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<!DOCTYPE html><html lang="zh-CN" data-theme="light"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width,initial-scale=1,viewport-fit=cover"><title>canvas基本使用 | 梦洁小站-属于你我的小天地</title><meta name="author" content="梦洁"><meta name="copyright" content="梦洁"><meta name="format-detection" content="telephone=no"><meta name="theme-color" content="#ffffff"><meta name="description" content="canvas的基本了解 canvas仅仅只是一个画布,定义一个canvas标签,需要通过属性,属性,属性来设置宽度高度(不可以通过样式!),如果不设置默认300*150 不通过属性设置画布的宽度和高度,会造成坐标不准确的问题! canvas必须要通过js来操作 canvas的坐标是从左到右是x轴,从上到下是y轴 vscode书写canvas的时候没有提示,加上/** @type &#12"><meta property="og:type" content="article"><meta property="og:title" content="canvas基本使用"><meta property="og:url" content="https://www.dreamlove.top/4687ae16.html"><meta property="og:site_name" content="梦洁小站-属于你我的小天地"><meta property="og:description" content="canvas的基本了解 canvas仅仅只是一个画布,定义一个canvas标签,需要通过属性,属性,属性来设置宽度高度(不可以通过样式!),如果不设置默认300*150 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fa-chevron-down"></i></a><ul class="menus_item_child"><li><a class="site-page child" target="_blank" rel="noopener" href="https://short.123916.xyz/027a2"><i class="fa-fw fas fa-paperclip"></i><span> clash免费订阅地址</span></a></li><li><a class="site-page child" target="_blank" rel="noopener" href="https://short.123916.xyz/admin/"><i class="fa-fw fas fa-paperclip"></i><span> 短链接生成</span></a></li></ul></div><div class="menus_item"><a class="site-page group" href="javascript:void(0);"><i class="fa-fw fas fa-list"></i><span> 好玩的</span><i class="fas fa-chevron-down"></i></a><ul class="menus_item_child"><li><a class="site-page child" target="_blank" rel="noopener" href="https://make.girls.moe/#/"><i class="fa-fw fas fa-database"></i><span> 动漫头像制作</span></a></li><li><a class="site-page child" target="_blank" rel="noopener" href="http://dfqshy.ysepan.com/"><i class="fa-fw fas fa-database"></i><span> FC游戏大全网盘</span></a></li><li><a class="site-page child" target="_blank" rel="noopener" href="https://www.yikm.net/"><i class="fa-fw fas fa-database"></i><span> 小霸王</span></a></li><li><a class="site-page child" target="_blank" rel="noopener" href="https://www.return8090.com/"><i class="fa-fw fas fa-database"></i><span> 小霸王(广告多)</span></a></li><li><a class="site-page child" target="_blank" rel="noopener" href="http://farm.dreamlove.top"><i class="fa-fw fas fa-database"></i><span> QQ农场经典版</span></a></li><li><a class="site-page child" target="_blank" rel="noopener" href="https://codepip.com/"><i class="fa-fw fas fa-database"></i><span> CssGame</span></a></li><li><a class="site-page child" target="_blank" rel="noopener" href="https://photo.123916.xyz/"><i class="fa-fw fas fa-database"></i><span> 有趣的照片</span></a></li></ul></div><div class="menus_item"><a class="site-page group" href="javascript:void(0);"><i class="fa-fw fas fa-list"></i><span> 其他</span><i class="fas fa-chevron-down"></i></a><ul class="menus_item_child"><li><a class="site-page child" href="/archives/"><i class="fa-fw fas fa-archive"></i><span> 归档</span></a></li><li><a class="site-page child" href="/about/"><i class="fa-fw fas fa-heart"></i><span> 关于</span></a></li><li><a class="site-page child" target="_blank" rel="noopener" href="https://buy.dreamlove.top/"><i class="fa-fw fas fa-heart"></i><span> 购物</span></a></li></ul></div></div><div id="toggle-menu"><a class="site-page" href="javascript:void(0);"><i class="fas fa-bars fa-fw"></i></a></div></div></nav><div id="post-info"><h1 class="post-title">canvas基本使用</h1><div id="post-meta"><div class="meta-firstline"><span class="post-meta-date"><i class="far fa-calendar-alt fa-fw post-meta-icon"></i><span class="post-meta-label">发表于</span><time class="post-meta-date-created" datetime="2022-05-13T15:15:48.000Z" title="发表于 2022-05-13 15:15:48">2022-05-13</time><span class="post-meta-separator">|</span><i class="fas fa-history fa-fw post-meta-icon"></i><span class="post-meta-label">更新于</span><time class="post-meta-date-updated" datetime="2022-05-13T15:15:48.000Z" title="更新于 2022-05-13 15:15:48">2022-05-13</time></span><span class="post-meta-categories"><span class="post-meta-separator">|</span><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/categories/HTML/">HTML</a><i