harmony 鸿蒙canvas

2022-08-09
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canvas

NOTE

This component is supported since API version 4. Updates will be marked with a superscript to indicate their earliest API version.

The <canvas> component is used for customizing drawings.

Required Permissions

None

Child Components

Not supported

Attributes

The universal attributes are supported.

Styles

The universal styles are supported.

Events

The universal events are supported.

Methods

In addition to the universal methods, the following methods are supported.

getContext

getContext(type: ‘2d’, options?: ContextAttrOptions): CanvasRenderingContext2D

Obtains the canvas drawing context. This API cannot be called in onInit or onReady.

Parameters

Name	Type	Mandatory	Description
type	string	Yes	Object type. The value is set to ‘2d’, indicating that a 2D drawing object is returned. This object can be used to draw rectangles, texts, and images on the canvas component.
options⁶⁺	ContextAttrOptions	No	Whether to enable anti-aliasing. By default, anti-aliasing is disabled.

Table 1 ContextAttrOptions

Name	Type	Description
antialias	boolean	Whether to enable anti-aliasing. The default value is false.

Return value

Type	Description
CanvasRenderingContext2D	2D drawing object, which can be used to draw rectangles, images, and texts on the canvas component.

toDataURL⁶⁺

toDataURL(type?: string, quality?: number): string

Generates a URL containing image display information.

Parameters

Name	Type	Mandatory	Description
type	string	No	Image format. The default value is image/png.
quality	number	No	Image quality, which ranges from 0 to 1, when the image format is image/jpeg or image/webp. If the set value is beyond the value range, the default value 0.92 is used.

Return value

Type	Description
string	Image URL.

Example

<!-- xxx.hml -->
<div>
  <canvas ref="canvas1" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
  <input type="button" style="width: 180px; height: 60px;" value="fillStyle" onclick="handleClick" />
</div>

// xxx.js
export default {
  handleClick() {
    const el = this.$refs.canvas1;
    var dataURL = el.toDataURL();
    console.log(dataURL);
    // "data:image/png;base64,xxxxxxxx..."
  }
}