如何按比例调整图像大小/保持纵横比？

Question

我有尺寸相当大的图像，我想用 jQuery 缩小它们，同时保持比例受限，即相同的纵横比。

有人可以指出一些代码或解释逻辑吗？

Answer 1

我认为这是一种非常酷的方法 ：

 /**
  * Conserve aspect ratio of the original region. Useful when shrinking/enlarging
  * images to fit into a certain area.
  *
  * @param {Number} srcWidth width of source image
  * @param {Number} srcHeight height of source image
  * @param {Number} maxWidth maximum available width
  * @param {Number} maxHeight maximum available height
  * @return {Object} { width, height }
  */
function calculateAspectRatioFit(srcWidth, srcHeight, maxWidth, maxHeight) {

    var ratio = Math.min(maxWidth / srcWidth, maxHeight / srcHeight);

    return { width: srcWidth*ratio, height: srcHeight*ratio };
 }

Answer 2

看看来自http://ericjuden.com/2009/07/jquery-image-resize/的这段代码

$(document).ready(function() {
    $('.story-small img').each(function() {
        var maxWidth = 100; // Max width for the image
        var maxHeight = 100;    // Max height for the image
        var ratio = 0;  // Used for aspect ratio
        var width = $(this).width();    // Current image width
        var height = $(this).height();  // Current image height

        // Check if the current width is larger than the max
        if(width > maxWidth){
            ratio = maxWidth / width;   // get ratio for scaling image
            $(this).css("width", maxWidth); // Set new width
            $(this).css("height", height * ratio);  // Scale height based on ratio
            height = height * ratio;    // Reset height to match scaled image
            width = width * ratio;    // Reset width to match scaled image
        }

        // Check if current height is larger than max
        if(height > maxHeight){
            ratio = maxHeight / height; // get ratio for scaling image
            $(this).css("height", maxHeight);   // Set new height
            $(this).css("width", width * ratio);    // Scale width based on ratio
            width = width * ratio;    // Reset width to match scaled image
            height = height * ratio;    // Reset height to match scaled image
        }
    });
});

Answer 3

如果我正确理解了这个问题，那么您甚至不需要jQuery。 仅使用CSS即可在客户端上按比例缩小图像：只需将其max-width和max-height为100% 。

<div style="height: 100px">
<img src="http://www.getdigital.de/images/produkte/t4/t4_css_sucks2.jpg"
    style="max-height: 100%; max-width: 100%">
</div>​

这是小提琴： http : //jsfiddle.net/9EQ5c/

Answer 4

为了确定纵横比 ，您需要有一个目标比例。

function getHeight(length, ratio) {
  var height = ((length)/(Math.sqrt((Math.pow(ratio, 2)+1))));
  return Math.round(height);
}

function getWidth(length, ratio) {
  var width = ((length)/(Math.sqrt((1)/(Math.pow(ratio, 2)+1))));
  return Math.round(width);
}

在此示例中，我使用16:10因为这是典型的监视器宽高比。

var ratio = (16/10);
var height = getHeight(300,ratio);
var width = getWidth(height,ratio);

console.log(height);
console.log(width);

上面的结果将是147和300

Answer 5

其实我刚遇到这个问题，我发现的解决方案很奇怪又奇怪

$("#someimage").css({height:<some new height>})

奇迹般地将图像调整为新的高度并保持相同的比例！

Answer 6

这个问题有4个参数

1. 当前图像宽度iX
2. 当前图像高度iY
3. 目标视口宽度cX
4. 目标视口高度cY

并且有3个不同的条件参数

1. cX> cY？
2. iX> cX？
3. iY> cY？

解

1. 找到目标视口F的较小侧
2. 查找当前查看端口L的较大侧
3. 找出两个F / L的因子=因子
4. 将当前端口的两侧乘以系数，即fX = iX *系数； fY = iY *因子

