image conversion to latlon

convert.js

var image = new Image(),
    canvas, context, landSquares = [],
    landPixelCount = 0,
    rounding = 10^2;

function errorHandler() {
    console.log(arguments)
}

function writeData() {
    /*
    request
        .post('http://10.0.5.38:7000/data/')
        .set('Accept', 'application/json')
        .send({ data: landSquares })
        .end(function(err) {
            console.log(err);
        });
    */

    var blob = new Blob(
            [ JSON.stringify([[ '1990', landSquares ]]) ],
            { type: 'text/plain' }
        );

    saveAs(blob, 'data.json');
}

function extractSamples(context) {
    // get the image data
    var imageData = context.getImageData(0, 0, canvas.width, canvas.height).data,
        landPixels = 0,
        halfWidth = canvas.width / 2,
        halfHeight = canvas.height / 2,
        maxLat = -90, minLat = 90, maxLon = -180, minLon = 180,
        pos;

    // iterate through the image data
    for (var ii = 0; ii < imageData.length; ii += 4) {
        var rVal = imageData[ii],
            bVal = imageData[ii+1],
            gVal = imageData[ii+2],
            x = ((((ii / 4) % canvas.width) - halfWidth) / halfWidth),
            y = ((Math.floor((ii / 4) / canvas.width) - halfHeight) / halfHeight),
            xRad = x * Math.PI,
            yRad = y * Math.PI;

        // if black we are interested in the value
        if (rVal + bVal + gVal === 0) {
            pos = T5.unproject(xRad, yRad);
            pos.lat = Math.floor(pos.lat); // Math.floor(pos.lat * rounding) / rounding;
            pos.lon = Math.floor(pos.lon); // Math.floor(pos.lon * rounding) / rounding;

            maxLat = Math.max(pos.lat, maxLat);
            minLat = Math.min(pos.lat, minLat);
            maxLon = Math.max(pos.lon, maxLon);
            minLon = Math.min(pos.lon, minLon);

            landSquares.push(x, y, 0.001);
            landPixelCount++;
        }
    }

    console.log('lat: ', minLat, maxLat);
    console.log('lon: ', minLon, maxLon);

    writeData();
    console.log('found ' + landPixelCount + ' pixels');
}

image.src = 'globe/world.jpg';
image.onload = function() {
    canvas = document.createElement('canvas');
    canvas.width = image.width;
    canvas.height = image.height;

    // get the canvas context
    context = canvas.getContext('2d');
    context.drawImage(image, 0, 0);

    // extract the samples
    extractSamples(context);
}