class="fas fa-angle-right post-meta-separator"></i><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/categories/HTML/javscript/">javscript</a></span></div><div class="meta-secondline"><span class="post-meta-separator">|</span><span class="post-meta-wordcount"><i class="far fa-file-word fa-fw post-meta-icon"></i><span class="post-meta-label">字数总计:</span><span class="word-count">1.6k</span><span class="post-meta-separator">|</span><i class="far fa-clock fa-fw post-meta-icon"></i><span class="post-meta-label">阅读时长:</span><span>6分钟</span></span><span class="post-meta-separator">|</span><span class="post-meta-pv-cv" data-flag-title="canvas基本使用"><i class="far fa-eye fa-fw post-meta-icon"></i><span class="post-meta-label">阅读量:</span><span id="busuanzi_value_page_pv"><i class="fa-solid fa-spinner fa-spin"></i></span></span></div></div></div></header><main class="layout" id="content-inner"><div id="post"><article class="post-content" id="article-container"><h3 id="canvas的基本了解"><a href="#canvas的基本了解" class="headerlink" title="canvas的基本了解"></a>canvas的基本了解</h3><ul><li><p>canvas仅仅只是一个画布,定义一个canvas标签,需要通过<strong>属性,属性,属性</strong>来设置宽度高度(不可以通过样式!),如果不设置默认<code>300*150</code></p><ul><li>不通过属性设置画布的宽度和高度,会造成坐标不准确的问题!</li></ul></li><li><p>canvas必须要通过js来操作</p></li><li><p>canvas的坐标是从左到右是x轴,从上到下是y轴</p></li><li><p>vscode书写canvas的时候没有提示,加上<code>/** @type {HTMLCanvasElement} */</code></p><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><script></span><br><span class="line"><span class="comment">/** <span class="doctag">@type</span> {<span class="type">HTMLCanvasElement</span>} */</span></span><br><span class="line"> canvas代码书写</span><br><span class="line"></script></span><br></pre></td></tr></table></figure></li></ul><h3 id="canvas的基本步骤"><a href="#canvas的基本步骤" class="headerlink" title="canvas的基本步骤"></a>canvas的基本步骤</h3><ol><li>获取canvas的节点</li><li>画布创建画笔并选择画笔的绘制类型</li><li>开始绘制</li><li>store()方法绘制 —— stroke() 方法会实际地绘制出通过 moveTo() 和 lineTo() 方法定义的路径。默认颜色是黑色。</li></ol><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><canvas id=<span class="string">"cav"</span> height=<span class="string">"400"</span> width=<span class="string">"400"</span>></canvas></span><br><span class="line"> <span class="language-xml"><span class="tag"><<span class="name">script</span>></span><span class="language-javascript"></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">/** <span class="doctag">@type</span> {<span class="type">HTMLCanvasElement</span>} */</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//1.获取canvas节点(获取画布)</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="keyword">var</span> canvas = <span class="variable language_">document</span>.<span class="title function_">getElementById</span>(<span class="string">"cav"</span>);</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//2.画布创建画笔并选择画笔的绘制类型</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="keyword">var</span> ctx = canvas.<span class="title function_">getContext</span>(<span class="string">"2d"</span>);</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//3.开始绘制</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//绘制的起点</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> ctx.<span class="title function_">moveTo</span>(<span class="number">100</span>,<span class="number">100</span>);</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//有了绘制的起点我们就拖动着笔移动到100,200的坐标点</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> ctx.<span class="title function_">lineTo</span>(<span class="number">100</span>,<span class="number">200</span>);</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//我们再次移动画笔的坐标</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> ctx.<span class="title function_">lineTo</span>(<span class="number">200</span>,<span class="number">300</span>);</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//第一个坐标(100,100)和最后一个坐标(200,300)点闭合</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> ctx.