detect stars

[jtleniger]

const sharp = require('sharp')

async function run() {
    let rawData
    let metadata

    try {
        const img = await sharp('input.jpg')

        metadata = await img.metadata()

        rawData = await img
            .greyscale()
            .median()
            .normalise()
            .threshold()
            .raw()
            .toBuffer()
    } catch (error) {
        console.log(error)

        return
    }

    let i = 0
    let whitePixels = []

    for (pixel of rawData.values()) {
        if (!!pixel) {
            whitePixels.push({
                x: i % metadata.width,
                y: Math.floor(i / metadata.width)
            })
        }

        i++
    }
    console.log(`Total pixels: ${rawData.length}`)
    console.log(`White pixels: ${whitePixels.length}`)

    let stars = []

    while (whitePixels.length) {
        let first = whitePixels[0]

        let star = {
            pixels: [first]
        }

        checkNeighbors(whitePixels, star, first)

        stars.push(star)
    }

    console.log(`Stars found: ${stars.length}`)

    stars.forEach((star) => {
        determineCenter(star)
        console.log(`${star.center.x}, ${star.center.y}`)
    })
}

function checkNeighbors(whitePixels, star, first) {
    let neighbors = []

    for (var i = 0; i < whitePixels.length; i++) {
        let pixel = whitePixels[i];

        if (pixel.x <= first.x + 1
            && pixel.x >= first.x - 1
            && pixel.y <= first.y + 1
            && pixel.y >= first.y - 1) {
                neighbors.push(pixel)
        }
    }

    for (var i = 0; i < neighbors.length; i++) {
        whitePixels.splice(whitePixels.indexOf(neighbors[i]), 1)
    }

    star.pixels = star.pixels.concat(neighbors)

    for (var i = 0; i < neighbors.length; i++) {
        checkNeighbors(whitePixels, star, neighbors[i])
    }
}

function determineCenter(star) {
    let sumX = 0
    let sumY = 0

    for (i = 0; i < star.pixels.length; i++) {
        sumX += star.pixels[i].x
        sumY += star.pixels[i].y
    }

    star.center = {
        x: Math.round(sumX / star.pixels.length),
        y: Math.round(sumY / star.pixels.length)
    }
}

run()

[jtleniger]

const sharp = require('sharp')

async function run() {
    let rawData
    let metadata

    try {
        const img = await sharp('input.jpg')

        metadata = await img.metadata()

        rawData = await img
            .greyscale()
            .median()
            .normalise()
            .threshold()
            .raw()
            .toBuffer()
    } catch (error) {
        console.log(error)

        return
    }

    let i = 0
    let whitePixels = []

    console.log(`Width: ${metadata.width} Height: ${metadata.height} Total Pixels: ${metadata.width * metadata.height}`)
    console.log(`Raw Buffer Lengths: ${rawData.length}`)

    for (pixel of rawData.values()) {
        if (!!pixel) {
            whitePixels.push({
                x: i % metadata.width,
                y: Math.floor(i / metadata.width)
            })
        }

        i++
    }
    console.log(`Total pixels: ${rawData.length}`)
    console.log(`White pixels: ${whitePixels.length}`)

    let stars = []

    while (whitePixels.length) {
        let first = whitePixels[0]

        let star = {
            pixels: [first]
        }

        checkNeighbors(whitePixels, star, first)

        stars.push(star)
    }

    console.log(`Stars found: ${stars.length}`)

    stars.forEach((star) => {
        determineCenter(star)
    })

    let blankRaw = await sharp({
        create: {
            width: metadata.width,
            height: metadata.height,
            channels: 3,
            background: 'rgb(0, 0, 0)'
        }
    })
    .greyscale()
    .raw()
    .toBuffer()

    stars.forEach(star => {
        blankRaw[getIndexFromCoordinates(metadata, star.center)] = 255
    })

    await sharp(blankRaw, {
        raw: {
            width: metadata.width,
            height: metadata.height,
            channels: 1
        }
    })
    .toFile('overlay.jpg')
}

function getIndexFromCoordinates(metadata, coords) {
    return (coords.y * metadata.width) + coords.x
}

function checkNeighbors(whitePixels, star, first) {
    let neighbors = []

    for (var i = 0; i < whitePixels.length; i++) {
        let pixel = whitePixels[i];

        if (pixel.x <= first.x + 1
            && pixel.x >= first.x - 1
            && pixel.y <= first.y + 1
            && pixel.y >= first.y - 1) {
                neighbors.push(pixel)
        }
    }

    for (var i = 0; i < neighbors.length; i++) {
        whitePixels.splice(whitePixels.indexOf(neighbors[i]), 1)
    }

    star.pixels = star.pixels.concat(neighbors)

    for (var i = 0; i < neighbors.length; i++) {
        checkNeighbors(whitePixels, star, neighbors[i])
    }
}

function determineCenter(star) {
    let sumX = 0
    let sumY = 0

    for (i = 0; i < star.pixels.length; i++) {
        sumX += star.pixels[i].x
        sumY += star.pixels[i].y
    }

    star.center = {
        x: Math.round(sumX / star.pixels.length),
        y: Math.round(sumY / star.pixels.length)
    }
}

run()