这就是您需要做的。

//Pseudo code


iX;//current width of image in the client
iY;//current height of image in the client
cX;//configured width
cY;//configured height
fX;//final width
fY;//final height

1. check if iX,iY,cX,cY values are >0 and all values are not empty or not junk

2. lE = iX > iY ? iX: iY; //long edge

3. if ( cX < cY )
   then
4.      factor = cX/lE;     
   else
5.      factor = cY/lE;

6. fX = iX * factor ; fY = iY * factor ; 

这是一个成熟的论坛，我没有为您提供代码:)

Answer 7

是否<img src="/path/to/pic.jpg" style="max-width:XXXpx; max-height:YYYpx;" > <img src="/path/to/pic.jpg" style="max-width:XXXpx; max-height:YYYpx;" >帮助？

浏览器会注意保持长宽比不变。

也就是说，当图像宽度大于高度时， max-width宽度会增加，并将按比例计算其高度。 同样，当高度大于宽度时， max-height将生效。

您不需要任何jQuery或javascript。

受ie7 +和其他浏览器（ http://caniuse.com/minmaxwh ）的支持。

Answer 8

这应该适用于所有可能比例的图像

$(document).ready(function() {
    $('.list img').each(function() {
        var maxWidth = 100;
        var maxHeight = 100;
        var width = $(this).width();
        var height = $(this).height();
        var ratioW = maxWidth / width;  // Width ratio
        var ratioH = maxHeight / height;  // Height ratio

        // If height ratio is bigger then we need to scale height
        if(ratioH > ratioW){
            $(this).css("width", maxWidth);
            $(this).css("height", height * ratioW);  // Scale height according to width ratio
        }
        else{ // otherwise we scale width
            $(this).css("height", maxHeight);
            $(this).css("width", height * ratioH);  // according to height ratio
        }
    });
});

Answer 9

$('#productThumb img').each(function() {
    var maxWidth = 140; // Max width for the image
    var maxHeight = 140;    // Max height for the image
    var ratio = 0;  // Used for aspect ratio
    var width = $(this).width();    // Current image width
    var height = $(this).height();  // Current image height
    // Check if the current width is larger than the max
    if(width > height){
        height = ( height / width ) * maxHeight;

    } else if(height > width){
        maxWidth = (width/height)* maxWidth;
    }
    $(this).css("width", maxWidth); // Set new width
    $(this).css("height", maxHeight);  // Scale height based on ratio
});

Answer 10

没有额外的临时变量或括号。

    var width= $(this).width(), height= $(this).height()
      , maxWidth=100, maxHeight= 100;

    if(width > maxWidth){
      height = Math.floor( maxWidth * height / width );
      width = maxWidth
      }
    if(height > maxHeight){
      width = Math.floor( maxHeight * width / height );
      height = maxHeight;
      }

注意：如果width和height属性不适合图像，但他们不知道JS，搜索引擎将不喜欢它。

Answer 11

经过一番反复尝试后，我得出了以下解决方案：

function center(img) {
    var div = img.parentNode;
    var divW = parseInt(div.style.width);
    var divH = parseInt(div.style.height);
    var srcW = img.width;
    var srcH = img.height;
    var ratio = Math.min(divW/srcW, divH/srcH);
    var newW = img.width * ratio;
    var newH = img.height * ratio;
    img.style.width  = newW + "px";
    img.style.height = newH + "px";
    img.style.marginTop = (divH-newH)/2 + "px";
    img.style.marginLeft = (divW-newW)/2 + "px";
}

Answer 12

可以使用CSS来调整尺寸（保持纵横比）。 这是由Dan Dascalescu的帖子启发的进一步简化的答案。

http://jsbin.com/viqare

 img{ max-width:200px; /*Or define max-height*/ } 

 <img src="http://e1.365dm.com/13/07/4-3/20/alastair-cook-ashes-profile_2967773.jpg" alt="Alastair Cook" /> <img src="http://e1.365dm.com/13/07/4-3/20/usman-khawaja-australia-profile_2974601.jpg" alt="Usman Khawaja"/> 

