CanvasContext

The CanvasContext is used for drawing onto the canvas. It is a subset of the HTML5 CanvasRenderingContext2D.

Import this type with “const {CanvasContext} = require('tabris');”

Methods

arc(x, y, radius, startAngle, endAngle, anticlockwise)

Parameters:

  • x: number
    • the x coordinate of the arc’s center.
  • y: number
    • the y coordinate of the arc’s center.
  • radius: number
    • the arc’s radius.
  • startAngle: number
    • the angle in radians at which the arc starts, measured clockwise from the positive x axis.
  • endAngle: number
    • the angle in radians at which the arc ends, measured clockwise from the positive x axis.
  • anticlockwise: boolean [Optional]
    • if true, causes the arc to be drawn counter-clockwise between the two angles.
      Adds an arc to the path which is centered at (x, y) position with radius r starting at startAngle and ending at endAngle going in the given direction by anticlockwise (defaulting to clockwise).

beginPath()

Starts a new path by emptying the list of sub-paths.

bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y)

Parameters:

  • cp1x: number
    • the x axis of the coordinate for the first control point.
  • cp1y: number
    • the y axis of the coordinate for the first control point.
  • cp2x: number
    • the x axis of the coordinate for the second control point.
  • cp2y: number
    • the y axis of the coordinate for the second control point.
  • x: number
    • the x axis of the coordinate for the end point.
  • y: number
    • the y axis of the coordinate for the end point.
      Adds a cubic Bézier curve to the path. The starting point is the last point in the current path.

clearRect(x, y, width, height)

Parameters:

  • x: number
    • the x axis of the rectangle’s upper-left corner.
  • y: number
    • the y axis of the rectangle’s upper-left corner.
  • width: number
    • the rectangle’s width.
  • height: number
    • the rectangles height.
      Sets all pixels in the rectangle defined by starting point (x, y) and size (width, height) to transparent, erasing any previously drawn content.

closePath()

Adds a straight line from the current point to the start of the current sub-path.

createImageData(width, height)

Parameters:

  • width: number
    • the width of the new ImageData object.
  • height: number
    • the height of the new ImageData object.
      Returns:ImageData

creates a new, blank ImageData object with the specified dimensions. All of the pixels in the new object are transparent black.

createImageData(imageData)

Parameters:

  • imageData: ImageData
    • an existing ImageData object from which to copy the width and height.
      Returns:ImageData

creates a new, blank ImageData object with the same dimensions as the specified existing ImageData object. All of the pixels in the new object are transparent black.

fill()

Fills the current or path with the current fill style.

fillRect(x, y, width, height)

Parameters:

  • x: number
    • the x axis of the rectangle’s upper-left corner.
  • y: number
    • the y axis of the rectangle’s upper-left corner.
  • width: number
    • the rectangle’s width.
  • height: number
    • the rectangles height.
      draws a filled rectangle at (x, y) position whose size is determined by width and height. and whose color is determined by the fillStyle attribute.

fillText(text, x, y)

Parameters:

  • text: string
    • the text to render.
  • x: number
    • the x axis of the coordinate for the text starting point.
  • y: number
    • the y axis of the coordinate for the text starting point.
      Fills a given text at the given (x, y) position using the current textAlign and textBaseline values.

getImageData(x, y, width, height)

Parameters:

  • x: number
    • the x axis of the rectangle’s upper-left corner.
  • y: number
    • the y axis of the rectangle’s upper-left corner.
  • width: number
    • the rectangle’s width.
  • height: number

Returns an ImageData object representing the underlying pixel data for the area of the canvas denoted by the given rectangle.

lineTo(x, y)

Parameters:

  • x: number
    • the x axis of the coordinate for the end of the line.
  • y: number
    • the y axis of the coordinate for the end of the line.
      Connects the last point in the sub-path to the (x, y) coordinates with a straight line.

moveTo(x, y)

Parameters:

  • x: number
    • the x axis of the point.
  • y: number
    • the y axis of the point.
      Moves the starting point of a new sub-path to the (x, y) coordinates.

putImageData(imageData, x, y)

Parameters:

