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6.5 KiB
JavaScript

"use strict";
(self["webpackChunk"] = self["webpackChunk"] || []).push([[6386],{
/***/ 86158:
/***/ (function(__unused_webpack___webpack_module__, __unused_webpack___webpack_exports__, __webpack_require__) {
/* harmony import */ var _src_ol_Map_js__WEBPACK_IMPORTED_MODULE_2__ = __webpack_require__(41376);
/* harmony import */ var _src_ol_source_Raster_js__WEBPACK_IMPORTED_MODULE_1__ = __webpack_require__(47486);
/* harmony import */ var _src_ol_View_js__WEBPACK_IMPORTED_MODULE_5__ = __webpack_require__(54354);
/* harmony import */ var _src_ol_source_XYZ_js__WEBPACK_IMPORTED_MODULE_0__ = __webpack_require__(31998);
/* harmony import */ var _src_ol_layer_js__WEBPACK_IMPORTED_MODULE_3__ = __webpack_require__(42010);
/* harmony import */ var _src_ol_layer_js__WEBPACK_IMPORTED_MODULE_4__ = __webpack_require__(86291);
var minVgi = 0;
var maxVgi = 0.5;
var bins = 10;
/**
* Calculate the Vegetation Greenness Index (VGI) from an input pixel. This
* is a rough estimate assuming that pixel values correspond to reflectance.
* @param {Array<number>} pixel An array of [R, G, B, A] values.
* @return {number} The VGI value for the given pixel.
*/
function vgi(pixel) {
var r = pixel[0] / 255;
var g = pixel[1] / 255;
var b = pixel[2] / 255;
return (2 * g - r - b) / (2 * g + r + b);
}
/**
* Summarize values for a histogram.
* @param {numver} value A VGI value.
* @param {Object} counts An object for keeping track of VGI counts.
*/
function summarize(value, counts) {
var min = counts.min;
var max = counts.max;
var num = counts.values.length;
if (value < min) {// do nothing
} else if (value >= max) {
counts.values[num - 1] += 1;
} else {
var index = Math.floor((value - min) / counts.delta);
counts.values[index] += 1;
}
}
/**
* Use aerial imagery as the input data for the raster source.
*/
var key = 'get_your_own_D6rA4zTHduk6KOKTXzGB';
var attributions = '<a href="https://www.maptiler.com/copyright/" target="_blank">&copy; MapTiler</a> ' + '<a href="https://www.openstreetmap.org/copyright" target="_blank">&copy; OpenStreetMap contributors</a>';
var aerial = new _src_ol_source_XYZ_js__WEBPACK_IMPORTED_MODULE_0__/* ["default"] */ .Z({
attributions: attributions,
url: 'https://api.maptiler.com/tiles/satellite/{z}/{x}/{y}.jpg?key=' + key,
maxZoom: 20,
crossOrigin: ''
});
/**
* Create a raster source where pixels with VGI values above a threshold will
* be colored green.
*/
var raster = new _src_ol_source_Raster_js__WEBPACK_IMPORTED_MODULE_1__/* ["default"] */ .ZP({
sources: [aerial],
/**
* Run calculations on pixel data.
* @param {Array} pixels List of pixels (one per source).
* @param {Object} data User data object.
* @return {Array} The output pixel.
*/
operation: function operation(pixels, data) {
var pixel = pixels[0];
var value = vgi(pixel);
summarize(value, data.counts);
if (value >= data.threshold) {
pixel[0] = 0;
pixel[1] = 255;
pixel[2] = 0;
pixel[3] = 128;
} else {
pixel[3] = 0;
}
return pixel;
},
lib: {
vgi: vgi,
summarize: summarize
}
});
raster.set('threshold', 0.25);
function createCounts(min, max, num) {
var values = new Array(num);
for (var i = 0; i < num; ++i) {
values[i] = 0;
}
return {
min: min,
max: max,
values: values,
delta: (max - min) / num
};
}
raster.on('beforeoperations', function (event) {
event.data.counts = createCounts(minVgi, maxVgi, bins);
event.data.threshold = raster.get('threshold');
});
raster.on('afteroperations', function (event) {
schedulePlot(event.resolution, event.data.counts, event.data.threshold);
});
var map = new _src_ol_Map_js__WEBPACK_IMPORTED_MODULE_2__/* ["default"] */ .Z({
layers: [new _src_ol_layer_js__WEBPACK_IMPORTED_MODULE_3__/* ["default"] */ .Z({
source: aerial
}), new _src_ol_layer_js__WEBPACK_IMPORTED_MODULE_4__/* ["default"] */ .Z({
source: raster
})],
target: 'map',
view: new _src_ol_View_js__WEBPACK_IMPORTED_MODULE_5__/* ["default"] */ .ZP({
center: [-9651695, 4937351],
zoom: 13,
minZoom: 12,
maxZoom: 19
})
});
var timer = null;
function schedulePlot(resolution, counts, threshold) {
if (timer) {
clearTimeout(timer);
timer = null;
}
timer = setTimeout(plot.bind(null, resolution, counts, threshold), 1000 / 60);
}
var barWidth = 15;
var plotHeight = 150;
var chart = d3.select('#plot').append('svg').attr('width', barWidth * bins).attr('height', plotHeight);
var chartRect = chart.node().getBoundingClientRect();
var tip = d3.select(document.body).append('div').attr('class', 'tip');
function plot(resolution, counts, threshold) {
var yScale = d3.scaleLinear().domain([0, d3.max(counts.values)]).range([0, plotHeight]);
var bar = chart.selectAll('rect').data(counts.values);
bar.enter().append('rect');
bar.attr('class', function (count, index) {
var value = counts.min + index * counts.delta;
return 'bar' + (value >= threshold ? ' selected' : '');
}).attr('width', barWidth - 2);
bar.transition().attr('transform', function (value, index) {
return 'translate(' + index * barWidth + ', ' + (plotHeight - yScale(value)) + ')';
}).attr('height', yScale);
bar.on('mousemove', function () {
var index = bar.nodes().indexOf(this);
var threshold = counts.min + index * counts.delta;
if (raster.get('threshold') !== threshold) {
raster.set('threshold', threshold);
raster.changed();
}
});
bar.on('mouseover', function (event) {
var index = bar.nodes().indexOf(this);
var area = 0;
for (var i = counts.values.length - 1; i >= index; --i) {
area += resolution * resolution * counts.values[i];
}
tip.html(message(counts.min + index * counts.delta, area));
tip.style('display', 'block');
tip.transition().style('left', chartRect.left + index * barWidth + barWidth / 2 + 'px').style('top', event.y - 60 + 'px').style('opacity', 1);
});
bar.on('mouseout', function () {
tip.transition().style('opacity', 0).on('end', function () {
tip.style('display', 'none');
});
});
}
function message(value, area) {
var acres = (area / 4046.86).toFixed(0).replace(/\B(?=(\d{3})+(?!\d))/g, ',');
return acres + ' acres at<br>' + value.toFixed(2) + ' VGI or above';
}
/***/ })
},
/******/ function(__webpack_require__) { // webpackRuntimeModules
/******/ var __webpack_exec__ = function(moduleId) { return __webpack_require__(__webpack_require__.s = moduleId); }
/******/ var __webpack_exports__ = (__webpack_exec__(9877), __webpack_exec__(86158));
/******/ }
]);
//# sourceMappingURL=raster.js.map