<span class="title function_">closePath</span>();</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//设置填充颜色 - 红色</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//ctx.fillStyle = "red";</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//开始填充颜色</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//ctx.fill();</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//设置绘制线条的颜色</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//ctx.strokeStyle = "yellow";</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//设置绘制线条的粗细</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//ctx.lineWidth = "20";</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//绘制线条</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> ctx.<span class="title function_">stroke</span>();</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> </span><span class="tag"></<span class="name">script</span>></span></span></span><br></pre></td></tr></table></figure><ol start="5"><li><p>绘制效果<img src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205121114879.png" alt="绘制效果" style="zoom:50%"></p></li><li><p>如果想要填充的颜色,画笔可以设置fillStyle指明颜色并且调用fill()方法进行填充</p><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//设置填充颜色 - 红色</span></span><br><span class="line">ctx.<span class="property">fillStyle</span> = <span class="string">"red"</span>;</span><br><span class="line"><span class="comment">//开始填充</span></span><br><span class="line">ctx.<span class="title function_">fill</span>();</span><br></pre></td></tr></table></figure><img src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205121116797.png" alt="绘制效果" style="zoom:50%"></li><li><p>设置线条的颜色</p><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//设置绘制线条的颜色</span></span><br><span class="line">ctx.<span class="property">strokeStyle</span> = <span class="string">"yellow"</span>;</span><br><span class="line"><span class="comment">//设置绘制线条的粗细</span></span><br><span class="line">ctx.<span class="property">lineWidth</span> = <span class="string">"20"</span>;</span><br></pre></td></tr></table></figure><img src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205121120755.png" alt="绘制效果" style="zoom:50%"></li></ol><h3 id="canvas绘制矩形和圆"><a href="#canvas绘制矩形和圆" class="headerlink" title="canvas绘制矩形和圆"></a>canvas绘制矩形和圆</h3><h4 id="绘制矩形"><a href="#绘制矩形" class="headerlink" title="绘制矩形"></a>绘制矩形</h4><ul><li>画笔使用<code>storeRect()</code>方法</li><li>画笔使用<code>fillRect()</code>方法</li></ul><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> cav = <span class="variable language_">document</span>.<span class="title function_">getElementById</span>(<span class="string">"cav"</span>);</span><br><span class="line"><span class="keyword">var</span> ctx = cav.<span class="title function_">getContext</span>(<span class="string">"2d"</span>);</span><br><span class="line">ctx.<span class="title function_">beginPath</span>();</span><br><span class="line"><span class="comment">//绘制线框矩形四个参数分别为 x,y,width,height</span></span><br><span class="line">ctx.<span class="title function_">strokeRect</span>(<span class="number">100</span>,<span class="number">100</span>,<span class="number">150</span>,<span class="number">200</span>);</span><br><span class="line"> <span class="comment">//绘制填充矩形</span></span><br><span class="line"> <span class="comment">//设置填充颜色</span></span><br><span class="line">ctx.<span class="property">fillStyle</span> = <span class="string">'red'</span>;</span><br><span class="line">ctx.<span class="title function_">fillRect</span>(<span class="number">300</span>,<span class="number">100</span>,<span class="number">150</span>,<span class="number">200</span>);</span><br></pre></td></tr></table></figure><h4 id="绘制圆"><a href="#绘制圆" class="headerlink" title="绘制圆"></a>绘制圆</h4><ul><li><p>画笔使用<code>arc()</code>方法</p><ul><li><p>ctx.arc(x, y, radius, startAngle, endAngle, anticlockwise);</p></li><li><p><code>X,Y,radius</code>分别是横坐标,纵坐标,半径</p></li><li><p><code>startAngle:</code> 圆弧的起点,x轴方向开始计算,单位以弧度表示</p><ul><li>(<strong>1弧度等于57度左右</strong>) 因为2<em>PI</em>弧度=360所以1弧度=57度</li><li>所以绘制一个圆直接起始弧度为<code>0</code>,终点弧度为<code>2*Math.PI</code>即可</li></ul></li><li><p><code>endAngle:</code>圆弧的终点,单位以弧度表示</p></li><li><p><code>anticlockwise:</code>可选的<code>Boolean</code>值 ，如果为 <code>true</code>，逆时针绘制圆弧，反之，顺时针绘制。