在鼠标移动时放大图像：到达所有角落

Question

我正在研究缩放功能。此缩放是一个固定框，具有 window 大小的 100%，并且在图像内部具有固定框宽度的 200%。

此缩放需要像这样工作：

当光标位于 window 的中心时，图像应位于中心。
当光标在右上角时，图片应该停留在window的右上角（所以用角到达图片）
当光标在中间下角时，图片应该水平居中并到达总底部，这样我们就可以看到图片的中间下部。
以此类推

我接近了，但无法完美到达角落。这是我的代码片段（请参阅 onmousemove 函数中的注释）：

var Zoom = function(imageZoom) {
  this.urlImage = imageZoom;
  this.img = undefined;
  this.$img = undefined;

  this.init = function() {
    this.loaders("on");
    this.calcs();
  };
  this.calcs = function() {
    var self = this;
    this.img = new Image();
    this.img.onload = function() {
      self.build();
    };
    this.img.src = this.urlImage;
  };
  this.loaders = function(status) {
    switch(status) {
      case "on":
        $('#loader').fadeIn(200);
        break;
      case "off":
        $('#loader').fadeOut(200);
        break;
    }
  };
  this.build = function() {
    var self = this;
    this.$img = $(self.img);
    
    $('#zoom').fadeIn(200).append(this.$img);
    
    this.$img.on('mousedown', function(e) {
      e.preventDefault();
    });
    
    // this is the problematic function
    $('body').on('mousemove', function(e) {
      e.preventDefault();
      // calc the percents of the window where
      var px = 100 * e.pageX / $(window).width(); 
      var py = 100 * e.pageY / $(window).height();

      // calc of the percent pixel of the image
      var fx = self.$img.width() * px / 100;
      var fy = self.$img.height() * py / 100;

      // render it left / 2 and top / 1.5 (the 1.5 value is imaginary!!)
      self.$img.css({'transform': 'translate('+ -(fx/2) +'px, '+ -(fy/1.5)+'px)'});
    });
    self.loaders("off");
  };
};

var zoom = new Zoom("http://dummyimage.com/2000x1230/000/fff");
zoom.init();

#zoom {
 position: fixed;;
 top: 0;
 left: 0;
 width: 100%;
 height: 100%;
 z-index: 1000000;
 display: none;
}
#zoom img {
 width: 200%;
 height: auto;
 position: absolute;
 cursor: crosshair;
 -webkit-touch-callout: none;
 -webkit-user-select: none;
 -khtml-user-select: none;
 -moz-user-select: none;
 -ms-user-select: none;
 user-select: none;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="loader">Loading</div>
<div id="zoom"></div>

问题是我放了 fx/1.5 因为 fx/2 不起作用。但是水平值非常有效。

我可以配置什么值来到达所有角落？为什么左边的值（像素除以 2）在顶部值不工作时工作得很好？

Answer 1

我想你可以通过 CSS 修改来实现你想要的。如果您尝试在 onmousemove 事件中同时使用 clip、transform translate 和 transform scale，则可以按照问题中指定的方式移动图像。请让我知道，如果这是期望的行为，谢谢。

var divPos = {left:0,top:0};
var offset = $("#loader").offset();
$(document).mousemove(function(e){
  divPos = {
    left: e.pageX - offset.left,
    top: e.pageY - offset.top
  };

  console.log("x:" + divPos.left + " y: " + divPos.top);
});

var Zoom = function(imageZoom) {
  this.urlImage = imageZoom;
  this.img = undefined;
  this.$img = undefined;

  this.init = function() {
    this.loaders("on");
    this.calcs();
  };
  
  this.calcs = function() {
    var self = this;
    this.img = new Image();
    this.img.onload = function() {
      self.build();
    };
  
    this.img.src = this.urlImage;
  };
  this.loaders = function(status) {
    switch(status) {
      case "on":
        $('#loader').fadeIn(200);
        break;
      case "off":
        $('#loader').fadeOut(200);
        break;
    }
  };
  this.build = function() {
    var self = this;
    this.$img = $(self.img);
                
