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| import Map from 'ol/Map.js';
import TileLayer from 'ol/layer/Tile.js';
import View from 'ol/View.js';
import XYZ from 'ol/source/XYZ.js';
import {fromLonLat} from 'ol/proj.js';
const key = 'Get your own API key at https://www.maptiler.com/cloud/';
const attributions =
'<a href="https://www.maptiler.com/copyright/" target="_blank">© MapTiler</a> ' +
'<a href="https://www.openstreetmap.org/copyright" target="_blank">© OpenStreetMap contributors</a>';
const imagery = new TileLayer({
source: new XYZ({
attributions: attributions,
url: 'https://api.maptiler.com/tiles/satellite/{z}/{x}/{y}.jpg?key=' + key,
maxZoom: 20,
crossOrigin: '',
}),
});
const map = new Map({
layers: [imagery],
target: 'map',
view: new View({
center: fromLonLat([-120, 50]),
zoom: 6,
}),
});
const kernels = {
none: [0, 0, 0, 0, 1, 0, 0, 0, 0],
sharpen: [0, -1, 0, -1, 5, -1, 0, -1, 0],
sharpenless: [0, -1, 0, -1, 10, -1, 0, -1, 0],
blur: [1, 1, 1, 1, 1, 1, 1, 1, 1],
shadow: [1, 2, 1, 0, 1, 0, -1, -2, -1],
emboss: [-2, 1, 0, -1, 1, 1, 0, 1, 2],
edge: [0, 1, 0, 1, -4, 1, 0, 1, 0],
};
function normalize(kernel) {
const len = kernel.length;
const normal = new Array(len);
let i,
sum = 0;
for (i = 0; i < len; ++i) {
sum += kernel[i];
}
if (sum <= 0) {
normal.normalized = false;
sum = 1;
} else {
normal.normalized = true;
}
for (i = 0; i < len; ++i) {
normal[i] = kernel[i] / sum;
}
return normal;
}
const select = document.getElementById('kernel');
let selectedKernel = normalize(kernels[select.value]);
select.onchange = function () {
selectedKernel = normalize(kernels[select.value]);
map.render();
};
imagery.on('postrender', function (event) {
convolve(event.context, selectedKernel);
});
function convolve(context, kernel) {
const canvas = context.canvas;
const width = canvas.width;
const height = canvas.height;
const size = Math.sqrt(kernel.length);
const half = Math.floor(size / 2);
const inputData = context.getImageData(0, 0, width, height).data;
const output = context.createImageData(width, height);
const outputData = output.data;
for (let pixelY = 0; pixelY < height; ++pixelY) {
const pixelsAbove = pixelY * width;
for (let pixelX = 0; pixelX < width; ++pixelX) {
let r = 0,
g = 0,
b = 0,
a = 0;
for (let kernelY = 0; kernelY < size; ++kernelY) {
for (let kernelX = 0; kernelX < size; ++kernelX) {
const weight = kernel[kernelY * size + kernelX];
const neighborY = Math.min(
height - 1,
Math.max(0, pixelY + kernelY - half)
);
const neighborX = Math.min(
width - 1,
Math.max(0, pixelX + kernelX - half)
);
const inputIndex = (neighborY * width + neighborX) * 4;
r += inputData[inputIndex] * weight;
g += inputData[inputIndex + 1] * weight;
b += inputData[inputIndex + 2] * weight;
a += inputData[inputIndex + 3] * weight;
}
}
const outputIndex = (pixelsAbove + pixelX) * 4;
outputData[outputIndex] = r;
outputData[outputIndex + 1] = g;
outputData[outputIndex + 2] = b;
outputData[outputIndex + 3] = kernel.normalized ? a : 255;
}
}
context.putImageData(output, 0, 0);
}
|
)