</p><ul><li><p>注意,是绘制,绘制,绘制!,比如其他参数相同,唯独最后一个参数不同,那么图形是完全不同的</p></li><li><p>如图 ctx.arc(50,50,25,0,1,false);顺时针和逆时针绘制效果</p><img src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205121505891.png" alt="绘制效果"></li></ul></li></ul></li></ul><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> cav2 = <span class="variable language_">document</span>.<span class="title function_">getElementById</span>(<span class="string">'cav2'</span>);</span><br><span class="line"><span class="keyword">var</span> ctx = cav2.<span class="title function_">getContext</span>(<span class="string">"2d"</span>);</span><br><span class="line">ctx.<span class="title function_">beginPath</span>();</span><br><span class="line"><span class="comment">//绘制圆 ctx.arc(x, y, radius, startAngle, endAngle, anticlockwise);</span></span><br><span class="line">ctx.<span class="title function_">arc</span>(<span class="number">50</span>,<span class="number">50</span>,<span class="number">25</span>,<span class="number">0</span>,<span class="number">2</span>*<span class="title class_">Math</span>.<span class="property">PI</span>,<span class="literal">false</span>);</span><br><span class="line">ctx.<span class="title function_">stroke</span>();</span><br></pre></td></tr></table></figure><h4 id="绘制字体"><a href="#绘制字体" class="headerlink" title="绘制字体"></a>绘制字体</h4><ul><li>画笔设置<code>font</code>属性可以设置字体的格式<ul><li><a target="_blank" rel="noopener" href="https://developer.mozilla.org/zh-CN/docs/Web/API/CanvasRenderingContext2D/font">API</a></li></ul></li><li>画笔调用<code>fillText</code>可以绘制字体<ul><li>ctx.fillText(text, x, y, [maxWidth]);</li><li><code>text</code>: 绘制的文本</li><li><code>x,y</code>: 坐标</li><li><code>maxWidth</code>: 绘制的最大宽度。如果指定了值，并且经过计算字符串的值比最大宽度还要宽，字体为了适应会水平缩放（如果通过水平缩放当前字体，可以进行有效的或者合理可读的处理）或者使用小号的字体。</li></ul></li></ul><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><canvas id=<span class="string">"cav"</span> height=<span class="string">"400"</span> width=<span class="string">"400"</span>></canvas></span><br><span class="line"><span class="language-xml"><span class="tag"><<span class="name">script</span>></span><span class="language-javascript"></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">/** <span class="doctag">@type</span> {<span class="type">HTMLCanvasElement</span>} */</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//1.获取canvas节点(获取画布)</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="keyword">var</span> canvas = <span class="variable language_">document</span>.<span class="title function_">getElementById</span>(<span class="string">"cav"</span>);</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//2.画布创建画笔并选择画笔的绘制类型</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="keyword">var</span> ctx = canvas.<span class="title function_">getContext</span>(<span class="string">"2d"</span>);</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//绘制文字</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> <span class="comment">//设置绘制文字字体</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> ctx.<span class="property">font</span> = <span class="string">"20px 黑体"</span></span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"> ctx.<span class="title function_">fillText</span>(<span class="string">"叫我将军大人"</span>,<span class="number">10</span>,<span class="number">20</span>);</span></span></span><br><span class="line"><span class="language-javascript"><span class="language-xml"></span><span class="tag"></<span class="name">script</span>></span></span></span><br></pre></td></tr></table></figure><img src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205121546644.png" alt="绘制效果"><h3 id="清空画步和清除指定区域"><a href="#清空画步和清除指定区域" class="headerlink" title="清空画步和清除指定区域"></a>清空画步和清除指定区域</h3><ul><li>均使用画笔当中的clearRect方法,只是传入的值有所区别</li><li>ctx.clearRect(x, y, width, height);<ul><li><code>X,Y</code>: 开始清空的坐标</li><li><code>width</code>: 清空的宽度</li><li><code>height</code>: 清空的高度</li></ul></li></ul><h4 id="清空画布"><a href="#清空画布" class="headerlink" title="清空画布"></a>清空画布</h4><ul><li>ctx.clearRect(0,0,画布的宽度,画布的高度);</li></ul><h4 id="清除指定区域"><a href="#清除指定区域" class="headerlink" title="清除指定区域"></a>清除指定区域</h4><ul><li><p>ctx.clearRect(0,0,40,50)</p></li><li><p>效果</p><img src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205121552458.png" alt="绘制效果"></li></ul><h3 