openCV常用操作

const cv = require('opencv4nodejs');

創(chuàng)建矩陣

const rows = 100; // height
const cols = 100; // width

var emptyMat = new cv.Mat(rows, cols, cv.CV_8UC3);
8位無符號(hào)3通道矩陣,就是常見的RGB數(shù)組[0-255,0-255,0-255]

var whiteMat = new cv.Mat(rows, cols, cv.CV_8UC1, 255);
var blueMat = new cv.Mat(rows, cols, cv.CV_8UC3, [255, 0, 0]);

  • 使用Array創(chuàng)建
    const matData = [
    [[255, 0, 0], [255, 0, 0], [255, 0, 0]],
    [[0, 0, 0], [0, 0, 0], [0, 0, 0]],
    [[255, 0, 0], [255, 0, 0], [255, 0, 0]]
    ];
    var matFromArray = new cv.Mat(matData, cv.CV_8UC3);

  • 使用Buffer創(chuàng)建
    const charData = [255, 0, ...];
    const matFromArray = new cv.Mat(Buffer.from(charData), rows, cols, cv.CV_8UC3);

  • 創(chuàng)建一個(gè)點(diǎn)
    const pt2 = new cv.Point(100, 100);
    const pt3 = new cv.Point(100, 100, 0.5);

  • 創(chuàng)建一個(gè)向量
    const vec2 = new cv.Vec(100, 100);
    const vec3 = new cv.Vec(100, 100, 0.5);
    const vec4 = new cv.Vec(100, 100, 0.5, 0.5);

矩陣、向量操作

const mat0 = new cv.Mat(...);
const mat1 = new cv.Mat(...);

  • 四則運(yùn)算
    const matMultipliedByScalar = mat0.mul(0.5); 標(biāo)量乘法
    const matDividedByScalar = mat0.div(2); 標(biāo)量除法
    const mat0PlusMat1 = mat0.add(mat1); 矩陣加法
    const mat0MinusMat1 = mat0.sub(mat1); 矩陣減法
    const mat0MulMat1 = mat0.hMul(mat1); 矩陣乘法
    const mat0DivMat1 = mat0.hDiv(mat1); 矩陣除法

  • 矩陣邏輯運(yùn)算操作
    const mat0AndMat1 = mat0.and(mat1);
    const mat0OrMat1 = mat0.or(mat1);
    const mat0bwAndMat1 = mat0.bitwiseAnd(mat1);
    const mat0bwOrMat1 = mat0.bitwiseOr(mat1);
    const mat0bwXorMat1 = mat0.bitwiseXor(mat1);
    const mat0bwNot = mat0.bitwiseNot();

訪問矩陣、向量數(shù)據(jù)

const matBGR = new cv.Mat(..., cv.CV_8UC3);
const matGray = new cv.Mat(..., cv.CV_8UC1);

  • 獲取到像素點(diǎn)的值
    const vec3 = matBGR.at(200, 100);
    const grayVal = matGray.at(200, 100);

  • 使用解構(gòu)賦值語法獲取值
    const [b, g, r] = matBGR.atRaw(200, 100);

  • 設(shè)置單個(gè)像素點(diǎn)的值
    matBGR.set(50, 50, [255, 0, 0]);
    matBGR.set(50, 50, new Vec(255, 0, 0));
    matGray.set(50, 50, 255);

  • 得到一個(gè)偏移量為( 50, 50)矩陣區(qū)域的25x25的小區(qū)域
    const width = 25;
    const height = 25;
    const region = matBGR.getRegion(new cv.Rect(50, 50, width, height));
    const matAsBuffer = matBGR.getData();
    const matAsArray = matBGR.getDataAsArray();

IO

  • 讀取圖片
    const mat = cv.imread('./path/img.jpg');
    cv.imreadAsync('./path/img.jpg', (err, mat) => {})

  • 保存圖片
    cv.imwrite('./path/img.png', mat);
    cv.imwriteAsync('./path/img.jpg', mat,(err) => {})

  • 展示圖片
    cv.imshow('a window name', mat);
    cv.waitKey();

  • 加載base64編碼的圖片
    const base64text='data:image/png;base64,R0lGO..'; //base64字符串
    const base64data =base64text.replace('data:image/jpeg;base64','')

const buffer = Buffer.from(base64data,'base64');
const image = cv.imdecode(buffer);

  • 轉(zhuǎn)換矩陣為base64編碼的圖片
    const outBase64 = cv.imencode('.jpg', croppedImage).toString('base64');
    const htmlImg='<img src=data:image/jpeg;base64,'+outBase64 + '>'; //Create insert into HTML compatible <img> tag

  • 捕獲webcam資源
    const devicePort = 0;
    const wCap = new cv.VideoCapture(devicePort);

  • 捕獲視頻資源
    const vCap = new cv.VideoCapture('./path/video.mp4');

  • 讀取幀
    const frame = vCap.read();
    vCap.readAsync((err, frame) => {});

  • 循環(huán)獲取
    const delay = 10;
    let done = false;
    while (!done) {
    ? let frame = vCap.read();
    ? if (frame.empty) {
    ? ? vCap.reset();
    ? ? frame = vCap.read();
    ? }
    ? ? const key = cv.waitKey(delay);
    ? ? done = key !== 255;
    }

  • 類型轉(zhuǎn)換
    const matSignedInt = matBGR.convertTo(cv.CV_32SC3);
    const matDoublePrecision = matBGR.convertTo(cv.CV_64FC3);

  • 轉(zhuǎn)換顏色制度
    const matGray = matBGR.bgrToGray();
    const matHSV = matBGR.cvtColor(cv.COLOR_BGR2HSV);
    const matLab = matBGR.cvtColor(cv.COLOR_BGR2Lab);

  • 調(diào)整矩陣大小
    const matHalfSize = matBGR.rescale(0.5);
    const mat100x100 = matBGR.resize(100, 100);
    const matMaxDimIs100 = matBGR.resizeToMax(100);

  • 獲取通道、通過通道構(gòu)建矩陣
    const [matB, matG, matR] = matBGR.splitChannels();
    const matRGB = new cv.Mat([matR, matB, matG]);

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