openlayers加载图片图层png，jpeg等

1.官方实例
tiff测试太大加载不进来，可以转换为其他图片格式

 // Map views always need a projection.  Here we just want to map image
      // coordinates directly to map coordinates, so we create a projection that uses
      // the image extent in pixels.
      var extent = [0, 0, 1024, 968];//图片图层四至
      var projection = new ol.proj.Projection({//定义坐标系
        code: 'xkcd-image',
        units: 'pixels',
        extent: extent
      });

      var map = new ol.Map({
        layers: [
          new ol.layer.Image({
            source: new ol.source.ImageStatic({
              url: 'https://imgs.xkcd.com/comics/online_communities.png',//地址
              projection: projection,
              imageExtent: extent
            })
          })
        ],
        target: 'map',
        view: new ol.View({
          projection: projection,
          center: ol.extent.getCenter(extent),
          zoom: 2,
          maxZoom: 8
        })
      });

[wshop_reward]