Answer 13

这是对Mehdiway答案的更正。 新的宽度和/或高度未设置为最大值。 以下是一个很好的测试用例（1768 x 1075像素）： http : //spacecoastsports.com/wp-content/uploads/2014/06/sportsballs1.png 。 （由于缺乏声誉，我无法在上面对此发表评论。）

  // Make sure image doesn't exceed 100x100 pixels
  // note: takes jQuery img object not HTML: so width is a function
  // not a property.
  function resize_image (image) {
      var maxWidth = 100;           // Max width for the image
      var maxHeight = 100;          // Max height for the image
      var ratio = 0;                // Used for aspect ratio

      // Get current dimensions
      var width = image.width()
      var height = image.height(); 
      console.log("dimensions: " + width + "x" + height);

      // If the current width is larger than the max, scale height
      // to ratio of max width to current and then set width to max.
      if (width > maxWidth) {
          console.log("Shrinking width (and scaling height)")
          ratio = maxWidth / width;
          height = height * ratio;
          width = maxWidth;
          image.css("width", width);
          image.css("height", height);
          console.log("new dimensions: " + width + "x" + height);
      }

      // If the current height is larger than the max, scale width
      // to ratio of max height to current and then set height to max.
      if (height > maxHeight) {
          console.log("Shrinking height (and scaling width)")
          ratio = maxHeight / height;
          width = width * ratio;
          height = maxHeight;
          image.css("width", width);
          image.css("height", height);
          console.log("new dimensions: " + width + "x" + height);
      }
  }

Answer 14

如果图像是成比例的，则此代码将用图像填充包装器。 如果图像不成比例，则多余的宽度/高度将被裁剪。

    <script type="text/javascript">
        $(function(){
            $('#slider img').each(function(){
                var ReqWidth = 1000; // Max width for the image
                var ReqHeight = 300; // Max height for the image
                var width = $(this).width(); // Current image width
                var height = $(this).height(); // Current image height
                // Check if the current width is larger than the max
                if (width > height && height < ReqHeight) {

                    $(this).css("min-height", ReqHeight); // Set new height
                }
                else 
                    if (width > height && width < ReqWidth) {

                        $(this).css("min-width", ReqWidth); // Set new width
                    }
                    else 
                        if (width > height && width > ReqWidth) {

                            $(this).css("max-width", ReqWidth); // Set new width
                        }
                        else 
                            (height > width && width < ReqWidth)
                {

                    $(this).css("min-width", ReqWidth); // Set new width
                }
            });
        });
    </script>

Answer 15

看看这块...

/**
 * @param {Number} width
 * @param {Number} height
 * @param {Number} destWidth
 * @param {Number} destHeight
 * 
 * @return {width: Number, height:Number}
 */
function resizeKeepingRatio(width, height, destWidth, destHeight)
{
    if (!width || !height || width <= 0 || height <= 0)
    {
        throw "Params error";
    }
    var ratioW = width / destWidth;
    var ratioH = height / destHeight;
    if (ratioW <= 1 && ratioH <= 1)
    {
        var ratio = 1 / ((ratioW > ratioH) ? ratioW : ratioH);
        width *= ratio;
        height *= ratio;
    }
    else if (ratioW > 1 && ratioH <= 1)
    {
        var ratio = 1 / ratioW;
        width *= ratio;
        height *= ratio;
    }
    else if (ratioW <= 1 && ratioH > 1)
    {
        var ratio = 1 / ratioH;
        width *= ratio;
        height *= ratio;
    }
    else if (ratioW >= 1 && ratioH >= 1)
    {
        var ratio = 1 / ((ratioW > ratioH) ? ratioW : ratioH);
        width *= ratio;
        height *= ratio;
    }
    return {
        width : width,
        height : height
    };
}

