nakarte

Source code of https://map.sikmir.ru (fork)
git clone git://git.sikmir.ru/nakarte
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decoration.magnetic-meridians.js (3222B)

      1 import L from 'leaflet';
      2 import {getDeclination} from '~/lib/magnetic-declination';
      3 import {PrintStaticLayer} from './decorations';
      4 
      5 function radians(degrees) {
      6     return degrees * Math.PI / 180;
      7 }
      8 
      9 function movePoint(p, angle, dist) {
     10     angle = radians(angle);
     11     return L.point(p.x + Math.sin(angle) * dist, p.y - Math.cos(angle) * dist);
     12 }
     13 
     14 class MagneticMeridians extends PrintStaticLayer {
     15     lineThicknessMm = 0.2;
     16     lineIntervalMm = 50;
     17     samplingIntervalMm = 15;
     18     color = '#66c2ff';
     19     overlaySolid = false;
     20 
     21     _makeCanvasToLatLngTransformer(printOptions) {
     22         const projectedBounds = printOptions.pixelBounds;
     23         const scale = projectedBounds.getSize().unscaleBy(printOptions.destPixelSize);
     24         const origin = projectedBounds.min;
     25         return function(pixel) {
     26             return L.CRS.EPSG3857.pointToLatLng(pixel.scaleBy(scale).add(origin), printOptions.zoom);
     27         };
     28     }
     29 
     30     _drawRaster(canvas, printOptions) {
     31         const toLatLng = this._makeCanvasToLatLngTransformer(printOptions);
     32         const ctx = canvas.getContext('2d');
     33         ctx.beginPath();
     34         ctx.strokeStyle = this.color;
     35         ctx.lineWidth = this.lineThicknessMm / 25.4 * printOptions.resolution;
     36         const intervalPx = this.lineIntervalMm / 25.4 * printOptions.resolution;
     37         const samplingPx = this.samplingIntervalMm / 25.4 * printOptions.resolution;
     38         const pageDiagonal = Math.sqrt(
     39             printOptions.destPixelSize.x * printOptions.destPixelSize.x +
     40             printOptions.destPixelSize.y * printOptions.destPixelSize.y
     41         );
     42         const maxSegments = pageDiagonal / 2 / samplingPx;
     43 
     44         function drawLine(p, directionDown) {
     45             ctx.moveTo(p.x, p.y);
     46 
     47             for (let i = 0; i <= maxSegments; i++) {
     48                 let latLng = toLatLng(p);
     49                 let declination = getDeclination(latLng.lat, latLng.lng);
     50                 if (declination === null) {
     51                     break;
     52                 }
     53                 if (directionDown) {
     54                     declination += 180;
     55                 }
     56                 p = movePoint(p, declination, samplingPx);
     57                 ctx.lineTo(p.x, p.y);
     58             }
     59         }
     60 
     61         const center = printOptions.destPixelSize.divideBy(2);
     62         const maxLines = pageDiagonal / 2 / intervalPx;
     63 
     64         drawLine(center);
     65         drawLine(center, true);
     66 
     67         let p = center;
     68         for (let i = 0; i <= maxLines; i++) {
     69             let latLng = toLatLng(p);
     70             let declination = getDeclination(latLng.lat, latLng.lng);
     71             if (declination === null) {
     72                 declination = 0;
     73             }
     74             p = movePoint(p, declination + 90, intervalPx);
     75             drawLine(p);
     76             drawLine(p, true);
     77         }
     78         p = center;
     79         for (let i = 0; i <= maxLines; i++) {
     80             let latLng = toLatLng(p);
     81             let declination = getDeclination(latLng.lat, latLng.lng);
     82             if (declination === null) {
     83                 declination = 0;
     84             }
     85             p = movePoint(p, declination - 90, intervalPx);
     86             drawLine(p);
     87             drawLine(p, true);
     88         }
     89 
     90         ctx.stroke();
     91     }
     92 }
     93 
     94 export {MagneticMeridians};