如何使整个图像比较滑块居中
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【中文标题】如何使整个图像比较滑块居中【英文标题】：How to center the whole image comparison slider 【发布时间】：2020-05-05 22:24:30 【问题描述】：当我设法移动图像比较滑块时，实际的“滑块”落在后面。滑块JS代码来自https://www.w3schools.com/howto/howto_js_image_comparison.asp
并且可以在那里轻松检查，但我也会将代码粘贴到这里。 我曾尝试使用 Css 网格移动滑块，但如前所述，滑块图标不会随图像一起移动。
function initComparisons()
var x, i;
/* Find all elements with an "overlay" class: */
x = document.getElementsByClassName("img-comp-overlay");
for (i = 0; i < x.length; i++)
/* Once for each "overlay" element:
pass the "overlay" element as a parameter when executing the compareImages function: */
compareImages(x[i]);
function compareImages(img)
var slider, img, clicked = 0, w, h;
/* Get the width and height of the img element */
w = img.offsetWidth;
h = img.offsetHeight;
/* Set the width of the img element to 50%: */
img.style.width = (w / 2) + "px";
/* Create slider: */
slider = document.createElement("DIV");
slider.setAttribute("class", "img-comp-slider");
/* Insert slider */
img.parentElement.insertBefore(slider, img);
/* Position the slider in the middle: */
slider.style.top = (h / 2) - (slider.offsetHeight / 2) + "px";
slider.style.left = (w / 2) - (slider.offsetWidth / 2) + "px";
/* Execute a function when the mouse button is pressed: */
slider.addEventListener("mousedown", slideReady);
/* And another function when the mouse button is released: */
window.addEventListener("mouseup", slideFinish);
/* Or touched (for touch screens: */
slider.addEventListener("touchstart", slideReady);
/* And released (for touch screens: */
window.addEventListener("touchstop", slideFinish);
function slideReady(e)
/* Prevent any other actions that may occur when moving over the image: */
e.preventDefault();
/* The slider is now clicked and ready to move: */
clicked = 1;
/* Execute a function when the slider is moved: */
window.addEventListener("mousemove", slideMove);
window.addEventListener("touchmove", slideMove);
function slideFinish()
/* The slider is no longer clicked: */
clicked = 0;
function slideMove(e)
var pos;
/* If the slider is no longer clicked, exit this function: */
if (clicked == 0) return false;
/* Get the cursor's x position: */
pos = getCursorPos(e)
/* Prevent the slider from being positioned outside the image: */
if (pos < 0) pos = 0;
if (pos > w) pos = w;
/* Execute a function that will resize the overlay image according to the cursor: */
slide(pos);
function getCursorPos(e)
var a, x = 0;
e = e || window.event;
/* Get the x positions of the image: */
a = img.getBoundingClientRect();
/* Calculate the cursor's x coordinate, relative to the image: */
x = e.pageX - a.left;
/* Consider any page scrolling: */
x = x - window.pageXOffset;
return x;
function slide(x)
/* Resize the image: */
img.style.width = x + "px";
/* Position the slider: */
slider.style.left = img.offsetWidth - (slider.offsetWidth / 2) + "px";
initComparisons(); .img-comp-container
margin:auto;
position: relative;
height: 100vh;
width: 100vw
.img-comp-img
position: absolute;
width: auto;
height: auto;
overflow:hidden;
.img-comp-img img
display: block;
vertical-align: middle;
.img-comp-slider
position: absolute;
z-index: 9;
cursor: ew-resize;
width: 0;
height: 0;
border-style: solid;
border-width: 9px 0 9px 14px;
border-color: transparent transparent transparent #ffffff;
<div class="img-comp-container">
<div class="img-comp-img">
<img src="img/ysl_before.jpg" >
</div>
<div class="img-comp-img img-comp-overlay">
<img src="img/ysl_after.jpg" >
</div>
</div>【问题讨论】：
提供的代码似乎在这里工作，也许您为其中一个图像 src 使用了错误的名称？ 提供的代码不会使网站上的滑块居中，希望这能阐明我想要做什么。 【参考方案1】：我相信这可以解决您正在寻找的问题：
将现有容器包装在另一个 div (img-comp-outer-container) 中，从 img-comp-container 中删除边距并将 img-comp-container 的高度/宽度设置为 auto。
然后，您可以设置外部容器的样式以按照您喜欢的方式对齐组件
<div class="img-comp-outer-container"> <!--new div -->
<div class="img-comp-container">
<div class="img-comp-img">
<img src="img_snow.jpg" >
</div>
<div class="img-comp-img img-comp-overlay">
<img src="img_forest.jpg" >
</div>
</div>
</div> <!--new div end -->
.img-comp-outer-container
/* add your styles to move around component */
