Oggetto HTML DOM Canvas
Oggetto Tela
Il tag HTML5 <canvas> viene utilizzato per disegnare grafici, al volo, con JavaScript.
Accedi a un oggetto Canvas
Puoi accedere a un elemento <canvas> usando getElementById():
Esempio
var x = document.getElementById("myCanvas");
Crea un oggetto Canvas
È possibile creare un elemento <canvas> utilizzando il metodo document.createElement():
Esempio
var x = document.createElement("CANVAS");
Nota: l'elemento <canvas> non ha capacità di disegno proprie (è solo un contenitore per la grafica) - devi usare uno script per disegnare effettivamente la grafica.
Il metodo getContext() restituisce un oggetto che fornisce metodi e proprietà per disegnare sull'area di disegno.
Questo riferimento tratterà le proprietà e i metodi dell'oggetto getContext("2d"), che può essere utilizzato per disegnare testo, linee, riquadri, cerchi e altro ancora sull'area di lavoro.
Colori, stili e ombre
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 |
Stili di linea
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 |
Rettangoli
Percorsi
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 |
Trasformazioni
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() |
Testo
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 |
Disegno dell'immagine
Method |
Description |
drawImage() |
Draws an image, canvas, or video onto the canvas |
Manipolazione dei pixel
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 |
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 |
Altro
Method |
Description |
save() |
Saves the state of the current context |
restore() |
Returns previously saved path state and attributes |
createEvent() |
|
getContext() |
|
toDataURL() |
|
Proprietà ed eventi standard
L'oggetto canvas supporta anche le proprietà e gli eventi standard .
Pagine correlate
Esercitazione HTML: Tela HTML5
Riferimento HTML: tag HTML <canvas>