HTML DOM Canvas -object
Canvasobject
De HTML5 <canvas>-tag wordt gebruikt om afbeeldingen te tekenen, on-the-fly, met JavaScript.
Een canvasobject openen
U kunt toegang krijgen tot een <canvas>-element met getElementById():
Voorbeeld
var x = document.getElementById("myCanvas");
Een canvasobject maken
U kunt een <canvas>-element maken door de methode document.createElement() te gebruiken:
Voorbeeld
var x = document.createElement("CANVAS");
Opmerking: het <canvas>-element heeft geen eigen tekenmogelijkheden (het is alleen een container voor afbeeldingen) - u moet een script gebruiken om de afbeeldingen daadwerkelijk te tekenen.
De methode getContext() retourneert een object dat methoden en eigenschappen biedt om op het canvas te tekenen.
Deze referentie behandelt de eigenschappen en methoden van het object getContext("2d"), dat kan worden gebruikt om tekst, lijnen, kaders, cirkels en meer op het canvas te tekenen.
Kleuren, stijlen en schaduwen
| 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 |
Lijnstijlen
| 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 |
rechthoeken
Paden
| 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 |
Transformaties
| 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() |
Tekst
| 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 |
Afbeeldingstekening
| Method |
Description |
| drawImage() |
Draws an image, canvas, or video onto the canvas |
Pixelmanipulatie
| 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 |
compositie
| 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 |
Ander
| Method |
Description |
| save() |
Saves the state of the current context |
| restore() |
Returns previously saved path state and attributes |
| createEvent() |
|
| getContext() |
|
| toDataURL() |
|
Standaard eigenschappen en evenementen
Het canvasobject ondersteunt ook de standaardeigenschappen en gebeurtenissen .
Gerelateerde pagina's
HTML-zelfstudie: HTML5 Canvas
HTML-referentie: HTML <canvas>-tag
