, 0.5*(h-1)],
 94                         [0.0,0.0,      1.0]])
 95 
 96         self.dist_coef = np.float64([-0.2, 0.1, 0, 0])
 97         self.t = 0
 98 
 99     def draw_quads(self, img, quads, color = (0, 255, 0)):
100         img_quads = cv2.projectPoints(quads.reshape(-1, 3), self.rvec, self.tvec, self.K, self.dist_coef) [0]
101         img_quads.shape = quads.shape[:2] + (2,)
102         for q in img_quads:
103             cv2.fillConvexPoly(img, np.int32(q*4), color, cv2.CV_AA, shift=2)
104 
105     def render(self, dst):
106         t = self.t
107         self.t += 1.0/30.0
108 
109         sx, sy = self.grid_size
110         center = np.array([0.5*sx, 0.5*sy, 0.0])
111         phi = pi/3 + sin(t*3)*pi/8
112         c, s = cos(phi), sin(phi)
113         ofs = np.array([sin(1.2*t), cos(1.8*t), 0]) * sx * 0.2
114         eye_pos = center + np.array([cos(t)*c, sin(t)*c, s]) * 15.0 + ofs
115         target_pos = center + ofs
116 
117         R, self.tvec = common.lookat(eye_pos, target_pos)
118         self.rvec = common.mtx2rvec(R)
119 
120         self.draw_quads(dst, self.white_quads, (245, 245, 245))
121         self.draw_quads(dst, self.black_quads, (10, 10, 10))
122 
123 
124 classes = dict(chess=Chess)
125 
126 presets = dict(
127     empty = 'synth:',
128     lena = 'synth:bg=../cpp/lena.jpg:noise=0.1',
129     chess = 'synth:class=chess:bg=../cpp/lena.jpg:noise=0.1:size=640x480'
130 )
131 
132 
133 def create_capture(source = 0, fallback = presets['chess']):
134     '''source: <int> or '<int>|<filename>|synth [:<param_name>=<value> [:...]]'
135     '''
136     source = str(source).strip()
137     chunks = source.split(':')
138     # hanlde drive letter ('c:', ...)
139     if len(chunks) > 1 and len(chunks[0]) == 1 and chunks[0].isalpha():
140         chunks[1] = chunks[0] + ':' + chunks[1]
141         del chunks[0]
142 
143     source = chunks[0]
144     try: source = int(source)
145     except ValueError: pass
146     params = dict( s.split('=') for s in chunks[1:] )
147 
148     cap = None
149     if source == 'synth':
150         Class = classes.get(params.get('class', None), VideoSynthBase)
151         try: cap = Class(**params)
152         except: pass
153     else:
154         cap = cv2.VideoCapture(source)
155         if 'size' in params:
156             w, h = map(int, params['size'].split('x'))
157             cap.set(cv2.cv.CV_CAP_PROP_FRAME_WIDTH, w)
158             cap.set(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT, h)
159     if cap is None or not cap.isOpened():
160         print 'Warning: unable to open video source: ', source
161         if fallback is not None:
162             return create_capture(fallback, None)
163     return cap
164 
165 if __name__ == '__main__':
166     import sys
167     import getopt
168 
169     print __doc__
170 
171     args, sources = getopt.getopt(sys.argv[1:], '', 'shotdir=')
172     args = dict(args)
173     shotdir = args.get('--shotdir', '.')
174     if len(sources) == 0:
175         sources = [ 0 ]
176 
177     caps = map(create_capture, sources)
178     shot_idx = 0
179     while True:
180         imgs = []
181         for i, cap in enumerate(caps):
182             ret, img = cap.read()
183             imgs.append(img)
184             cv2.imshow('capture %d' % i, img)
185         ch = 0xFF & cv2.waitKey(1)
186         if ch == 27:
187             break
188         if ch == ord(' '):
189             for i, img in enumerate(imgs):
190                 fn = '%s/shot_%d_%03d.bmp' % (shotdir, i, shot_idx)
191                 cv2.imwrite(fn, img)
192                 print fn, 'saved'
193             shot_idx += 1
194     cv2.destroyAllWindows()
View Code
第133行：create_capture(source = 0, fallback = presets['chess']) 有两个参数 source 用于指示在哪里获取视频源。fallback ------------
　　声明：s为字符串，rm为要删除的字符序列
　　s.strip(rm) 删除s字符串中开头、结尾处，位于 rm删除序列的字符
　　s.lstrip(rm) 删除s字符串中开头处，位于 rm删除序列的字符
　　s.rstrip(rm) 删除s字符串中结尾处，位于 rm删除序列的字符
　　当rm为空时，默认删除空白符（包括' ', ' ', ' ', ' ')