id="canvas绘制一个柱形图"><a href="#canvas绘制一个柱形图" class="headerlink" title="canvas绘制一个柱形图"></a>canvas绘制一个柱形图</h3><h4 id="效果"><a href="#效果" class="headerlink" title="效果"></a>效果</h4><p><img src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205121702131.png" alt="柱形图效果"></p><h4 id="代码"><a href="#代码" class="headerlink" title="代码"></a>代码</h4><figure class="highlight html"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta"><!DOCTYPE <span class="keyword">html</span>></span></span><br><span class="line"><span class="tag"><<span class="name">html</span> <span class="attr">lang</span>=<span class="string">"en"</span>></span></span><br><span class="line"></span><br><span class="line"><span class="tag"><<span class="name">head</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">meta</span> <span class="attr">charset</span>=<span class="string">"UTF-8"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">meta</span> <span class="attr">http-equiv</span>=<span class="string">"X-UA-Compatible"</span> <span class="attr">content</span>=<span class="string">"IE=edge"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">meta</span> <span class="attr">name</span>=<span class="string">"viewport"</span> <span class="attr">content</span>=<span class="string">"width=device-width, initial-scale=1.0"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">title</span>></span>Document<span class="tag"></<span class="name">title</span>></span></span><br><span class="line"><span class="tag"></<span class="name">head</span>></span></span><br><span class="line"></span><br><span class="line"><span class="tag"><<span class="name">body</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">canvas</span> <span class="attr">id</span>=<span class="string">"cav"</span> <span class="attr">height</span>=<span class="string">"600"</span> <span class="attr">width</span>=<span class="string">"800"</span>></span><span class="tag"></<span class="name">canvas</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">style</span>></span><span class="language-css"></span></span><br><span class="line"><span class="language-css"> <span class="selector-id">#cav</span>{</span></span><br><span class="line"><span class="language-css"> <span class="attribute">border</span>: <span class="number">1px</span> solid red;</span></span><br><span class="line"><span class="language-css"> }</span></span><br><span class="line"><span class="language-css"> </span><span class="tag"></<span class="name">style</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">script</span>></span><span class="language-javascript"></span></span><br><span class="line"><span class="language-javascript"> <span class="comment">/** <span class="doctag">@type</span> {<span class="type">HTMLCanvasElement</span>} */</span></span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//1.获取canvas节点(获取画布)</span></span></span><br><span class="line"><span class="language-javascript"> <span class="keyword">var</span> canvas = <span class="variable language_">document</span>.<span class="title function_">getElementById</span>(<span class="string">"cav"</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//2.画布创建画笔并选择画笔的绘制类型</span></span></span><br><span class="line"><span class="language-javascript"> <span class="keyword">var</span> ctx = canvas.<span class="title function_">getContext</span>(<span class="string">"2d"</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//设置线条粗细</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="property">lineWidth</span> = <span class="string">"2"</span>;</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//设置字体</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="property">font</span> = <span class="string">"20px 黑体"</span></span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//绘制坐标轴先</span></span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//y坐标</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"数据可视化"</span>,<span class="number">0</span>,<span class="number">40</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">40</span>,<span class="number">40</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">40</span>,<span