手机横屏和竖屏状况下的图片旋转

图片渲染要解决的几个主要问题

一、图片默认是水平方向，要设置图片居中

max-height:100%;max-width:100%;position:absolute;left:50%;top:50%;transform:translate(-50%,-50%)"

二、须要旋转的状况是：图片的宽度大于高度，这样旋转后图片显示的就大些

// 获取图片的实际宽度和高度
var picWidth = $("#showPicContent").width(); 
var picHeight = $("#showPicContent").height();
if( picWidth > picHeight) {}

三、在旋转以前要确认好图片的大小，由于旋转后依然是以旋转前的图片的大小

var picRate = picWidth / picHeight;
var windowRate = $(window).height() / $(window).width();
console.log(picRate, windowRate)
if (picRate <= windowRate) {
    PicMaxWidth = $(window).width() * picRate * 0.95
} else {
    PicMaxWidth = $(window).height()
}
$("#showPicContent").css("max-width", PicMaxWidth)

四、旋转的代码 要包含样式中设定的 translate(-50%,-50%)，不然会影响居中的效果

// 旋转的角度 顺时针为正，逆时针为负
$("#showPicContent").css({ "transform": "translate(-50%,-50%) rotate(90deg)" })

五、判断手机横屏与竖屏状态

//判断手机横竖屏状态：
function hengshuping() {
    //alert("hii")
    // window.orientation 只有在手机上才有，网页测试看不出效果
    console.log(window.orientation);
    //$("#showPicContent").css({"transform":"translate(-50%,-50%) rotate(0deg)"})
    if (window.orientation == 180 || window.orientation == 0) {
        //alert("竖屏状态！")
        $("#showPicContent").css("max-width", PicMaxWidth)
        $("#showPicContent").css({ "transform": "translate(-50%,-50%) rotate(90deg)" })
    }
    if (window.orientation == 90 || window.orientation == -90) {
        //alert("横屏状态！")
        $("#showPicContent").css("max-width", "100%")
        $("#showPicContent").css({ "transform": "translate(-50%,-50%) rotate(0deg)" })
    }
}
window.addEventListener("onorientationchange" in window ? "orientationchange" : "resize", hengshuping, false);

完整的代码：实现点击一个图片显示蒙层，蒙层里面有一个图片 与一个关闭按钮

<div style="position:fixed;background:rgba(0,0,0,1.0);top:0;right:0;bottom:0;left:0;z-index:1000;font-size:20px;color:#fff;display:none;" class="backdrop">
        <div style="position:absolute;right:10px;padding-top:5px;color:#f46608;cursor:pointer;z-index:100;" class="closePic">关闭</div>
        <img src="../../dist/img/QQ图片20190604084934.jpg" id="showPicContent" style="max-height:100%;max-width:100%;position:absolute;left:50%;top:50%;transform:translate(-50%,-50%)" />
    </div>

$("#showPic1").click(function() {
            if ($(".backdrop").css("display") == "none") {
                $(".backdrop").css("display", "block");
            }
            var picWidth = $("#showPicContent").width(); // 获取图片显示的宽度和高度
            var picHeight = $("#showPicContent").height();
            //var picWidth = $("#showPicContent").css("width")// 获取图片样式的宽度与高度
            //var picHeight = $("#showPicContent").css("height")

            console.log(picWidth, picHeight)

            if ($(window).width() < 700) {
                if (picWidth > picHeight) {
                    var PicMaxWidth
                    var picRate = picWidth / picHeight;
                    var windowRate = $(window).height() / $(window).width();
                    console.log(picRate, windowRate)
                    if (picRate <= windowRate) {
                        PicMaxWidth = $(window).width() * picRate * 0.95
                    } else {
                        PicMaxWidth = $(window).height()
                    }
                    $("#showPicContent").css("max-width", PicMaxWidth)
                    $("#showPicContent").css({ "transform": "translate(-50%,-50%) rotate(90deg)" })
                    //判断手机横竖屏状态：
                    function hengshuping() {
                        //alert("hii")
                        // window.orientation 只有在手机上才有，网页测试看不出效果
                        console.log(window.orientation);
                        //$("#showPicContent").css({"transform":"translate(-50%,-50%) rotate(0deg)"})
                        if (window.orientation == 180 || window.orientation == 0) {
                            //alert("竖屏状态！")
                            $("#showPicContent").css("max-width", PicMaxWidth)
                            $("#showPicContent").css({ "transform": "translate(-50%,-50%) rotate(90deg)" })
                        }
                        if (window.orientation == 90 || window.orientation == -90) {
                            //alert("横屏状态！")
                            $("#showPicContent").css("max-width", "100%")
                            $("#showPicContent").css({ "transform": "translate(-50%,-50%) rotate(0deg)" })
                        }
                    }
                    window.addEventListener("onorientationchange" in window ? "orientationchange" : "resize", hengshuping, false);
                }
            }
        })


        $("#showPicContent, .closePic").click(function() {
            if ($(".backdrop").css("display") == "block") {
                $(".backdrop").css("display", "none");
            }
        })