function ScaleSize() {

    var clientHeight = document.documentElement.clientHeight; //document.body.clientHeight;
    var clientWidth = document.documentElement.clientWidth;
    var maxImgWidth = 4600;
    var minImgWidth = 1200;
    var maxImgHeight = 3078;

    if (clientWidth >= minImgWidth && clientWidth <= maxImgWidth) {
        document.getElementById("imgTag").style.width = clientWidth + "px";
    } else if (clientWidth > maxImgWidth) {
        document.getElementById("imgTag").style.width = maxImgWidth + "px";
    } else if (clientWidth < minImgWidth) {
        document.getElementById("imgTag").style.width = minImgWidth + "px";
    }
}