原生弹窗，图片宽高自适应

弹窗图片宽高自适应

<div class="modal fade hide" id="modal">
    <div class="modal-content">
        <div class="close-btn" id="close-btn"></div>
        <img src="./images/reward.png" alt="reward" />
    </div>
</div>

<script>
    window.onload = function () {
      const rewardIcon = document.getElementById('reward-icon');
      const modal = document.getElementById('modal');
      const closeModal = document.getElementById('close-btn');
      rewardIcon.addEventListener('click', function () {
          modal.classList.remove('hide');
          document.body.classList.add('modal-open');
       });
      closeModal.addEventListener('click', function () {
          modal.classList.add('hide');
          document.body.classList.remove('modal-open');
      })
    }
</script>

// 灰色背景
.modal {
    position: fixed;
    right: 0;
    left: 0;
    bottom: 0;
    top: 0;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
}

// 弹窗主内容，白底，宽度固定，高度根据内容自适应
.modal-content {
    position: relative;
    width: 930px;
    height: auto;
    padding: 60px;
    -webkit-border-radius: 4px;
    -moz-border-radius: 4px;
    border-radius: 4px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.5);
    background: #f9f9f9;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: opacity 1s ease-in;
    opacity: 1;
    visibility: visible;
}

// 关闭按钮，使用雪碧图
.modal .modal-content .close-btn {
    position: absolute;
    top: -18px;
    right: -18px;
    background: url("../images/fancybox_sprite@2x.png") no-repeat;
    background-size: 44px 152px;
    width: 36px;
    height: 36px;
    cursor: pointer;
}

//  图片内容宽高自适应
.modal .modal-content img {
    display: block;
    width: auto;
    height: auto;
    max-width: 100%;
    max-height: 100%;
}

.hide {
    display: none;
    opacity: 0;
    visibility: hidden;
}

// 打开弹窗，固定背景，不随页面滚动
.modal-open {
    overflow-y: hidden;
}

demo地址，最底下荣誉资质