HTML5 界面元素 Canvas 参考手册
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HTML5 界面元素 Canvas 参考手册
HTML Canvas Reference
描述
Description
The HTML5 <canvas> tag is used to draw graphics, on the fly, via scripting (usually JavaScript).
However, the <canvas> element has no drawing abilities of its own (it is only a container for graphics) - you must use a script to actually draw the graphics.
The getContext() method returns an object that provides methods and properties for drawing on the canvas.
This reference will cover the properties and methods of the getContext("2d") object, which can be used to draw text, lines, boxes, circles, and more - on the canvas.
浏览器支持
Browser Support
Internet Explorer 9, Firefox, Opera, Chrome, and Safari support <canvas> and its properties and methods.
Note: Internet Explorer 8 and earlier versions, do not support the <canvas> element.
颜色、样式和阴影
Colors, Styles, and Shadows
| Property | Description |
| fillStyle | Sets or returns the color, gradient, or pattern used to fill the drawing |
| strokeStyle | Sets or returns the color, gradient, or pattern used for strokes |
| shadowColor | Sets or returns the color to use for shadows |
| shadowBlur | Sets or returns the blur level for shadows |
| shadowOffsetX | Sets or returns the horizontal distance of the shadow from the shape |
| shadowOffsetY | Sets or returns the vertical distance of the shadow from the shape |
| Method | Description |
| createLinearGradient() | Creates a linear gradient (to use on canvas content) |
| createPattern() | Repeats a specified element in the specified direction |
| createRadialGradient() | Creates a radial/circular gradient (to use on canvas content) |
| addColorStop() | Specifies the colors and stop positions in a gradient object |
线条样式
Line Styles
| Property | Description |
| lineCap | Sets or returns the style of the end caps for a line |
| lineJoin | Sets or returns the type of corner created, when two lines meet |
| lineWidth | Sets or returns the current line width |
| miterLimit | Sets or returns the maximum miter length |
矩形
Rectangles
| Method | Description |
| rect() | Creates a rectangle |
| fillRect() | Draws a "filled" rectangle |
| strokeRect() | Draws a rectangle (no fill) |
| clearRect() | Clears the specified pixels within a given rectangle |
路径
Paths
| Method | Description |
| fill() | Fills the current drawing (path) |
| stroke() | Actually draws the path you have defined |
| beginPath() | Begins a path, or resets the current path |
| moveTo() | Moves the path to the specified point in the canvas, without creating a line |
| closePath() | Creates a path from the current point back to the starting point |
| lineTo() | Adds a new point and creates a line from that point to the last specified point in the canvas |
| clip() | Clips a region of any shape and size from the original canvas |
| quadraticCurveTo() | Creates a quadratic Bézier curve |
| bezierCurveTo() | Creates a cubic Bézier curve |
| arc() | Creates an arc/curve (used to create circles, or parts of circles) |
| arcTo() | Creates an arc/curve between two tangents |
| isPointInPath() | Returns true if the specified point is in the current path, otherwise false |
转换
Transformations
| Method | Description |
| scale() | Scales the current drawing bigger or smaller |
| rotate() | Rotates the current drawing |
| translate() | Remaps the (0,0) position on the canvas |
| transform() | Replaces the current transformation matrix for the drawing |
| setTransform() | Resets the current transform to the identity matrix. Then runs transform() |
文本
Text
| Property | Description |
| font | Sets or returns the current font properties for text content |
| textAlign | Sets or returns the current alignment for text content |
| textBaseline | Sets or returns the current text baseline used when drawing text |
| Method | Description |
| fillText() | Draws "filled" text on the canvas |
| strokeText() | Draws text on the canvas (no fill) |
| measureText() | Returns an object that contains the width of the specified text |
图像绘制
Image Drawing
| Method | Description |
| drawImage() | Draws an image, canvas, or video onto the canvas |
像素操作
Pixel Manipulation
| Property | Description |
| width | Returns the width of an ImageData object |
| height | Returns the height of an ImageData object |
| data | Returns an object that contains image data of a specified ImageData object |
| Method | Description |
| createImageData() | Creates a new, blank ImageData object |
| getImageData() | Returns an ImageData object that copies the pixel data for the specified rectangle on a canvas |
| putImageData() | Puts the image data (from a specified ImageData object) back onto the canvas |
混合
Compositing
| Property | Description |
| globalAlpha | Sets or returns the current alpha or transparency value of the drawing |
| globalCompositeOperation | Sets or returns how a new image are drawn onto an existing image |
其它
Other
| Method | Description |
| save() | Saves the state of the current context |
| restore() | Returns previously saved path state and attributes |
| createEvent() | |
| getContext() | |
| toDataURL() |