javascript - 如何使整个图像比较滑块居中

Question

当我设法移动图像比较滑块时，实际的“滑块”会落在后面。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" width="650" height="450">
    </div>
    <div class="img-comp-img img-comp-overlay">
      <img src="img/ysl_after.jpg" width="650" height="450">
    </div>
  </div>

标签： javascriptcssimagecenter

Answer 1

我想将使用图像比较滑块比较的两张图像带到页面的中心。W3Schools 上的代码可用于使用滑块比较图像，但没有关于居中的建议。所以我所做的就是放置 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" width="300" height="200">
  </div>
  <div class="img-comp-img img-comp-overlay">
    <img src="img_forest.jpg" width="300" height="200">
  </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>