atlas/web/_js/main/overlap.js

/*
	========================================================================
	The 2022 r/place Atlas

	An atlas of Reddit's 2022 r/place, with information to each
	artwork	of the canvas provided by the community.

	Copyright (c) 2017 Roland Rytz <roland@draemm.li>
	Copyright (c) 2022 Place Atlas contributors

	Licensed under the GNU Affero General Public License Version 3
	https://place-atlas.stefanocoding.me/license.txt
	========================================================================
*/

function initOverlap() {

	window.renderBackground = renderBackground

	// const hovered = []

	buildObjectsList(null, null)
	renderBackground(atlas)
	render()

	document.addEventListener('timeupdate', (event) => {
		sortedAtlas = atlas.concat()
		resetEntriesList(null, null)
		renderBackground(sortedAtlas)
		render()
	})

	applyView()
	render()
	updateLines()

	if (window.location.hash) {
		highlightEntryFromUrl()
	}

	function renderBackground(atlas) {

		backgroundContext.clearRect(0, 0, canvas.width, canvas.height)

		backgroundContext.fillStyle = "rgba(255, 255, 255, 1)"
		backgroundContext.fillRect(0, 0, canvas.width, canvas.height)

		for (let i = 0; i < atlas.length; i++) {

			const path = atlas[i].path

			backgroundContext.beginPath()

			if (path[0]) {
				backgroundContext.moveTo(path[0][0], path[0][1])
			}

			for (let p = 1; p < path.length; p++) {
				backgroundContext.lineTo(path[p][0], path[p][1])
			}

			backgroundContext.closePath()

			backgroundContext.fillStyle = "rgba(0, 0, 255, 0.2)"
			backgroundContext.fill()
		}

		const pixels = backgroundContext.getImageData(0, 0, backgroundCanvas.width, backgroundCanvas.height).data
		let blank = 0

		for (let i = 0; i < pixels.length; i += 4) {
			if (pixels[i] === 255) {
				blank++
			}
		}

		const blankPercentage = (blank / (canvasSize.x * canvasSize.y)) * 100

		console.info(blank + " blank pixels, which are " + blankPercentage.toPrecision(4) + "% of the canvas (" + (100 - blankPercentage).toPrecision(4) + "% mapped)")
	}

}