问题描述
如上所示，每个图像的尺寸都不同。轮播高度自动设置为最图像的高度。此行为不是我想要的，因为在这种情况下，当我缩小窗口时，顶部和底部都有空白图像的底部如下图所示（移动屏幕）
期望状态（既可移动，又可移动）
<html lang="en">
<head>
<title>Bootstrap Example</title>
<Meta charset="utf-8">
<Meta name="viewport" content="width=device-width,initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
<style>
/* Make the image fully responsive */
.carousel-inner img {
width: 100%;
height: 100%;
}
div.carousel-item {
background-size:contain;
background-position:center center;
background-repeat:no-repeat no-repeat;
width:100%;
height:100%;
}
</style>
</head>
<body>
<div id="demo" class="carousel slide" data-ride="carousel">
<!-- Indicators -->
<ul class="carousel-indicators">
<li data-target="#demo" data-slide-to="0" class="active"></li>
<li data-target="#demo" data-slide-to="1"></li>
<li data-target="#demo" data-slide-to="2"></li>
</ul>
<!-- The slideshow -->
<div class="carousel-inner">
<div class="carousel-item active" style="background-image:url(https://hips.hearstapps.com/hmg-prod/amv-prod-cad-assets/images/14q3/612022/2015-ford-mustang-gt-instrumented-test-review-car-and-driver-photo-623408-s-original.jpg?fill=2:1&resize=1200:*);" alt="Los Angeles">
</div>
<div class="carousel-item" style="background-image:url(https://static.wixstatic.com/media/61eb8a_19b3e8eaa1d44c16b7954f0d0b1ffb15~mv2.jpg/v1/fill/w_530,h_796,al_c,q_90,usm_0.66_1.00_0.01/61eb8a_19b3e8eaa1d44c16b7954f0d0b1ffb15~mv2.webp);" alt="Chicago">
</div>
<div class="carousel-item" style="background-image:url(https://www.canon.com.tr/media/PCA%20Exercise%20-%20Landscape%20Photography%20exercise-landscape-photos-opener-05_1200%20x%20400_tcm123-1444470.jpg);" alt="New York">
</div>
</div>
<!-- Left and right controls -->
<a class="carousel-control-prev" href="#demo" data-slide="prev">
<span class="carousel-control-prev-icon"></span>
</a>
<a class="carousel-control-next" href="#demo" data-slide="next">
<span class="carousel-control-next-icon"></span>
</a>
</div>
</body>
</html>解决方法
我运行了您的代码，但未显示任何内容，因此我在每个carousel-item中创建了一个新的div，并对其应用了一些CSS样式以满足您的要求。但是对于狭窄的图像，我只使用了img标签。
这是您想要的吗：https://www.codeply.com/p/BLEXWO5Dhq？
.att2 {
background-size: cover;
height: 400px;
width: auto;
background-repeat: no-repeat;
background-position: 50% 50%;
} <head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1.0">
<title>Document</title>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
</head>
<body>
<div class="container">
<div class="row">
<div class="col">
<div id="carouselExampleIndicators1" class="carousel slide" data-ride="carousel">
<ol class="carousel-indicators">
<li data-target="#carouselExampleIndicators1" data-slide-to="0" class="active"></li>
<li data-target="#carouselExampleIndicators1" data-slide-to="1"></li>
<li data-target="#carouselExampleIndicators1" data-slide-to="2"></li>
</ol>
<div class="carousel-inner">
<div class="carousel-item active" >
<div class="att2" style="background-image: url('https://www.canon.com.tr/media/PCA%20Exercise%20-%20Landscape%20Photography%20exercise-landscape-photos-opener-05_1200%20x%20400_tcm123-1444470.jpg')"></div>
</div>
<div class="carousel-item" >
<img src="https://static.wixstatic.com/media/61eb8a_19b3e8eaa1d44c16b7954f0d0b1ffb15~mv2.jpg/v1/fill/w_530,h_796,al_c,q_90,usm_0.66_1.00_0.01/61eb8a_19b3e8eaa1d44c16b7954f0d0b1ffb15~mv2.webp"
class="d-block" alt="..." style="margin: auto; height: 400px;">
<!-- <div class="att2-x" style="background-image: url('https://static.wixstatic.com/media/61eb8a_19b3e8eaa1d44c16b7954f0d0b1ffb15~mv2.jpg/v1/fill/w_530,usm_0.66_1.00_0.01/61eb8a_19b3e8eaa1d44c16b7954f0d0b1ffb15~mv2.webp')"></div> -->
</div>
<div class="carousel-item" >
<div class="att2" style="background-image: url('https://hips.hearstapps.com/hmg-prod/amv-prod-cad-assets/images/14q3/612022/2015-ford-mustang-gt-instrumented-test-review-car-and-driver-photo-623408-s-original.jpg');"></div>
</div>
</div>
<a class="carousel-control-prev" href="#carouselExampleIndicators1" role="button" data-slide="prev">
<span class="carousel-control-prev-icon" aria-hidden="true"></span>
<span class="sr-only">Previous</span>
</a>
<a class="carousel-control-next" href="#carouselExampleIndicators1" role="button" data-slide="next">
<span class="carousel-control-next-icon" aria-hidden="true"></span>
<span class="sr-only">Next</span>
</a>
</div>
</div>
</div>
</div>
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