百度地图坐标与像素互相转换的方法

gistfile1.js

pixelToPoint = function(point, zoom, center, bounds) {
    // 像素到坐标
    if (!point) {
        return
    }
    var zoomUnits = getZoomUnits(zoom);
    var mercatorLng = center.lng + zoomUnits * (point.x - bounds.width / 2);
    var mercatorLat = center.lat - zoomUnits * (point.y - bounds.height / 2);
    var mercatorLngLat = {lng: mercatorLng, lat: mercatorLat};
    return mercatorToLngLat(mercatorLngLat)
}

pointToPixel = function(point, zoom, mCenter, bounds) {
    // 坐标到像素
    if (!point) {
        return
    }
    point = lngLatToMercator(point);
    var units = getZoomUnits(zoom);
    var x = Math.round((point.lng - mCenter.lng) / units + bounds.width / 2);
    var y = Math.round((mCenter.lat - point.lat) / units + bounds.height / 2);
    return {x: x, y: y}
}

getZoomUnits = function(zoom) {
    return Math.pow(2, (18 - zoom))
}

mercatorToLngLat = function(mLngLat) {
    var absLngLat, mc;
    absLngLat = {
        lng: Math.abs(mLngLat.lng),
        lat: Math.abs(mLngLat.lat)
    };
    for (var i = 0; i < MCBAND.length; i++) {
        if (absLngLat.lat >= MCBAND[i]) {
            mc = MC2LL[i];
            break
        }
    }
    var lngLat = convertor(mLngLat, mc);
    var lngLat = {
        lng: lngLat.lng.toFixed(6),
        lat: lngLat.lat.toFixed(6)
    };
    return lngLat
}

lngLatToMercator = function(point) {
    var lng_lat, mc;
    point.lng = getLoop(point.lng, -180, 180);
    point.lat = getRange(point.lat, -74, 74);
    lng_lat = {
        lng: point.lng,
        lat: point.lat
    };
    for (var i = 0; i < LLBAND.length; i++) {
        if (lng_lat.lat >= LLBAND[i]) {
            mc = LL2MC[i];
            break
        }
    }
    if (!mc) {
        for (var i = LLBAND.length - 1; i >= 0; i--) {
            if (lng_lat.lat <= -LLBAND[i]) {
                mc = LL2MC[i];
                break
            }
        }
    }
    var cE = convertor(point, mc);
    var lng_lat = {
        lng: cE.lng.toFixed(2),
        lat: cE.lat.toFixed(2)
    };
    return lng_lat
}

getLoop = function(lng, a, b) {
    while (lng > b) {
        lng -= b - a
    }
    while (lng < a) {
        lng += b - a
    }
    return lng
}

getRange = function(lat, a, b) {
    if (a != null) {
        lat = Math.max(lat, a)
    }
    if (b != null) {
        lat = Math.min(lat, b)
    }
    return lat
}

convertor = function(point, mc) {
    if (!point || !mc) {
        return
    }
    var lng = mc[0] + mc[1] * Math.abs(point.lng);
    var c = Math.abs(point.lat) / mc[9];
    var lat = mc[2] + mc[3] * c + mc[4] * c * c + mc[5] * c * c * c + mc[6] * c * c * c * c + mc[7] * c * c * c * c * c + mc[8] * c * c * c * c * c * c;
    lng *= (point.lng < 0 ? -1 : 1);
    lat *= (point.lat < 0 ? -1 : 1);
    return {lng: lng, lat: lat}
}


MCBAND = [12890594.86, 8362377.87, 5591021, 3481989.83, 1678043.12, 0]
LLBAND = [75, 60, 45, 30, 15, 0]
MC2LL = [
    [1.410526172116255e-8, 0.00000898305509648872, -1.9939833816331, 200.9824383106796, -187.2403703815547, 91.6087516669843, -23.38765649603339, 2.57121317296198, -0.03801003308653, 17337981.2],
    [ - 7.435856389565537e-9, 0.000008983055097726239, -0.78625201886289, 96.32687599759846, -1.85204757529826, -59.36935905485877, 47.40033549296737, -16.50741931063887, 2.28786674699375, 10260144.86], 
    [ - 3.030883460898826e-8, 0.00000898305509983578, 0.30071316287616, 59.74293618442277, 7.357984074871, -25.38371002664745, 13.45380521110908, -3.29883767235584, 0.32710905363475, 6856817.37],
    [ - 1.981981304930552e-8, 0.000008983055099779535, 0.03278182852591, 40.31678527705744, 0.65659298677277, -4.44255534477492, 0.85341911805263, 0.12923347998204, -0.04625736007561, 4482777.06],
    [3.09191371068437e-9, 0.000008983055096812155, 0.00006995724062, 23.10934304144901, -0.00023663490511, -0.6321817810242, -0.00663494467273, 0.03430082397953, -0.00466043876332, 2555164.4],
    [2.890871144776878e-9, 0.000008983055095805407, -3.068298e-8, 7.47137025468032, -0.00000353937994, -0.02145144861037, -0.00001234426596, 0.00010322952773, -0.00000323890364, 826088.5]
]
LL2MC = [
    [ - 0.0015702102444, 111320.7020616939, 1704480524535203, -10338987376042340, 26112667856603880, -35149669176653700, 26595700718403920, -10725012454188240, 1800819912950474, 82.5],
    [0.0008277824516172526, 111320.7020463578, 647795574.6671607, -4082003173.641316, 10774905663.51142, -15171875531.51559, 12053065338.62167, -5124939663.577472, 913311935.9512032, 67.5],
    [0.00337398766765, 111320.7020202162, 4481351.045890365, -23393751.19931662, 79682215.47186455, -115964993.2797253, 97236711.15602145, -43661946.33752821, 8477230.501135234, 52.5],
    [0.00220636496208, 111320.7020209128, 51751.86112841131, 3796837.749470245, 992013.7397791013, -1221952.21711287, 1340652.697009075, -620943.6990984312, 144416.9293806241, 37.5],
    [ - 0.0003441963504368392, 111320.7020576856, 278.2353980772752, 2485758.690035394, 6070.750963243378, 54821.18345352118, 9540.606633304236, -2710.55326746645, 1405.483844121726, 22.5],
    [ - 0.0003218135878613132, 111320.7020701615, 0.00369383431289, 823725.6402795718, 0.46104986909093, 2351.343141331292, 1.58060784298199, 8.77738589078284, 0.37238884252424, 7.45]
]

请问从像素到坐标的转换是转换到什么坐标啊？平面坐标还是可视区域坐标啊？