Wie man HTML, CSS und jQuery verwendet, um erweiterte Funktionen zum Zuschneiden und Zoomen von Bildern zu implementieren

<div id="image-container">
  <input type="file" id="image-upload" accept="image/*">
  <div class="image-preview"></div>
  <button id="btn-crop">裁剪</button>
  <button id="btn-zoom-in">放大</button>
  <button id="btn-zoom-out">缩小</button>
  <button id="btn-save">保存</button>
</div>

#image-container {
  position: relative;
  width: 400px;
  height: 300px;
  border: 1px solid #ccc;
  overflow: hidden;
}

.image-preview {
  width: 100%;
  height: 100%;
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center;
}

#btn-crop,
#btn-zoom-in,
#btn-zoom-out,
#btn-save {
  display: block;
  margin: 10px 0;
}

#btn-crop,
#btn-save {
  width: 100%;
}

$(document).ready(function() {
  // 图片选择
  $('#image-upload').change(function(e) {
    var file = e.target.files[0];
    var reader = new FileReader();
    reader.onload = function(e) {
      $('.image-preview').css('background-image', 'url(' + e.target.result + ')');
    }
    reader.readAsDataURL(file);
  });

  // 图片裁剪
  var crop = false;
  var startX, startY;

  $('.image-preview').mousedown(function(e) {
    crop = true;
    startX = e.pageX - $(this).offset().left;
    startY = e.pageY - $(this).offset().top;
  });

  $('.image-preview').mousemove(function(e) {
    if (crop) {
      var width = e.pageX - $(this).offset().left - startX;
      var height = e.pageY - $(this).offset().top - startY;
      $(this).css('background-position', -startX + 'px ' + -startY + 'px');
      $(this).css('background-size', (width + 'px') + ' ' + (height + 'px'));
    }
  });

  $(window).mouseup(function() {
    crop = false;
  });

  // 图片缩放
  var zoom = 1;

  $('#btn-zoom-in').click(function() {
    zoom += 0.1;
    $('.image-preview').css('transform', 'scale(' + zoom + ')');
  });

  $('#btn-zoom-out').click(function() {
    zoom -= 0.1;
    $('.image-preview').css('transform', 'scale(' + zoom + ')');
  });

  // 图片保存
  $('#btn-save').click(function() {
    var canvas = document.createElement('canvas');
    var context = canvas.getContext('2d');
    var img = new Image();
    img.src = $('.image-preview').css('background-image').slice(5, -2);
    img.onload = function() {
      canvas.width = img.width;
      canvas.height = img.height;
      context.drawImage(img, 0, 0);
      var dataURL = canvas.toDataURL('image/png');
      window.open(dataURL);
    }
  });
});