Answer 16

2个步骤：

步骤1）计算Image的原始宽度/原始高度的比率。

步骤2）将original_width / original_height比值乘以新的所需高度，以获得与新高度相对应的新宽度。

Answer 17

这个问题可以通过 CSS 解决。

.image{
 max-width:*px;
}

Answer 18

调整大小以适合容器，获取比例因子，缩小百分比控制

 $(function () { let ParentHeight = 200; let ParentWidth = 300; $("#Parent").width(ParentWidth).height(ParentHeight); $("#ParentHeight").html(ParentHeight); $("#ParentWidth").html(ParentWidth); var RatioOfParent = ParentHeight / ParentWidth; $("#ParentAspectRatio").html(RatioOfParent); let ChildHeight = 2000; let ChildWidth = 4000; var RatioOfChild = ChildHeight / ChildWidth; $("#ChildAspectRatio").html(RatioOfChild); let ScaleHeight = ParentHeight / ChildHeight; let ScaleWidth = ParentWidth / ChildWidth; let Scale = Math.min(ScaleHeight, ScaleWidth); $("#ScaleFactor").html(Scale); // old scale //ChildHeight = ChildHeight * Scale; //ChildWidth = ChildWidth * Scale; // reduce scale by 10%, you can change the percentage let ScaleDownPercentage = 10; let CalculatedScaleValue = Scale * (ScaleDownPercentage / 100); $("#CalculatedScaleValue").html(CalculatedScaleValue); // new scale let NewScale = (Scale - CalculatedScaleValue); ChildHeight = ChildHeight * NewScale; ChildWidth = ChildWidth * NewScale; $("#Child").width(ChildWidth).height(ChildHeight); $("#ChildHeight").html(ChildHeight); $("#ChildWidth").html(ChildWidth); });

 #Parent { background-color: grey; } #Child { background-color: red; }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <div id="Parent"> <div id="Child"></div> </div> <table> <tr> <td>Parent Aspect Ratio</td> <td id="ParentAspectRatio"></td> </tr> <tr> <td>Child Aspect Ratio</td> <td id="ChildAspectRatio"></td> </tr> <tr> <td>Scale Factor</td> <td id="ScaleFactor"></td> </tr> <tr> <td>Calculated Scale Value</td> <td id="CalculatedScaleValue"></td> </tr> <tr> <td>Parent Height</td> <td id="ParentHeight"></td> </tr> <tr> <td>Parent Width</td> <td id="ParentWidth"></td> </tr> <tr> <td>Child Height</td> <td id="ChildHeight"></td> </tr> <tr> <td>Child Width</td> <td id="ChildWidth"></td> </tr> </table>

Answer 19

将图像调整到特定百分比

// scale can be 0.40, 0.80, etc.
function imageScaler(originalHeight, originalWidth, scale) {
  const scaledWidth = originalWidth * scale;
  const scaledHeight = (originalHeight / originalWidth) * scaledWidth;
  return [scaledHeight, scaledWidth];
}

Answer 20

如果你想要一个特定的纵横比，你可以确定宽度高度，让你有一张 3264×2448 图片纵横比 => 2448 ÷ 3264 =0.75 现在只需检查数字，它在除法上给出 0.75。 比如：对于 16:9 => 9÷16 =0.5625（错了不是 0.75） 现在 4:3 =>3÷4=0.75 （我们明白了） 所以原来的宽高比是 4:3 现在调整图像大小只需做 Width=3264 ÷/× 4 Height=2448 ÷/× 3 ÷ 减少 × 增加希望你能理解并自己编写代码这是非常有效的，因为我们只需要做非常基本的算术只是除法或乘法这么简单。 如果我错了，请告诉我。

Answer 21

这对我来说完全适用于可拖动的项目-AspectRatio：true

.appendTo(divwrapper).resizable({
    aspectRatio: true,
    handles: 'se',
    stop: resizestop 
})