openlayers 使用canvas绘制圆形头像图标

旧城等待， 2022-11-29 13:09 451阅读 0赞

> 记录一个使用canvas 将一张图片等比缩放，裁剪为一个圆

1、原始图片  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM0ODE3NDQw_size_16_color_FFFFFF_t_70_pic_center]

2、绘制后在地图中呈现的样式  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM0ODE3NDQw_size_16_color_FFFFFF_t_70_pic_center 1]

3、设置样式的函数

/** * 设置Style */
        setStyleOnPersonLocation (feature) { 
          const data = feature.values_
          var imgUrl = 'https://person_head_img/avatar.jpg'
    
          // 绘制圆角矩形
          let canvas = document.createElement('canvas')
          canvas.width = 80
          canvas.height = 80
          var context = canvas.getContext('2d')
          var img = new Image()
          img.src = imgUrl // 原始图片
          let w = canvas.width
          let h = canvas.height
          img.onload = function () { 
            context.save()
            // context.arc(x,y,r,sAngle,eAngle,counterclockwise);
            context.arc(40, 40, 20, 0, 2 * Math.PI) // 从画布上裁剪出这个圆形
            context.clip()
            // context.drawImage(img,x,y,width,height);
            context.drawImage(img, 20, 20, 40, 40)
          }
    
          // 设置style
          return new Style({ 
            image: new Icon({ 
              crossOrigin: 'anonymous',
              img: canvas,
              imgSize: [w, h]
            }),
            text: new Text({ 
              text: data.name,
              offsetY: -26,
              scale: 0.6,
              font: '12px Microsoft YaHei',
              fill: new Fill({ 
                color: '#808080'
              }),
              stroke: new Stroke({ 
                color: '#333',
                width: 1
              })
            })
          })
        },

4、绘制

上面样式设置的函数写好后，这里就可以开始实例化vector , 将其添加到地图中去了

import { Vector as VectorLayer} from 'ol/layer'
    import GeoJSON from 'ol/format/GeoJSON'
    import VectorSource from 'ol/source/Vector'
    import { Point} from 'ol/geom'
    import { boundingExtent, getCenter} from 'ol/extent'
    import { Style, Icon, Stroke, Text, Fill} from 'ol/style'
    
    methods:{ 
    	addlayerToMap(){ 
    		const geologyData = { 
    		  type: 'FeatureCollection',
    		  crs: { 
    		    type: 'Feature'
    		  },
    		  features: [
    			 type: 'Feature',
    		     properties: 'extraData',
    		     id:'userId',
    		     geometry: { 
    		       type: 'Point',
    		       coordinates: [104.050629,30.65769]
    		    }
    		 ]
    		}
    	   let nomalSource = new VectorSource({ 
    	     features: (new GeoJSON()).readFeatures(geologyData)
    	   })
    	   this.shareLocationLayer = new VectorLayer({ 
    	     source: nomalSource,
    	     // style: _this.setStyleOnPersonLocation // 不能在此设置style 否则地图移动会持续触发重绘
    	   })
    	
    	   this.map.addLayer(this.shareLocationLayer)
    	   this.shareLocationLayer.getSource().forEachFeature(featureObj => { 
    	     featureObj.setStyle(_this.setStyleOnPersonLocation(featureObj))
    	   })
    	}
    }

记录记录便于查阅

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM0ODE3NDQw_size_16_color_FFFFFF_t_70_pic_center]: /images/20221124/5b048ec98c3e44ad9cbcde3e00b6a4d2.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM0ODE3NDQw_size_16_color_FFFFFF_t_70_pic_center 1]: /images/20221124/bd015374aed54ed3b40341c236724f0a.png