class="number">480</span>)</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//150字体</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">40</span>,<span class="number">80</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">20</span>,<span class="number">80</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"150"</span>,<span class="number">10</span>,<span class="number">80</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//120字体</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">40</span>,<span class="number">160</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">20</span>,<span class="number">160</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"120"</span>,<span class="number">10</span>,<span class="number">160</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//90字体</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">40</span>,<span class="number">240</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">20</span>,<span class="number">240</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"90"</span>,<span class="number">20</span>,<span class="number">240</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//60字体</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">40</span>,<span class="number">320</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">20</span>,<span class="number">320</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"60"</span>,<span class="number">20</span>,<span class="number">320</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//30字体</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">40</span>,<span class="number">400</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">20</span>,<span class="number">400</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"30"</span>,<span class="number">20</span>,<span class="number">400</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//0字体</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">40</span>,<span class="number">480</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">20</span>,<span class="number">480</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"0"</span>,<span class="number">20</span>,<span class="number">480</span>);</span></span><br><span class="line"><span class="language-javascript"></span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//x坐标</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">40</span>,<span class="number">480</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">680</span>,<span class="number">480</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//竖线1</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">200</span>,<span class="number">480</span>)</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">200</span>,<span class="number">500</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"食品"</span>,<span class="number">100</span>,<span class="number">500</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//竖线2</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">360</span>,<span class="number">480</span>)</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">360</span>,<span class="number">500</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"数码"</span>,<span class="number">260</span>,<span class="number">500</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//竖线3</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">moveTo</span>(<span class="number">520</span>,<span class="number">480</span>)</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">lineTo</span>(<span class="number">520</span>,<span class="number">500</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"服饰"</span>,<span class="number">420</span>,<span class="number">500</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillText</span>(<span class="string">"箱包"</span>,<span class="number">580</span>,<span class="number">500</span>);</span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">stroke</span>();</span></span><br><span class="line"><span class="language-javascript"> </span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//绘制矩形</span></span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//设置填充矩形颜色</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="property">fillStyle</span> = <span