HTML5画布(CANVAS)速查简表

  • HTML5画布(CANVAS)元素

    >HTML5画布(Canvas)元素

    <canvas id="myCanvas" width="500" height="300">
    

    浏览器不支持画布(canvas)时的备案

    <canvas id="myCanvas" width="500" height="300">
      your browser doesn‘t support canvas!
    </canvas>
    

    2d context

    var context = canvas.getContext(‘2d‘);
    

    Webgl context (3d)

    var context = canvas.getContext(‘webgl‘);
    
  • 图形

    绘制方形

    context.rect(x, y, width, height);
    context.fill();
    context.stroke();
    

    填充区域

    context.fillRect(x, y, width, height);
    

    绘制方形的边框

    context.strokeRect(x, y, width, height);
    

    绘制圆形

    context.arc(x, y, radius, 0, Math.PI * 2);
    context.fill();
    context.stroke();
    
  • 风格

    填充

    context.fillStyle = ‘red‘;
    context.fill();
    

    勾勒

    context.strokeStyle = ‘red‘;
    context.stroke();
    

    线性渐变

    var grd = context.createLinearGradient(x1, y1, x2, y2);
    grd.addColorStop(0, ‘red‘);   
    grd.addColorStop(1, ‘blue‘);
    context.fillStyle = grd;
    context.fill();
    

    径向渐变

    var grd = context.createRadialGradient(x1, y1, radius1, x2, y2, radius2);
    grd.addColorStop(0, ‘red‘);
    grd.addColorStop(1, ‘blue‘);
    context.fillStyle = grd;
    context.fill();
    

    图案

    var imageObj = new Image();
    imageObj.onload = function() {
      var pattern = context.createPattern(imageObj, ‘repeat‘);
      context.fillStyle = pattern;
      context.fill();
    };
    imageObj.src = ‘path/to/my/image.jpg‘;
    

    交点

    context.lineJoin = ‘miter|round|bevel‘;
    

    线头

    context.lineCap = ‘butt|round|square‘;
    

    阴影

    context.shadowColor = ‘black‘;
    context.shadowBlur = 20;
    context.shadowOffsetX = 10;
    context.shadowOffsetY = 10;
    

    Alpha (透明)

    context.globalAlpha = 0.5; // between 0 and 1
    
  • 颜色格式

    字符串

    context.fillStyle = ‘red‘;
    

    16进制

    context.fillStyle = ‘#ff0000‘;
    

    16进制简写

    context.fillStyle = ‘#f00‘;
    

    RGB

    context.fillStyle = ‘rgb(255,0,0)‘;
    

    RGBA

    context.fillStyle = ‘rgba(255,0,0,1)‘;
    
  • 路径

    开始路径

    context.beginPath();
    

    画线

    context.lineTo(x, y);
    

    弧形

    context.arc(x, y, radius, startAngle, endAngle, counterClockwise);
    

    二次曲线

    context.quadraticCurveTo(cx, cy, x, y);
    

    二次曲线

    context.bezierCurveTo(cx1, cy1, cx2, cy2, x, y);
    

    关闭路径

    context.closePath();
    
  • 图片

    画图

    var imageObj = new Image();
    imageObj.onload = function() {
      context.drawImage(imageObj, x, y);
    };
    imageObj.src = ‘path/to/my/image.jpg‘;
    

    指定尺寸画图

    var imageObj = new Image();
    imageObj.onload = function() {
      context.drawImage(imageObj, x, y, width, height);
    };
    imageObj.src = ‘path/to/my/image.jpg‘;
    

    裁剪图片

    var imageObj = new Image();
    imageObj.onload = function() {
      context.drawImage(imageObj, sx, sy, sw, sh, dx, dy, dw, dh);
    };
    imageObj.src = ‘path/to/my/image.jpg‘;
    
  • 文本

    写文字

    context.font = ‘40px Arial‘;
    context.fillStyle = ‘red‘;
    context.fillText(‘Hello World!‘, x, y);
    

    写镂空文字

    context.font = ‘40pt Arial‘;
    context.strokeStyle = ‘red‘;
    context.strokeText(‘Hello World!‘, x, y);
    

    粗体

    context.font = ‘bold 40px Arial‘;
    

    斜体

    context.font = ‘italic 40px Arial‘;
    

    对齐方式

    context.textAlign = ‘start|end|left|center|right‘;
    

    文字基线

    context.textBaseline = ‘top|hanging|middle|alphabetic|ideographic
    |bottom‘;
    

    获取文本宽度

    var width = context.measureText(‘Hello world‘).width;
    
  • 动画

    移动

    context.translate(x, y);
    

    扩大缩小

    context.scale(x, y);
    

    旋转

    context.rotate(radians);
    

    水平翻转

    context.scale(-1, 1);
    

    上下翻转

    context.scale(1, -1);
    

    自定义变换

    context.transform(a, b, c, d ,e, f);
    

    设置变换

    context.setTransform(a, b, c, d ,e, f);
    

    切割

    context.transform(1, sy, sx, 1, 0, 0);
    

    重置

    context.setTransform(1, 0, 0, 1, 0, 0);
    
  • 状态存储

    存储

    context.save();
    

    恢复

    context.restore();
    
  • 裁剪

    裁剪

    // draw path here
    context.clip();
    
  • 图像数据

    获取图像数据

    var imageData = context.getImageData(x, y, width, height);
    var data = imageData.data;
    

    遍历像素点

    var imageData = context.getImageData(x, y, width, height);
    var data = imageData.data;
    var len = data.length;
    var i, red, green, blue, alpha;
    
    for(i = 0; i < len; i += 4) {
      red = data[i];
      green = data[i + 1];
      blue = data[i + 2];
      alpha = data[i + 3];
    }
    

    沿坐标遍历像素点

    var imageData = context.getImageData(x, y, width, height);
    var data = imageData.data;
    var x, y, red, green, blue, alpha;
    
    for(y = 0; y < imageHeight; y++) {
      for(x = 0; x < imageWidth; x++) {
        red = data[((imageWidth * y) + x) * 4];
        green = data[((imageWidth * y) + x) * 4 + 1];
        blue = data[((imageWidth * y) + x) * 4 + 2];
        alpha = data[((imageWidth * y) + x) * 4 + 3];
      }
    }
    

    设置图像数据

    context.putImageData(imageData, x, y);
    
  • DATA URLS

    获取Data URL

    var dataURL = canvas.toDataURL();
    

    使用Data URL生成图像

    var imageObj = new Image();
    imageObj.onload = function() {
      context.drawImage(imageObj, 0, 0);
    };
    
    imageObj.src = dataURL;
    
  • 合成

    合成操作

    context.globalCompositeOperation = ‘source-atop|source-in|source-out|source-over|destination-atop|destination-in|destination-out|destination-over|lighter|xor|copy‘;
    
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