调整HTML5画布的大小以适合窗口

2020/09/28 15:41 · javascript ·  · 0评论

如何自动缩放HTML5 <canvas>元素以适合页面?

例如,我可以<div>通过将heightwidth属性设置为100%来缩放,但是<canvas>不会缩放吗?

我相信我已经找到了一个优雅的解决方案:

的JavaScript

/* important! for alignment, you should make things
 * relative to the canvas' current width/height.
 */
function draw() {
  var ctx = (a canvas context);
  ctx.canvas.width  = window.innerWidth;
  ctx.canvas.height = window.innerHeight;
  //...drawing code...
}

的CSS

html, body {
  width:  100%;
  height: 100%;
  margin: 0;
}

到目前为止,对我没有太大的负面性能影响。

以下解决方案最适合我。由于我对编码还比较陌生,因此我希望直观地确认某件事正在按我的预期方式工作。我在以下网站上找到它:http :
//htmlcheats.com/html/resize-the-html5-canvas-dyamically/

这是代码:

<!DOCTYPE html>

<head>
    <meta charset="utf-8">
    <title>Resize HTML5 canvas dynamically | www.htmlcheats.com</title>
    <style>
    html, body {
      width: 100%;
      height: 100%;
      margin: 0px;
      border: 0;
      overflow: hidden; /*  Disable scrollbars */
      display: block;  /* No floating content on sides */
    }
    </style>
</head>

<body>
    <canvas id='c' style='position:absolute; left:0px; top:0px;'>
    </canvas>

    <script>
    (function() {
        var
        // Obtain a reference to the canvas element using its id.
        htmlCanvas = document.getElementById('c'),
        // Obtain a graphics context on the canvas element for drawing.
        context = htmlCanvas.getContext('2d');

       // Start listening to resize events and draw canvas.
       initialize();

       function initialize() {
           // Register an event listener to call the resizeCanvas() function 
           // each time the window is resized.
           window.addEventListener('resize', resizeCanvas, false);
           // Draw canvas border for the first time.
           resizeCanvas();
        }

        // Display custom canvas. In this case it's a blue, 5 pixel 
        // border that resizes along with the browser window.
        function redraw() {
           context.strokeStyle = 'blue';
           context.lineWidth = '5';
           context.strokeRect(0, 0, window.innerWidth, window.innerHeight);
        }

        // Runs each time the DOM window resize event fires.
        // Resets the canvas dimensions to match window,
        // then draws the new borders accordingly.
        function resizeCanvas() {
            htmlCanvas.width = window.innerWidth;
            htmlCanvas.height = window.innerHeight;
            redraw();
        }
    })();

    </script>
</body> 
</html>

蓝色边框为您显示了调整大小的画布的边缘,并且始终沿窗口的边缘,在所有4侧均可见,而上述其他一些答案并非如此。希望能帮助到你。

基本上,您要做的就是将onresize事件绑定到您的身体,一旦捕获到该事件,您只需要使用window.innerWidth和window.innerHeight调整画布的大小即可。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Canvas Resize</title>

    <script type="text/javascript">
        function resize_canvas(){
            canvas = document.getElementById("canvas");
            if (canvas.width  < window.innerWidth)
            {
                canvas.width  = window.innerWidth;
            }

            if (canvas.height < window.innerHeight)
            {
                canvas.height = window.innerHeight;
            }
        }
    </script>
</head>

<body onresize="resize_canvas()">
        <canvas id="canvas">Your browser doesn't support canvas</canvas>
</body>
</html>

根据浏览器客户端的尺寸设置画布坐标空间的宽度和高度要求您在调整浏览器大小时重新调整大小并重新绘制。

较不复杂的解决方案是在Javascript变量中保留可绘制的尺寸,但根据screen.width,screen.height尺寸设置画布尺寸。使用CSS来适合:

#containingDiv { 
  overflow: hidden;
}
#myCanvas {
  position: absolute; 
  top: 0px;
  left: 0px;
} 

浏览器窗口通常不会比屏幕本身大(除非错误地报告了屏幕分辨率,因为不匹配的双显示器可能会出现错误),因此背景不会显示,像素比例也不会改变。除非使用CSS缩放画布,否则画布像素将与屏幕分辨率成正比。

