HTML -Canvas- Referenz
Beschreibung
Das HTML5-<canvas>-Tag wird verwendet, um Grafiken im Handumdrehen über Skripte (normalerweise JavaScript) zu zeichnen.
Das <canvas>-Element hat jedoch keine eigenen Zeichenfähigkeiten (es ist nur ein Container für Grafiken) – Sie müssen ein Skript verwenden, um die Grafiken tatsächlich zu zeichnen.
Die Methode getContext() gibt ein Objekt zurück, das Methoden und Eigenschaften zum Zeichnen auf der Zeichenfläche bereitstellt.
Diese Referenz behandelt die Eigenschaften und Methoden des getContext("2d")-Objekts, das zum Zeichnen von Text, Linien, Kästchen, Kreisen und mehr auf der Leinwand verwendet werden kann.
Browser-Unterstützung
Die Zahlen in der Tabelle geben die erste Browserversion an, die das Element vollständig unterstützt.
Element |
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<canvas> |
4.0 |
9.0 |
2.0 |
3.1 |
9.0 |
Internet Explorer 9, Firefox, Opera, Chrome und Safari unterstützen <canvas> und seine Eigenschaften und Methoden.
Hinweis: Internet Explorer 8 und frühere Versionen unterstützen das <canvas>-Element nicht.
Farben, Stile und Schatten
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 |
Linienstile
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 |
Rechtecke
Pfade
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 to that point from 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 |
Transformationen
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() |
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 |
Bildzeichnung
Method |
Description |
drawImage() |
Draws an image, canvas, or video onto the canvas |
Pixelmanipulation
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 |
Zusammensetzen
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 |
Andere
Method |
Description |
save() |
Saves the state of the current context |
restore() |
Returns previously saved path state and attributes |
createEvent() |
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getContext() |
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toDataURL() |
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