场景
Node-RED简介与Windows上安装、启动和运行示例：
https://blog.csdn.net/BADAO_LIUMANG_QIZHI/article/details/121884766
Node-RED怎样导出导入流程为json文件：
https://blog.csdn.net/BADAO_LIUMANG_QIZHI/article/details/124130985
Node-RED安装图形化节点dashboard实现订阅mqtt主题并在仪表盘中显示温度：
https://blog.csdn.net/BADAO_LIUMANG_QIZHI/article/details/121992760
在上面的基础上，怎样访问电脑摄像头并截取进行预览。
注：
博客：
https://blog.csdn.net/badao_liumang_qizhi
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实现
1、节点管理-安装node-red-ui-webcam节点
2、设计流程如下
3、流程json数据
[ { "id": "f4a4d8eab7935bc8", "type": "tab", "label": "流程 3", "disabled": false, "info": "", "env": [] }, { "id": "c428312d1f6165d1", "type": "mqtt-broker", "name": "mqtt", "broker": "127.0.0.1", "port": "1883", "clientid": "", "autoConnect": true, "usetls": false, "protocolVersion": "4", "keepalive": "60", "cleansession": true, "birthTopic": "", "birthQos": "0", "birthPayload": "", "birthMsg": {}, "closeTopic": "", "closeQos": "0", "closePayload": "", "closeMsg": {}, "willTopic": "", "willQos": "0", "willPayload": "", "willMsg": {}, "sessionExpiry": "" }, { "id": "51eee50b4ec9422f", "type": "ui_group", "name": "dashboardDemo", "tab": "29ae4c620f43ee0d", "order": 1, "disp": true, "width": "6", "collapse": false, "className": "" }, { "id": "29ae4c620f43ee0d", "type": "ui_tab", "name": "Home", "icon": "dashboard", "disabled": false, "hidden": false }, { "id": "a506c767a5c1edbd", "type": "ui_base", "theme": { "name": "theme-light", "lightTheme": { "default": "#0094CE", "baseColor": "#0094CE", "baseFont": "-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Oxygen-Sans,Ubuntu,Cantarell,Helvetica Neue,sans-serif", "edited": true, "reset": false }, "darkTheme": { "default": "#097479", "baseColor": "#097479", "baseFont": "-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Oxygen-Sans,Ubuntu,Cantarell,Helvetica Neue,sans-serif", "edited": false }, "customTheme": { "name": "Untitled Theme 1", "default": "#4B7930", "baseColor": "#4B7930", "baseFont": "-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Oxygen-Sans,Ubuntu,Cantarell,Helvetica Neue,sans-serif" }, "themeState": { "base-color": { "default": "#0094CE", "value": "#0094CE", "edited": false }, "page-titlebar-backgroundColor": { "value": "#0094CE", "edited": false }, "page-backgroundColor": { "value": "#fafafa", "edited": false }, "page-sidebar-backgroundColor": { "value": "#ffffff", "edited": false }, "group-textColor": { "value": "#1bbfff", "edited": false }, "group-borderColor": { "value": "#ffffff", "edited": false }, "group-backgroundColor": { "value": "#ffffff", "edited": false }, "widget-textColor": { "value": "#111111", "edited": false }, "widget-backgroundColor": { "value": "#0094ce", "edited": false }, "widget-borderColor": { "value": "#ffffff", "edited": false }, "base-font": { "value": "-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Oxygen-Sans,Ubuntu,Cantarell,Helvetica Neue,sans-serif" } }, "angularTheme": { "primary": "indigo", "accents": "blue", "warn": "red", "background": "grey", "palette": "light" } }, "site": { "name": "Node-RED Dashboard", "hideToolbar": "false", "allowSwipe": "false", "lockMenu": "false", "allowTempTheme": "true", "dateFormat": "DD/MM/YYYY", "sizes": { "sx": 48, "sy": 48, "gx": 6, "gy": 6, "cx": 6, "cy": 6, "px": 0, "py": 0 } } }, { "id": "248cbbb0.18e794", "type": "ui_group", "name": "MyGroup", "tab": "3f79c420.cfc1bc", "order": 1, "disp": true, "width": "6", "collapse": false }, { "id": "3f79c420.cfc1bc", "type": "ui_tab", "name": "Home", "icon": "dashboard", "disabled": false, "hidden": false }, { "id": "a0954be5.a7f7e8", "type": "ui_group", "name": "MyInput", "tab": "3f79c420.cfc1bc", "order": 2, "disp": true, "width": "6", "collapse": false }, { "id": "508bd6f8398ab80f", "type": "ui_group", "name": "OpenWeatherMap", "tab": "3f79c420.cfc1bc", "order": 3, "disp": true, "width": "6", "collapse": false }, { "id": "8824dea1.83e31", "type": "websocket-client", "path": "ws://localhost:9898/", "tls": "", "wholemsg": "false" }, { "id": "51c3503.61936b", "type": "MySQLdatabase", "name": "", "host": "127.0.0.1", "port": "3306", "db": "test", "tz": "", "charset": "UTF8" }, { "id": "89952106.631b3", "type": "ui_group", "name": "IFrame", "tab": "5967b7da.b44598", "order": 3, "disp": true, "width": "6", "collapse": false }, { "id": "5967b7da.b44598", "type": "ui_tab", "name": "Home", "icon": "dashboard", "order": 1, "disabled": false, "hidden": false }, { "id": "531fcba07de311b5", "type": "ui_group", "name": "Image", "tab": "5967b7da.b44598", "order": 2, "disp": true, "width": "6", "collapse": false }, { "id": "4d266930e254e1ee", "type": "ui_group", "name": "WebCam", "tab": "5967b7da.b44598", "order": 1, "disp": true, "width": "10", "collapse": false }, { "id": "2855a617781cded9", "type": "ui_group", "name": "WebCam", "tab": "5967b7da.b44598", "order": 1, "disp": true, "width": "10", "collapse": false, "className": "" }, { "id": "96ec2b1fa3684c6b", "type": "ui_webcam", "z": "f4a4d8eab7935bc8", "name": "", "group": "2855a617781cded9", "order": 0, "width": "8", "height": "6", "countdown": false, "autoStart": false, "hideCaptureButton": false, "showImage": "2", "mirror": true, "format": "png", "x": 300, "y": 240, "wires": [ [ "488b1488202928f5" ] ] }, { "id": "488b1488202928f5", "type": "image", "z": "f4a4d8eab7935bc8", "name": "", "width": 160, "data": "payload", "dataType": "msg", "thumbnail": false, "active": true, "pass": false, "outputs": 0, "x": 480, "y": 240, "wires": [] } ]