js图片大小限制,设置

//图片大小自动脚本
    function AutoResizeImage(maxWidth, maxHeight, objImg) {
        var img = new Image();
        img.src = objImg.src;
        var hRatio;
        var wRatio;
        var Ratio = 1;
        var w = img.width;
        var h = img.height;
        wRatio = maxWidth / w;
        hRatio = maxHeight / h;
        if (maxWidth == 0 && maxHeight == 0) {
            Ratio = 1;
        } else if (maxWidth == 0) { //
            if (hRatio < 1) Ratio = hRatio;
        } else if (maxHeight == 0) {
            if (wRatio < 1) Ratio = wRatio;
        } else if (wRatio < 1 || hRatio < 1) {
            Ratio = (wRatio <= hRatio ? wRatio : hRatio);
        }
        if (Ratio < 1) {
            w = w * Ratio;
            h = h * Ratio;
        }
        objImg.height = h;
        objImg.width = w;
    }