纯CSS方法增加@jerseyboy上面的溶液中。

可在Firefox(在v29中测试),Chrome(在v34中测试)和Internet Explorer(在v11中测试)中运行。

<!DOCTYPE html>
<html>
    <head>
    <style>
        html,
        body {
            width: 100%;
            height: 100%;
            margin: 0;
        }
        canvas {
            background-color: #ccc;
            display: block;
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            width: 100%;
            height: 100%;
        }
    </style>
</head>
<body>
    <canvas id="canvas" width="500" height="500"></canvas>
    <script>
        var canvas = document.getElementById('canvas');
        if (canvas.getContext) {
            var ctx = canvas.getContext('2d');
            ctx.fillRect(25,25,100,100);
            ctx.clearRect(45,45,60,60);
            ctx.strokeRect(50,50,50,50);
        }
    </script>
</body>
</html>

链接到示例:http : //temporaer.net/open/so/140502_canvas-fit-to-window.html

但是请保重,正如@jerseyboy在他的评论中所述:

使用CSS重新缩放画布很麻烦。至少在Chrome和Safari上,鼠标/触摸事件的位置与画布像素位置不会1:1对应,因此您必须转换坐标系。

function resize() {

    var canvas = document.getElementById('game');
    var canvasRatio = canvas.height / canvas.width;
    var windowRatio = window.innerHeight / window.innerWidth;
    var width;
    var height;

    if (windowRatio < canvasRatio) {
        height = window.innerHeight;
        width = height / canvasRatio;
    } else {
        width = window.innerWidth;
        height = width * canvasRatio;
    }

    canvas.style.width = width + 'px';
    canvas.style.height = height + 'px';
};

window.addEventListener('resize', resize, false);

除非您希望画布自动放大图像数据(这就是James Black的答案,但是看起来并不漂亮),否则您必须自己调整大小并重新绘制图像。使画布居中

如果您的div完全填满了网页,那么您可以填充该div,因此可以使用画布来填充div。

您可能会发现这很有趣,因为您可能需要使用css来使用百分比,但是,这取决于您使用的浏览器,以及与规范相符的程度:http :
//www.whatwg.org/ specs / web-apps / current-work / multipage / the-canvas-element.html#the-canvas-element

canvas元素的固有尺寸等于坐标空间的大小,其数字以CSS像素表示。但是,可以通过样式表任意设置元素的大小。在渲染期间,将缩放图像以适合此布局大小。

您可能需要获取div的offsetWidth和height,或者获取窗口的高度/宽度并将其设置为像素值。

的CSS

body { margin: 0; } 
canvas { display: block; } 

的JavaScript

window.addEventListener("load", function()
{
    var canvas = document.createElement('canvas'); document.body.appendChild(canvas);
    var context = canvas.getContext('2d');

    function draw()
    {
        context.clearRect(0, 0, canvas.width, canvas.height);
        context.beginPath();
        context.moveTo(0, 0); context.lineTo(canvas.width, canvas.height); 
        context.moveTo(canvas.width, 0); context.lineTo(0, canvas.height); 
        context.stroke();
    }
    function resize()
    {
        canvas.width = window.innerWidth;
        canvas.height = window.innerHeight;
        draw();
    }
    window.addEventListener("resize", resize);
    resize();
});

如果您对保留长宽比感兴趣,并希望在纯CSS中(给出长宽比)进行操作,可以执行以下操作。关键是确定元素大小的元素padding-bottom上的相对于其父级的宽度大小是默认的。此处指定的比例必须与元素上的尺寸比例匹配::contentcontainer100%canvas

// Javascript

var canvas = document.querySelector('canvas'),
    context = canvas.getContext('2d');

context.fillStyle = '#ff0000';
context.fillRect(500, 200, 200, 200);

context.fillStyle = '#000000';
context.font = '30px serif';
context.fillText('This is some text that should not be distorted, just scaled', 10, 40);
/*CSS*/

.container {
  position: relative; 
  background-color: green;
}

.container::after {
  content: ' ';
  display: block;
  padding: 0 0 50%;
}

.wrapper {
  position: absolute;
  top: 0;
  right: 0;
  left: 0;
  bottom: 0;
}

canvas {
  width: 100%;
  height: 100%;
}
<!-- HTML -->

<div class=container>
  <div class=wrapper>
    <canvas width=1200 height=600></canvas>  
  </div>
</div>

使用jQuery,您还可以跟踪窗口的大小并使用jQuery更改画布的宽度。

像这样

$( window ).resize(function() {
 		$("#myCanvas").width($( window ).width())
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<canvas id="myCanvas" width="200" height="100" style="border:1px solid #000000;">
(function() {