class="string">'hotpink'</span>;</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//食品矩形</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillRect</span>(<span class="number">80</span>,<span class="number">320</span>,<span class="number">80</span>,<span class="number">160</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//数码矩形</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillRect</span>(<span class="number">240</span>,<span class="number">280</span>,<span class="number">80</span>,<span class="number">200</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//服饰矩形</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillRect</span>(<span class="number">400</span>,<span class="number">240</span>,<span class="number">80</span>,<span class="number">240</span>);</span></span><br><span class="line"><span class="language-javascript"> <span class="comment">//箱包矩形</span></span></span><br><span class="line"><span class="language-javascript"> ctx.<span class="title function_">fillRect</span>(<span class="number">560</span>,<span class="number">0</span>,<span class="number">80</span>,<span class="number">480</span>);</span></span><br><span class="line"><span class="language-javascript"></span></span><br><span class="line"><span class="language-javascript"> </span><span class="tag"></<span class="name">script</span>></span> </span><br><span class="line"><span class="tag"></<span class="name">body</span>></span></span><br><span class="line"></span><br><span class="line"><span class="tag"></<span class="name">html</span>></span></span><br></pre></td></tr></table></figure><h4 id="过程图"><a href="#过程图" class="headerlink" title="过程图"></a>过程图</h4><p><img src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205121704140.png" alt="过程图"></p></article><div class="post-copyright"><div class="post-copyright__author"><span class="post-copyright-meta"><i class="fas fa-circle-user fa-fw"></i>文章作者: </span><span class="post-copyright-info"><a href="https://www.dreamlove.top">梦洁</a></span></div><div class="post-copyright__type"><span class="post-copyright-meta"><i class="fas fa-square-arrow-up-right fa-fw"></i>文章链接: </span><span class="post-copyright-info"><a href="https://www.dreamlove.top/4687ae16.html">https://www.dreamlove.top/4687ae16.html</a></span></div><div class="post-copyright__notice"><span class="post-copyright-meta"><i class="fas fa-circle-exclamation fa-fw"></i>版权声明: </span><span class="post-copyright-info">本博客所有文章除特别声明外，均采用 <a href="https://creativecommons.org/licenses/by-nc-sa/4.0/" target="_blank">CC BY-NC-SA 4.0</a> 许可协议。转载请注明来自 <a href="https://www.dreamlove.top" target="_blank">梦洁小站-属于你我的小天地</a>！</span></div></div><div class="tag_share"><div class="post-meta__tag-list"><a class="post-meta__tags" href="/tags/HTML/">HTML</a><a class="post-meta__tags" href="/tags/javscript/">javscript</a><a class="post-meta__tags" href="/tags/canvas/">canvas</a></div><div class="post_share"><div class="social-share" data-image="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205132349743.jpg" data-sites="facebook,twitter,wechat,weibo,qq"></div><link rel="stylesheet" href="https://lib.baomitu.com/butterfly-extsrc/1.1.3/sharejs/dist/css/share.min.css" media="print" onload='this.media="all"'><script src="https://lib.baomitu.com/butterfly-extsrc/1.1.3/sharejs/dist/js/social-share.min.js" defer></script></div></div><nav class="pagination-post" id="pagination"><div class="prev-post pull-left"><a href="/c7600fcc.html" title="LeanCloud白嫖valine评论和避免休眠指南"><img class="cover" src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202205152229804.jpg" 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class="custom-hr"><div id="post-comment"><div class="comment-head"><div class="comment-headline"><i class="fas fa-comments fa-fw"></i><span> 评论</span></div></div><div class="comment-wrap"><div><div id="artalk-wrap"></div></div></div></div></div><div class="aside-content" id="aside-content"><div class="card-widget card-info"><div class="is-center"><div class="avatar-img"><img src="https://oss.dreamlove.top/i/2024/02/02/nw24wu.png" onerror='this.onerror=null,this.src="/img/404.png"' alt="avatar"></div><div