Implementation of scratch card in WeChat mini program

How to achieve the effect of scratch card?

The idea is:

1. First determine the position and size of the winning picture or text

2. Start drawing the canvas, and match the position and size to the previous winning copy. The location remains consistent.

3. Cover the canvas with a gray mask to create the effect of the scratch card before it is scratched

The specific code is as follows

let left=0;
this.data.awardCanvas.moveTo(left,0)
this.data.awardCanvas.lineTo(left+400,0);
this.data.awardCanvas.lineTo(left+400,150);
this.data.awardCanvas.lineTo(left,150);
this.data.awardCanvas.stroke()
this.data.awardCanvas.setFillStyle('#ddd')
this.data.awardCanvas.fill()
this.data.awardCanvas.draw()

4. Start To make a scratch card action, define two triggered actions, bindtouchstart and bindtouchmove, on canvas

bindtouchstart is the first position where the finger starts to fall, and bindtouchmove is the position where the finger moves

One of the important canvas attributes is clearRect, which clears the content on the canvas

clearRect (clears the X coordinate of the position, clears the Y coordinate of the position, clears the width, clears the height)

The specific code is as follows ：

this.data.awardCanvas.clearRect(x,y,15,15);
this.data.awardCanvas.draw(true)

The specific code is athttps://github.com/zhaodengping/scratch-mini

Go and try it, maybe You can win the first prize~~

Recommended tutorial: "WeChat Mini Program"

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