    // get viewport size
    getViewportSize = function() {
        return {
            height: window.innerHeight,
            width:  window.innerWidth
        };
    };

    // update canvas size
    updateSizes = function() {
        var viewportSize = getViewportSize();
        $('#myCanvas').width(viewportSize.width).height(viewportSize.height);
        $('#myCanvas').attr('width', viewportSize.width).attr('height', viewportSize.height);
    };

    // run on load
    updateSizes();

    // handle window resizing
    $(window).on('resize', function() {
        updateSizes();
    });

}());

我认为这是我们应该做的:http : //www.html5rocks.com/zh-CN/tutorials/casestudies/gopherwoord-studios-resizing-html5-games/

function resizeGame() {
    var gameArea = document.getElementById('gameArea');
    var widthToHeight = 4 / 3;
    var newWidth = window.innerWidth;
    var newHeight = window.innerHeight;
    var newWidthToHeight = newWidth / newHeight;

    if (newWidthToHeight > widthToHeight) {
        newWidth = newHeight * widthToHeight;
        gameArea.style.height = newHeight + 'px';
        gameArea.style.width = newWidth + 'px';
    } else {
        newHeight = newWidth / widthToHeight;
        gameArea.style.width = newWidth + 'px';
        gameArea.style.height = newHeight + 'px';
    }

    gameArea.style.marginTop = (-newHeight / 2) + 'px';
    gameArea.style.marginLeft = (-newWidth / 2) + 'px';

    var gameCanvas = document.getElementById('gameCanvas');
    gameCanvas.width = newWidth;
    gameCanvas.height = newHeight;
}

window.addEventListener('resize', resizeGame, false);
window.addEventListener('orientationchange', resizeGame, false);

这是一个很小的完整的代码段,其中包含所有答案。按:“运行代码段”,然后按“整页”并调整窗口大小以查看实际运行情况:

function refresh(referenceWidth, referenceHeight, drawFunction) {
  const myCanvas = document.getElementById("myCanvas");
  myCanvas.width = myCanvas.clientWidth;
  myCanvas.height = myCanvas.clientHeight;

  const ratio = Math.min(
    myCanvas.width / referenceWidth,
    myCanvas.height / referenceHeight
  );
  const ctx = myCanvas.getContext("2d");
  ctx.scale(ratio, ratio);

  drawFunction(ctx, ratio);
  window.requestAnimationFrame(() => {
    refresh(referenceWidth, referenceHeight, drawFunction);
  });
}

//100, 100 is the "reference" size. Choose whatever you want.
refresh(100, 100, (ctx, ratio) => {
  //Custom drawing code! Draw whatever you want here.
  const referenceLineWidth = 1;
  ctx.lineWidth = referenceLineWidth / ratio;
  ctx.beginPath();
  ctx.strokeStyle = "blue";
  ctx.arc(50, 50, 49, 0, 2 * Math.PI);
  ctx.stroke();
});
div {
  width: 90vw;
  height: 90vh;
}

canvas {
  width: 100%;
  height: 100%;
  object-fit: contain;
}
<div>
  <canvas id="myCanvas"></canvas>
</div>

此代码段使用canvas.clientWidth和canvas.clientHeight而不是window.innerWidth和window.innerHeight来使代码段在复杂的布局中正确运行。但是,如果将其放在使用全窗口的div中,它也适用于全窗口。这样更灵活。

该片段使用新颖的window.requestAnimationFrame在每一帧重复调整画布的大小。如果您不能使用它,请使用setTimeout。而且,这是低效率的。为了提高效率,请存储clientWidth和clientHeight,并且仅在clientWidth和clientHeight更改时重新计算和重绘。

“参考”分辨率的想法使您可以使用一种分辨率来编写所有绘制命令...,它将自动调整为客户端大小,而无需更改绘制代码。

该代码段是不言自明的,但是如果您愿意,可以用英语进行解释:https : //medium.com/@doomgoober/resizing-canvas-vector-graphics-without-aliasing-7a1f9e684e4d

我正在使用sketch.js,因此在运行画布的init命令后,我使用jquery更改了宽度和高度。尺寸基于父元素。

$('#DrawCanvas')。sketch()。attr('height',$('#DrawCanvas')。parent()。height())。attr('width',$('#DrawCanvas')。parent ()。宽度());

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