我正在尝试使用Flask为我的python OpenCV代码创建一个Web界面,目的是使用画布HTML元素绘制“裁剪区域”以从帧流中提取细节。以下是一些我发现的示例在Stackoverflow上,我能够将OpenCV代码的输出流式传输到img元素,而不是画布或video元素。Python代码:(最小)
import cv2
from flask import Flask, render_template,Response
app = Flask(__name__)
video_capture = cv2.VideoCapture(0)
def gen():
while True:
ret, image = video_capture.read()
cv2.imwrite('t.jpg', image)
yield (b'--frame\r\n'
b'Content-Type: image/jpeg\r\n\r\n' + open('t.jpg', 'rb').read() + b'\r\n')
video_capture.release()
@app.route('/')
def index():
"""Video streaming"""
return render_template('index.html')
@app.route('/video_feed')
def video_feed():
"""Video streaming route. Put this in the src attribute of an img tag."""
return Response(gen(),
mimetype='multipart/x-mixed-replace; boundary=frame')
if __name__ == '__main__':
app.run()
HTML代码:
<html>
<head>
<title>Video Streaming </title>
</head>
<body>
<div>
<h1>Live Video Streaming </h1>
<img id="img" src = "{{ url_for('video_feed') }}">
</div>
</body>
</html>
此具有JavaScript的HTML在Canvas和<img>
中同时显示流。
对于单个静态图像,它需要运行onload()
。对于流MJPEG
,需要使用setInterval()
定期重绘图像。
Chrome
上对我有用,但我的Firefox
仅在Canvas
上显示第一帧。我想我以前有这个问题。可能它需要更多的东西才能正常工作,但我不记得它是什么。
<html>
<head>
<title>Video Streaming </title>
</head>
<body>
<div width="640px" height="480px" style="display:inline-block">
<h1>Image</h1>
<img id="img" src="{{ url_for('video_feed') }}">
</div>
<div width="640px" height="480px" style="display:inline-block">
<h1>Canvas</h1>
<canvas id="canvas" width="640px" height="480px"></canvas>
</div>
<script >
var ctx = document.getElementById("canvas").getContext('2d');
var img = new Image();
img.src = "{{ url_for('video_feed') }}";
// need only for static image
//img.onload = function(){
// ctx.drawImage(img, 0, 0);
//};
// need only for animated image
function refreshCanvas(){
ctx.drawImage(img, 0, 0);
};
window.setInterval("refreshCanvas()", 50);
</script>
</body>
</html>
使用render_template_string
而不是render_template
的完整工作代码,因此每个人都可以将所有代码放入一个文件中并进行测试。
import cv2
from flask import Flask, render_template, render_template_string, Response
app = Flask(__name__)
video_capture = cv2.VideoCapture(0)
def gen():
while True:
ret, image = video_capture.read()
cv2.imwrite('t.jpg', image)
yield (b'--frame\r\n'
b'Content-Type: image/jpeg\r\n\r\n' + open('t.jpg', 'rb').read() + b'\r\n')
video_capture.release()
@app.route('/')
def index():
"""Video streaming"""
#return render_template('index.html')
return render_template_string('''<html>
<head>
<title>Video Streaming </title>
</head>
<body>
<div>
<h1>Image</h1>
<img id="img" src="{{ url_for('video_feed') }}">
</div>
<div>
<h1>Canvas</h1>
<canvas id="canvas" width="640px" height="480px"></canvas>
</div>
<script >
var ctx = document.getElementById("canvas").getContext('2d');
var img = new Image();
img.src = "{{ url_for('video_feed') }}";
// need only for static image
//img.onload = function(){
// ctx.drawImage(img, 0, 0);
//};
// need only for animated image
function refreshCanvas(){
ctx.drawImage(img, 0, 0);
};
window.setInterval("refreshCanvas()", 50);
</script>
</body>
</html>''')
@app.route('/video_feed')
def video_feed():
"""Video streaming route. Put this in the src attribute of an img tag."""
return Response(gen(),
mimetype='multipart/x-mixed-replace; boundary=frame')
if __name__ == '__main__':
app.run()