• >HTML5畫布(Canvas)元素

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

  瀏覽器不支持畫布(canvas)時的備案

  <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');

• 圖形

  繪制方形

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

  填充區域

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

  繪制方形的邊框

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

  繪制圓形

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

• 風格

  填充

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

  勾勒

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

  線性漸變

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

  徑向漸變

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

  圖案

  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';

  交點

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

  線頭

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

  陰影

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

  Alpha (透明)

  context.globalAlpha = 0.5; // between 0 and 1

• 顏色格式

  字符串

  context.fillStyle = 'red';

  16進制

  context.fillStyle = '#ff0000';

  16進制簡寫

  context.fillStyle = '#f00';

  RGB

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

  RGBA

  context.fillStyle = 'rgba(255,0,0,1)';

• 路徑

  開始路徑

  context.beginPath();

  畫線

  context.lineTo(x, y);

  弧形

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

  二次曲線

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

  二次曲線

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

  關閉路徑

  context.closePath();

• 圖片

  畫圖

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

  指定尺寸畫圖

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

  裁剪圖片

  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

  寫文字

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

  寫鏤空文字

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

  粗體

  context.font = 'bold 40px Arial';

  斜體

  context.font = 'italic 40px Arial';

  對齊方式

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

  文字基線

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

  獲取文本寬度

  var width = context.measureText('Hello world').width;

• 動畫

  移動

  context.translate(x, y);

  擴大縮小

  context.scale(x, y);

  旋轉

  context.rotate(radians);

  水平翻轉

  context.scale(-1, 1);

  上下翻轉

  context.scale(1, -1);

  自定義變換

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

  設置變換

  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);

• 狀態存儲

  存儲

  context.save();

  恢復

  context.restore();

• 裁剪

  裁剪

  // draw path here context.clip();

• 圖像數據

  獲取圖像數據

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

  遍歷像素點

  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]; }

  沿坐標遍歷像素點

  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];} }

  設置圖像數據

  context.putImageData(imageData, x, y);

• DATA URLS

  獲取Data URL

  var dataURL = canvas.toDataURL();

  使用Data URL生成圖像

  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';

總結

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