.img-comp-container
/* margin: auto; */
position: relative;
height: auto; /* was 100vh */
width: auto; /* was 100vw */
【讨论】：
嗨，诺兰，很抱歉这么无知，但我已经按照您的建议编辑了代码并尝试设置 .img-comp-outer-container 边距：0 auto;但它仍然不会使整个滑块居中。你会推荐什么居中？【参考方案2】：我想将我正在使用图像比较滑块进行比较的两张图像带到页面的中心。 W3Schools 上提供的代码可以使用滑块比较图像，但没有关于居中的建议。所以我所做的是我放置了 div id 框并将所有其他类添加到其中，并将框设置为具有高度和宽度的白色，并将 float-right 添加到 img-comp-container。您可以相应地更改框的宽度和高度以使滑块居中。
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
* box-sizing: border-box;
.img-comp-container
float: right; /*new change*/
position: relative;
height: 200px; /*should be the same height as the images*/
.img-comp-img
position: absolute;
width: auto;
height: auto;
overflow:hidden;
.img-comp-img img
display:block;
vertical-align:middle;
.img-comp-slider
position: absolute;
z-index:9;
cursor: ew-resize;
/*set the appearance of the slider:*/
width: 40px;
height: 40px;
background-color: #2196F3;
opacity: 0.7;
border-radius: 50%;
/*new change*/
#box
background: white;
width: 150px;
height: 200px;
</style>
<script>
function initComparisons()
var x, i;
/*find all elements with an "overlay" class:*/
x = document.getElementsByClassName("img-comp-overlay");
for (i = 0; i < x.length; i++)
/*once for each "overlay" element:
pass the "overlay" element as a parameter when executing the compareImages function:*/
compareImages(x[i]);
function compareImages(img)
var slider, img, clicked = 0, w, h;
/*get the width and height of the img element*/
w = img.offsetWidth;
h = img.offsetHeight;
/*set the width of the img element to 50%:*/
img.style.width = (w / 2) + "px";
/*create slider:*/
slider = document.createElement("DIV");
slider.setAttribute("class", "img-comp-slider");
/*insert slider*/
img.parentElement.insertBefore(slider, img);
/*position the slider in the middle:*/
slider.style.top = (h / 2) - (slider.offsetHeight / 2) + "px";
slider.style.left = (w / 2) - (slider.offsetWidth / 2) + "px";
/*execute a function when the mouse button is pressed:*/
slider.addEventListener("mousedown", slideReady);
/*and another function when the mouse button is released:*/
window.addEventListener("mouseup", slideFinish);
/*or touched (for touch screens:*/
slider.addEventListener("touchstart", slideReady);
/*and released (for touch screens:*/
window.addEventListener("touchend", slideFinish);
function slideReady(e)
/*prevent any other actions that may occur when moving over the image:*/
e.preventDefault();
/*the slider is now clicked and ready to move:*/
clicked = 1;
/*execute a function when the slider is moved:*/
window.addEventListener("mousemove", slideMove);
window.addEventListener("touchmove", slideMove);
function slideFinish()
/*the slider is no longer clicked:*/
clicked = 0;
function slideMove(e)
var pos;
/*if the slider is no longer clicked, exit this function:*/
if (clicked == 0) return false;
/*get the cursor's x position:*/
pos = getCursorPos(e)
/*prevent the slider from being positioned outside the image:*/
if (pos < 0) pos = 0;
if (pos > w) pos = w;
/*execute a function that will resize the overlay image according to the cursor:*/
slide(pos);
function getCursorPos(e)
var a, x = 0;
e = e || window.event;
/*get the x positions of the image:*/
a = img.getBoundingClientRect();
/*calculate the cursor's x coordinate, relative to the image:*/
x = e.pageX - a.left;
/*consider any page scrolling:*/
x = x - window.pageXOffset;
return x;
function slide(x)
/*resize the image:*/
img.style.width = x + "px";
/*position the slider:*/
slider.style.left = img.offsetWidth - (slider.offsetWidth / 2) + "px";
</script>
</head>
<body>
<h1>Compare Two Images</h1>
<p>Click and slide the blue slider to compare two images:</p>
<div id="box">/*new change*/
<div class="img-comp-container">
<div class="img-comp-img">
<img src="img_snow.jpg" >
</div>
<div class="img-comp-img img-comp-overlay">
<img src="img_forest.jpg" >
</div>
</div>
</div>
<script>
/*Execute a function that will execute an image compare function for each element with the img-comp-overlay class:*/
initComparisons();
</script>
</body>
</html>
【讨论】：
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