HarmonyOS应用开发-绘制图像实现

说明：

从API version 7开始支持。后续版本如有新增内容，则采用上角标单独标记该内容的起始版本。

使用OffscreenCanvasRenderingContext2D在offscreen canvas上进行绘制，绘制对象可以是矩形、文本、图片等

属性：

示例代码：
Hml代码：

<div class="container">
    <canvas ref="canvasId" style="width: 500px; height: 500px; background-color: #ffff00;"></canvas>
</div>

Css代码：

.container {
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 100%;
    height: 100%;
}

Js代码：

export default {
    onShow(){
        var ctx = this.$refs.canvasId.getContext('2d');
        var offscreen = new OffscreenCanvas(360, 500);
        var offCanvas2 = offscreen.getContext("2d");
        var img = new Image();
        img.src = 'common/images/bg-tv.jpg';
        offCanvas2.drawImage(img, 0, 0, 100, 100);
        offCanvas2.filter = 'blur(5px)';
        offCanvas2.drawImage(img, 100, 0, 100, 100);

        offCanvas2.filter = 'grayscale(50%)';
        offCanvas2.drawImage(img, 200, 0, 100, 100);

        offCanvas2.filter = 'hue-rotate(90deg)';
        offCanvas2.drawImage(img, 0, 100, 100, 100);

        offCanvas2.filter = 'invert(100%)';
        offCanvas2.drawImage(img, 100, 100, 100, 100);

        offCanvas2.filter = 'drop-shadow(8px 8px 10px green)';
        offCanvas2.drawImage(img, 200, 100, 100, 100);

        offCanvas2.filter = 'brightness(0.4)';
        offCanvas2.drawImage(img, 0, 200, 100, 100);

        offCanvas2.filter = 'opacity(25%)';
        offCanvas2.drawImage(img, 100, 200, 100, 100);

        offCanvas2.filter = 'saturate(30%)';
        offCanvas2.drawImage(img, 200, 200, 100, 100);

        offCanvas2.filter = 'sepia(60%)';
        offCanvas2.drawImage(img, 0, 300, 100, 100);

        offCanvas2.filter = 'contrast(200%)';
        offCanvas2.drawImage(img, 100, 300, 100, 100);
        var bitmap = offscreen.transferToImageBitmap();
        ctx.transferFromImageBitmap(bitmap);
    }
}

实例效果：