class="author-info__name">梦洁</div><div class="author-info__description">小小的字,有大大的梦想~分享我的前端学习过程,经历,错误,和一些其他折腾过程</div></div><div class="card-info-data site-data is-center"><a href="/archives/"><div class="headline">文章</div><div class="length-num">170</div></a><a href="/tags/"><div class="headline">标签</div><div class="length-num">94</div></a><a href="/categories/"><div class="headline">分类</div><div class="length-num">70</div></a></div><a id="card-info-btn" target="_blank" rel="noopener" href="https://github.com/superBiuBiuMan"><i class="fab fa-github"></i><span>关注下我(*￣▽￣*)</span></a><div class="card-info-social-icons is-center"><a class="social-icon" href="mailto:[email protected]" target="_blank" title="Email"><i class="fas fa-envelope" style="color:#4a7dbe"></i></a></div></div><div class="card-widget card-announcement"><div class="item-headline"><i class="fas fa-bullhorn fa-shake"></i><span>公告</span></div><div class="announcement_content">不断更新中,有问题请留言回复(会通过邮箱提醒~)</div></div><div class="sticky_layout"><div class="card-widget" id="card-toc"><div class="item-headline"><i class="fas fa-stream"></i><span>目录</span><span class="toc-percentage"></span></div><div class="toc-content"><ol class="toc"><li class="toc-item toc-level-3"><a class="toc-link" href="#canvas%E7%9A%84%E5%9F%BA%E6%9C%AC%E4%BA%86%E8%A7%A3"><span class="toc-number">1.</span> <span class="toc-text">canvas的基本了解</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#canvas%E7%9A%84%E5%9F%BA%E6%9C%AC%E6%AD%A5%E9%AA%A4"><span class="toc-number">2.</span> <span class="toc-text">canvas的基本步骤</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#canvas%E7%BB%98%E5%88%B6%E7%9F%A9%E5%BD%A2%E5%92%8C%E5%9C%86"><span class="toc-number">3.</span> <span class="toc-text">canvas绘制矩形和圆</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%BB%98%E5%88%B6%E7%9F%A9%E5%BD%A2"><span class="toc-number">3.1.</span> <span class="toc-text">绘制矩形</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%BB%98%E5%88%B6%E5%9C%86"><span class="toc-number">3.2.</span> <span class="toc-text">绘制圆</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%BB%98%E5%88%B6%E5%AD%97%E4%BD%93"><span class="toc-number">3.3.</span> <span class="toc-text">绘制字体</span></a></li></ol></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%B8%85%E7%A9%BA%E7%94%BB%E6%AD%A5%E5%92%8C%E6%B8%85%E9%99%A4%E6%8C%87%E5%AE%9A%E5%8C%BA%E5%9F%9F"><span class="toc-number">4.</span> <span class="toc-text">清空画步和清除指定区域</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E6%B8%85%E7%A9%BA%E7%94%BB%E5%B8%83"><span class="toc-number">4.1.</span> <span class="toc-text">清空画布</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E6%B8%85%E9%99%A4%E6%8C%87%E5%AE%9A%E5%8C%BA%E5%9F%9F"><span class="toc-number">4.2.</span> <span class="toc-text">清除指定区域</span></a></li></ol></li><li class="toc-item toc-level-3"><a class="toc-link" href="#canvas%E7%BB%98%E5%88%B6%E4%B8%80%E4%B8%AA%E6%9F%B1%E5%BD%A2%E5%9B%BE"><span class="toc-number">5.</span> <span class="toc-text">canvas绘制一个柱形图</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E6%95%88%E6%9E%9C"><span class="toc-number">5.1.</span> <span class="toc-text">效果</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E4%BB%A3%E7%A0%81"><span class="toc-number">5.2.</span> <span class="toc-text">代码</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E8%BF%87%E7%A8%8B%E5%9B%BE"><span class="toc-number">5.3.</span> <span class="toc-text">过程图</span></a></li></ol></li></ol></div></div><div class="card-widget card-recent-post"><div class="item-headline"><i class="fas fa-history"></i><span>最新文章</span></div><div class="aside-list"><div class="aside-list-item"><a class="thumbnail" href="/bbed5cd2.html" title="大家好我是夯大力,这是我的影视,大力金刚等系列"><img src="https://dreamos.oss-cn-beijing.aliyuncs.com/gitblog/202410091600476.png" onerror='this.onerror=null,this.src="/img/404.png"' alt="大家好我是夯大力,这是我的影视,大力金刚等系列"></a><div class="content"><a class="title" href="/bbed5cd2.html" title="大家好我是夯大力,这是我的影视,大力金刚等系列">大家好我是夯大力,这是我的影视,大力金刚等系列</a><time datetime="2024-10-21T08:12:21.000Z" title="发表于 2024-10-21 08:12:21">2024-10-21</time></div></div><div 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