added OpenCV

package_lesson2/index.js

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+// 画布
+const canvas1 = 'canvas1'
+// 示例图片
+const sampleImage1 = './assets/sampleImage1.jpg'
+// 画布最大宽度
+const maxCanvasWidth = 375
+// wasm路径
+global.wasm_url = '/package_lesson2/assets/opencv3.4.16.wasm.br'
+// opencv_exec.js会从global.wasm_url获取wasm路径
+let cv = require('./assets/opencv_exec.js');
+
+Page({
+	// 画布的dom对象
+	canvasDom: null,
+	data: {
+		canvas1Width: 375,
+		canvas1Height: 150,
+		// 示例图片
+		sampleImage1Url: sampleImage1,
+	},
+	onReady() {
+		// 可见的画布
+		this.initCanvas(canvas1)
+	},
+	// 获取画布
+	initCanvas(canvasId) {
+		var _that = this;
+		wx.createSelectorQuery()
+			.select('#' + canvasId)
+			.fields({ node: true, size: true })
+			.exec((res) => {
+				const canvas2d = res[0].node;
+				// 设置画布的宽度和高度
+				canvas2d.width = res[0].width;
+				canvas2d.height = res[0].height;
+				_that.canvasDom = canvas2d
+			});
+	},
+	// 获取图像数据和调整图像大小
+	getImageData(image,offscreenCanvas) {
+		var _that = this
+		// const ctx = wx.createCanvasContext(canvasId);
+		var canvasWidth = image.width;
+		if (canvasWidth > maxCanvasWidth) {
+			canvasWidth = maxCanvasWidth;
+		}
+		// canvas Height
+		var canvasHeight = Math.floor(canvasWidth * (image.height / image.width));
+		// 离屏画布的宽度和高度不能小于图像的
+		offscreenCanvas.width = canvasWidth;
+		offscreenCanvas.height = canvasHeight;
+		// draw image on canvas
+		var ctx = offscreenCanvas.getContext('2d')
+		ctx.drawImage(image, 0, 0, canvasWidth, canvasHeight);
+		// get image data from canvas
+		var imgData = ctx.getImageData(0, 0, canvasWidth, canvasHeight);
+
+		return imgData
+	},
+	// 创建图像对象
+	async createImageElement(imgUrl) {
+		var _that = this
+		// 创建2d类型的离屏画布（需要微信基础库2.16.1以上）
+		var offscreenCanvas = wx.createOffscreenCanvas({type: '2d'});
+		const image = offscreenCanvas.createImage();
+		await new Promise(function (resolve, reject) {
+			image.onload = resolve
+			image.onerror = reject
+			image.src = imgUrl
+		})
+		const imageData = _that.getImageData(image,offscreenCanvas)
+		return imageData
+	},
+	imgProcess1(imageData, canvasDom) {
+		// 读取图像
+		let src = cv.imread(imageData);
+		let dst = new cv.Mat();
+		// 灰度化
+		cv.cvtColor(src, dst, cv.COLOR_RGBA2GRAY, 0);
+		// 显示图像
+		cv.imshow(canvasDom, dst);
+		// 回收对象
+		src.delete();
+		dst.delete()
+	},
+	imgProcess2(imageData, canvasDom) {
+		let src = cv.imread(imageData);
+		let dst = new cv.Mat();
+
+		// 灰度化
+		cv.cvtColor(src, src, cv.COLOR_RGBA2GRAY, 0);
+		// 边缘检测
+		cv.Canny(src, dst, 50, 100, 3, false);
+
+		cv.imshow(canvasDom, dst);
+		src.delete();
+		dst.delete()
+	},
+	imgProcess3(imageData, canvasDom) {
+		let src = cv.imread(imageData);
+		let dst = new cv.Mat();
+
+		// 灰度化
+		cv.cvtColor(src, src, cv.COLOR_RGBA2GRAY, 0);
+
+		var orb = new cv.ORB();
+		var keypoints = new cv.KeyPointVector();
+		var descriptors = new cv.Mat();
+		// 特征点
+		orb.detect(src, keypoints)
+		// 特征点的描述因子
+		orb.compute(src, keypoints, descriptors)
+		// 绘制特征点
+		cv.drawKeypoints(src, keypoints, dst)
+
+		cv.imshow(canvasDom, dst);
+		src.delete();
+		dst.delete()
+	},
+	async btnRun1() {
+		var _that = this;
+		// 将图像转换为ImageData
+		const image1Data = await _that.createImageElement(sampleImage1)
+		// 设置画布的显示大小
+		_that.setData({
+			canvas1Width: image1Data.width,
+			canvas1Height: image1Data.height,
+		})
+		_that.imgProcess1(image1Data, _that.canvasDom)
+	},
+	async btnRun2() {
+		// 同上
+		var _that = this;
+		const image1Data = await _that.createImageElement(sampleImage1)
+		_that.setData({
+			canvas1Width: image1Data.width,
+			canvas1Height: image1Data.height,
+		})
+		_that.imgProcess2(image1Data, _that.canvasDom)
+	},
+	async btnRun3() {
+		// 同上
+		var _that = this;
+		const image1Data = await _that.createImageElement(sampleImage1)
+		_that.setData({
+			canvas1Width: image1Data.width,
+			canvas1Height: image1Data.height,
+		})
+		_that.imgProcess3(image1Data, _that.canvasDom)
+	},
+})