  • imageData: ImageData
    • an ImageData object containing the array of pixel values.
  • x: number
    • x-coordinate of the upper-left corner of the image data rectangle
  • y: number
    • y-coordinate of the upper-left corner of the image data rectangle
      Paints data from the given ImageData object onto the bitmap at coordinates (x, y).

quadraticCurveTo(cpx, cpy, x, y)

Parameters:

  • cpx: number
    • the x axis of the coordinate for the control point.
  • cpy: number
    • the y axis of the coordinate for the control point.
  • x: number
    • the x axis of the coordinate for the end point.
  • y: number
    • the y axis of the coordinate for the end point.
      Adds a quadratic Bézier curve to the path. The starting point is the last point in the current path.

rect(x, y, width, height)

Parameters:

  • x: number
    • the x axis of the rectangle’s upper-left corner.
  • y: number
    • the y axis of the rectangle’s upper-left corner.
  • width: number
    • the rectangle’s width.
  • height: number
    • the rectangles height.
      Creates a path for a rectangle with the top-left corner at (x, y)

restore()

Restores the most recently saved canvas state by popping the top entry in the drawing state stack.

rotate(angle)

Parameters:

  • angle: number
    • The angle to rotate clockwise in radians.
      Adds a rotation to the transformation matrix.

save()

Saves the entire state of the canvas by pushing the current state onto a stack.

scale(x, y)

Parameters:

  • x: number
    • scaling factor in the horizontal direction.
  • y: number
    • scaling factor in the vertical direction.
      Adds a scaling transformation to the canvas units by x horizontally and by y vertically.

setTransform(a, b, c, d, e, f)

Parameters:

  • a: number
    • horizontal scaling.
  • b: number
    • horizontal skewing.
  • c: number
    • vertical skewing.
  • d: number
    • vertical scaling.
  • e: number
    • horizontal moving.
  • f: number
    • vertical moving.
      resets (overrides) the current transformation to the identity matrix and then invokes a transformation described by the arguments of this method. The matrix has the following format: [[a, c, e], [b, d, f], [0, 0, 1]]

stroke()

Strokes the current path with the current stroke style.

strokeRect(x, y, width, height)

Parameters:

  • x: number
    • the x axis of the rectangle’s upper-left corner.
  • y: number
    • the y axis of the rectangle’s upper-left corner.
  • width: number
    • the rectangle’s width.
  • height: number
    • the rectangles height.
      draws the outline of a rectangle at (x, y) position whose size is determined by width and height using the current stroke style.

strokeText(text, x, y)

Parameters:

  • text: string
    • the text to render.
  • x: number
    • the x axis of the coordinate for the text starting point.
  • y: number
    • the y axis of the coordinate for the text starting point.
      Strokes a given text at the given (x, y) position using the current textAlign and textBaseline values.

transform(a, b, c, d, e, f)

Parameters:

  • a: number
    • horizontal scaling.
  • b: number
    • horizontal skewing.
  • c: number
    • vertical skewing.
  • d: number
    • vertical scaling.
  • e: number
    • horizontal moving.
  • f: number
    • vertical moving.
      Multiplies the current transformation with the matrix described by the arguments of this method. The matrix has the following format: [[a, c, e], [b, d, f], [0, 0, 1]]

translate(x, y)

Parameters:

  • x: number
    • the distance to move in the horizontal direction.
  • y: number
    • the distance to move in the vertical direction.
      Adds a translation transformation by moving the canvas and its origin x horizontally and y vertically on the grid.

Properties

fillStyle

Type: Color

Specifies the color to use inside shapes.

font

Type: Font

Specifies the current text style being used when drawing text.

lineCap

Type: string, supported values: butt, round, square

Determines how the end points of every line are drawn.

lineJoin

Type: string, supported values: bevel, round, miter

Determines how two connecting segments in a shape are joined together.

lineWidth

Type: number

The thickness of lines in space units.

strokeStyle

Type: Color

Specifies the color to use for the lines around shapes.

textAlign

Type: string, supported values: left, right, center, start, end

Specifies the current text alignment being used when drawing text.

textBaseline

Type: string, supported values: top, hanging, middle, alphabetic, ideographic, bottom

Specifies the current text baseline being used when drawing text.

原文:

https://youjingyu.github.io/Tabris-Documention/?folderName=api&pageName=CanvasContext.html