    $('#zoom').fadeIn(200).append(this.$img);
                
    this.$img.on('mousedown', function(e) {
      e.preventDefault();
    });

                
    // this is the problematic function
    $('body').on('mousemove', function(e) {
      e.preventDefault();

      var width = $(self.img).width();
      var height = $(self.img).height();
      // img center calculation
      var imgCenterX = width/2;
      var imgCenterY = height/2;
      // translate calculation
      var tx = imgCenterX-divPos.left;
      var ty = imgCenterY-divPos.top;

      // clip calculation
      var c0 = divPos.top/2;
      var c1 = divPos.left/2 + width/2;
      var c2 = divPos.top/2 + height/2;
      var c3 = divPos.left/2;

      console.log(c0 + ',' + c1 + ',' + c2 + ',' + c3);

      var t = 'translate('+ tx +'px, '+ ty +'px)';
      var c = 'rect('+ c0 +'px,'+ c1 +'px,'+ c2 +'px,'+ c3 +'px)';
      self.$img.css({'transform': t + ' scale(2,2)'});
      self.$img.css({'clip': c});
    });
    self.loaders("off");
  };
};

var zoom = new Zoom("http://dummyimage.com/2000x1230/000/fff");
zoom.init();

#zoom {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            z-index: 1000000;
            display: none;
}
#zoom img {
            width: 100%;
            height: 100%;
            position: absolute;
            cursor: crosshair;
            -webkit-touch-callout: none;
            -webkit-user-select: none;
            -khtml-user-select: none;
            -moz-user-select: none;
            -ms-user-select: none;
            user-select: none;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="loader">Loading</div>
<div id="zoom"></div>

Answer 2

你们真的很亲密。获取垂直百分比时，您只需要计算 image.height - window.height。

这也适用于不同的图像纵横比，因为它在计算时会考虑图像高度。宽度不是问题，因为它总是 window 宽度的两倍。

var Zoom = function(imageZoom) {
  this.urlImage = imageZoom;
  this.img = undefined;
  this.$img = undefined;

  this.init = function() {
    this.loaders("on");
    this.calcs();
  };
  this.calcs = function() {
    var self = this;
    this.img = new Image();
    this.img.onload = function() {
      self.build();
    };
    this.img.src = this.urlImage;
  };
  this.loaders = function(status) {
    switch (status) {
      case "on":
        $('#loader').fadeIn(200);
        break;
      case "off":
        $('#loader').fadeOut(200);
        break;
    }
  };
  this.build = function() {
    var self = this;
    this.$img = $(self.img);

    $('#zoom').fadeIn(200).append(this.$img);

    this.$img.on('mousedown', function(e) {
      e.preventDefault();
    });

    // this is the problematic function
    $('body').on('mousemove', function(e) {
      e.preventDefault();

      var wx = $(window).width();
      var wy = $(window).height();
      var iy = self.$img.height();

      var px = e.pageX;
      var py = e.pageY;

      var tx = -1 * (px / wx) * wx;
      var ty = -1 * (py / wy) * (iy - wy);

      self.$img.css({
        'transform': 'translate(' + tx + 'px, ' + ty + 'px)'
      });
    });
    self.loaders("off");
  };
};

var zoom = new Zoom("http://dummyimage.com/2000x1200/000/fff");
zoom.init();

#zoom {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 1000000;
  display: none;
}
#zoom img {
  width: 200%;
  height: 100%;
  height: auto;
  position: absolute;
  cursor: crosshair;
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -khtml-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}
body {
  margin: 0;
}
* {
  box-sizing: border-box;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="loader">Loading</div>
<div id="zoom"></div>

作为奖励：

如果你想摆脱图像宽高比高时留下的空白 space (jsfiddle), you can make sure the image height is at least equal to window height (jsfiddle)。但是，在这种情况下您需要设置 width: auto，因此图像的宽度不会总是 window 的两倍。

在鼠标移动时放大图像：到达所有角落

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