如何获取地图框上像素的颜色 [英] How to get the color of pixels on mapbox

问题描述

我的地图上有雷达栅格，我想通过光标的位置显示雷达的数据颜色.

I have radar raster on my map and i want to show the data color of the radar by the position of the cursor.

雷达示例

我正在尝试通过 map.getCanvas().getContext('2d')获取mapbox画布的上下文，但是它返回null.

I'm trying to get context of a mapbox canvas by map.getCanvas().getContext('2d') but it returns null.

有办法吗?

推荐答案

您可以通过这种方式获取画布上下文(webgl)并检查颜色.

You can obtain the canvas context (webgl) this way and inspect colors.

map.on("mousemove", e => {
  const canvas = map.getCanvas();
  const gl = canvas.getContext('webgl') || canvas.getContext('webgl2');
  if (gl) {
    const { point } = e;
    const { x, y } = point;
    const data = new Uint8Array(4);
    const canvasX = x - canvas.offsetLeft;
    const canvasY = canvas.height - y - canvas.offsetTop;
    gl.readPixels(canvasX, canvasY, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, data);
    const [r, g, b, a] = data;
    const color = `rgba(${r}, ${g}, ${b}, ${a})`;
    console.log(`Color at (${x}, ${y}) = ${color}`);
  }
});

我必须将地图选项 preserveDrawingBuffer 设置为 true 才能获得像素值.

I had to set map option preserveDrawingBuffer to true to be able to get pixel values.

const map = new mapboxgl.Map({
  container: "map",
  style: "mapbox://styles/mapbox/light-v10",
  zoom: 4,
  center: [77.209, 28.6139],
  preserveDrawingBuffer: true
});

此Codepen实现了一个简单的颜色检查器: https://codepen.io/manishraj/full/jONzpzL

This codepen implements a simple color inspector: https://codepen.io/manishraj/full/jONzpzL

这篇关于如何获取地图框上像素的颜色的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！