我们不渲染图层,下面的代码就是我最终使用的。跳过正在操作高程源的栅格图层。
如果对此进行改进,我会在tile缓存中添加一个LRU缓存,也许它可能会挂接到ols缓存中。
var elevation = new ol.source.TileImage({
url: options.template,
projection: elevationGridProjection,
crossOrigin: 'anonymous',
tileGrid: tilegrid
});
let tiles: { [key: string]: HTMLImageElement } = {};
elevation.on("tileloadend", (e) => {
let coord = e.tile.getTileCoord();
tiles[coord.join('-')] = e.tile.getImage();
});
this.map.on('pointermove', (evt) => {
// When user was dragging map, then coordinates didn't change and there's
// no need to continue
if (evt.dragging) {
return;
}
let coordinate = ol.proj.transform(evt.coordinate, this.map.getView().getProjection(), elevationGridProjection);
let tileCoord = tilegrid.getTileCoordForCoordAndResolution(coordinate, this.map.getView().getResolution());
let key = tileCoord.join('-');
if (key in tiles) {
let origin = tilegrid.getOrigin(tileCoord[0]);
let res = tilegrid.getResolution(tileCoord[0]);
let tileSize = tilegrid.getTileSize(tileCoord[0]);
let w = Math.floor(((coordinate[0] - origin[0])/res) % (tileSize[0] | tileSize as number));
let h = Math.floor(((origin[1] - coordinate[1])/res) % (tileSize[1] | tileSize as number));
var canvas = document.createElement("canvas");
canvas.width = tiles[key].width;
canvas.height = tiles[key].height;
// Copy the image contents to the canvas
var ctx = canvas.getContext("2d");
ctx.drawImage(tiles[key], 0, 0);
let img = ctx.getImageData(0, 0, canvas.width, canvas.height);
let imgData = img.data;
let index = (w + h * 256) * 4;
let pixel = [imgData[index + 0], imgData[index + 1], imgData[index + 2], imgData[index + 3]];
let height = (-10000 + ((pixel[0] * 256 * 256 + pixel[1] * 256 + pixel[2]) * 0.01))
console.log(`HEIGHT: ${height}, ${w},${h},${img.width}, ${img.height},${img.data.length} ,${index}, [${pixel.join(',')}]`);
}
});
谢谢:)不知道像素。我们可以将高程图层添加到地图并隐藏它。我更新了我的答案,提供了更详细的解决方案,允许更多的自由,但可以使用它来代替。 –
当您不使用该源渲染图层时,此方法不起作用 - 并且该图层也可能不会隐藏。 – ahocevar
这也是我的理解你的答案 - 我最终使用我发布的答案作为示例。考虑把它打包成可重用的东西。 –