harmony 鸿蒙Path2D

2022-08-09
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Path2D

<Path2D> allows you to describe a path through an existing path. This path can be drawn through the stroke API of Canvas. For details, see Path2D.

Drawing Line Segments

Create a <Path2D> object and use line segments to create different shapes.

<!-- xxx.hml --> 
<div class="container">
  <canvas ref="canvas"></canvas>
</div>

/* xxx.css */
.container {
    flex-direction: column;
    background-color: #F1F3F5;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
}

canvas {
    width: 600px;
    height: 600px;
    background-color: #fdfdfd;
    border: 5px solid red;
}

// xxx.js
import promptAction from '@ohos.promptAction';

export default {
    onShow() {
        let ctx = this.$refs.canvas.getContext('2d', {
            antialias: true
        });
        let path = ctx.createPath2D();
        // Roof
        path.moveTo(10, 300);
        path.lineTo(210, 100);
        path.lineTo(410, 300);
        // House
        path.moveTo(10, 300);
        path.lineTo(410, 300);
        path.lineTo(410, 600);
        path.lineTo(10, 600);
        path.closePath();
        // Window
        path.moveTo(50, 450);
        path.bezierCurveTo(70, 350, 130, 350, 150, 450);
        path.closePath();
        // Door
        path.moveTo(250, 450);
        path.rect(250, 450, 100, 600);
        path.closePath();
        // Chimney
        path.moveTo(365, 250);
        path.ellipse(310, 215, 30, 130, 0, Math.PI * 0.04, Math.PI * 1.1, 1);
        // Tree
        path.moveTo(485, 450);
        path.quadraticCurveTo(510, 500, 485, 600);
        path.moveTo(550, 450);
        path.quadraticCurveTo(525, 500, 550, 600);
        path.moveTo(600, 535);
        path.arc(520, 450, 85, 0, 6);
        ctx.stroke(path);
    }
}

en-us_image_0000001232002968

Drawing Graphs

Use createPath2D to create a path object and draw only path1 so that only path1 is displayed on the canvas. Click the Text component to trigger the addPath method. The path2 object is passed to path1 as a parameter. After the stroke operation is performed on the path1 object, path1 and path2 are displayed on the canvas. Click Change to change the value of setTransform to** setTransform(2, 0.1, 0.1, 2, 0,0)**. The graph is enlarged and tilted to the left.

<!-- xxx.hml -->
<div class="container">
    <canvas ref="canvas"></canvas>
    <div class="content">
        <text onclick="addPath">{{ isAdd }}</text>
        <text onclick="setTransform">{{ textName }}</text>
    </div>
</div>

/* xxx.css */
.container {
    flex-direction: column;
    background-color: #F1F3F5;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
}

canvas {
    width: 600px;
    height: 600px;
    background-color: #fdfdfd;
    border: 5px solid red;
}

.content {
    width: 80%;
    margin-top: 50px;
    margin-bottom: 50px;
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
}

text {
    width: 150px;
    height: 80px;
    color: white;
    border-radius: 20px;
    text-align: center;
    background-color: #6060e7;
    margin-bottom: 30px;
}

// xxx.js
import promptAction from '@ohos.promptAction';

export default {
    data: {
        ctx: null,
        path1: null,
        path2: null,
        path3: null,
        isAdd: "addPath2",
        isChange: true,
        textName: 'change'
    },
    onShow() {
        this.ctx = this.$refs.canvas.getContext('2d', {
            antialias: true
        });
        this.path1 = this.ctx.createPath2D();
        // Square
        this.path1.moveTo(200, 200);
        this.path1.lineTo(400, 200);
        this.path1.lineTo(400, 400);
        this.path1.lineTo(200, 400);
        this.path1.closePath();
        this.path2 = this.ctx.createPath2D();
        // Arc
        this.path2.arc(300, 300, 75, 0, 6.28);
        this.ctx.stroke(this.path1);
    },
    addPath() {
        if (this.isAdd == "addPath2") {
            // Clear the content in the specified area on the canvas.
            this.ctx.clearRect(0, 0, 600, 600);
            this.ctx.beginPath();
            // Add a path to the current path.
            this.path2.addPath(this.path1);
            this.ctx.stroke(this.path2);
            this.isAdd = "clearPath2";
        } else {
            this.ctx.clearRect(0, 0, 600, 600);
            this.ctx.stroke(this.path1);
            this.isAdd = "addPath2";
        }
    },
    setTransform() {
        if (this.isChange) {
            this.ctx.clearRect(0, 0, 600, 600);
            this.path3 = this.ctx.createPath2D();
            this.path3.arc(150, 150, 100, 0, 6.28);
            // Reset and create a new transformation matrix.
            this.path3.setTransform(2, 0.1, 0.1, 2, 0, 0);
            this.ctx.stroke(this.path3);
            this.isChange = !this.isChange;
            this.textName = "back"
        } else {
            this.ctx.clearRect(0, 0, 600, 600);
            this.path3.setTransform(0.5, -0.1, -0.1, 0.5, 0, 0);
            this.ctx.stroke(this.path3);
            this.isChange = !this.isChange;
            this.textName = "change";
        }
    }
}

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