javascript - 构建 opencv.js 时如何包含 cv.imread()？

Question

我克隆了 OpenCV Git 存储库:git clone https://github.com/opencv/opencv.git并没有改变任何东西。

然后我跟着build opencv.js关于 OpenCV 的逐步文档 https://docs.opencv.org/4.5.2/d4/da1/tutorial_js_setup.html并成功构建了opencv.js和 tests用命令

python ./platforms/js/build_js.py build_js --build_test

然后我用一个实时服务器打开了创建的test.html并看到所有测试均成功:"581 assertions of 581 passed, 0 failed."

但是当我插入内置的 opencv.js在 <script> </script> 之间标签并使用它，它仍然有效，除了 cv.imread() .我收到错误消息:`

"Uncaught TypeError: cv.imread is not a function".`

这是代码块:

let canvas = document.getElementById("canvas");
let ctx = canvas.getContext("2d");
let matrix = cv.imread("canvas");

然后我使用了官方的opencv.js 和imread() 工作。然而，问题是 opencv.js 的大小为 7.7 mb，因为它包含了 OpenCV 的大部分功能，而我只需要一些核心和图像处理功能。

如何将 imread() 包含在构建中？到目前为止我找不到解决方案。我只找到了构建白名单:它位于 OpenCV 存储库中，名称为 opencv_js.config.py，包括以下内容。知道如何将 imread() 包含在构建中吗？因为 OpenCV JavaScript 文档几乎在每个示例中都使用 imread()，所以应该有一种简单的方法来包含它。

# Classes and methods whitelist

core = {
    '': [
        'absdiff', 'add', 'addWeighted', 'bitwise_and', 'bitwise_not', 'bitwise_or', 'bitwise_xor', 'cartToPolar',
        'compare', 'convertScaleAbs', 'copyMakeBorder', 'countNonZero', 'determinant', 'dft', 'divide', 'eigen',
        'exp', 'flip', 'getOptimalDFTSize','gemm', 'hconcat', 'inRange', 'invert', 'kmeans', 'log', 'magnitude',
        'max', 'mean', 'meanStdDev', 'merge', 'min', 'minMaxLoc', 'mixChannels', 'multiply', 'norm', 'normalize',
        'perspectiveTransform', 'polarToCart', 'pow', 'randn', 'randu', 'reduce', 'repeat', 'rotate', 'setIdentity', 'setRNGSeed',
        'solve', 'solvePoly', 'split', 'sqrt', 'subtract', 'trace', 'transform', 'transpose', 'vconcat',
        'setLogLevel', 'getLogLevel',
    ],
    'Algorithm': [],
}

imgproc = {'': ['Canny', 'GaussianBlur', 'Laplacian', 'HoughLines', 'HoughLinesP', 'HoughCircles', 'Scharr','Sobel', \
                'adaptiveThreshold','approxPolyDP','arcLength','bilateralFilter','blur','boundingRect','boxFilter',\
                'calcBackProject','calcHist','circle','compareHist','connectedComponents','connectedComponentsWithStats', \
                'contourArea', 'convexHull', 'convexityDefects', 'cornerHarris','cornerMinEigenVal','createCLAHE', \
                'createLineSegmentDetector','cvtColor','demosaicing','dilate', 'distanceTransform','distanceTransformWithLabels', \
                'drawContours','ellipse','ellipse2Poly','equalizeHist','erode', 'filter2D', 'findContours','fitEllipse', \
                'fitLine', 'floodFill','getAffineTransform', 'getPerspectiveTransform', 'getRotationMatrix2D', 'getStructuringElement', \
                'goodFeaturesToTrack','grabCut','initUndistortRectifyMap', 'integral','integral2', 'isContourConvex', 'line', \
                'matchShapes', 'matchTemplate','medianBlur', 'minAreaRect', 'minEnclosingCircle', 'moments', 'morphologyEx', \
                'pointPolygonTest', 'putText','pyrDown','pyrUp','rectangle','remap', 'resize','sepFilter2D','threshold', \
                'undistort','warpAffine','warpPerspective','warpPolar','watershed', \
                'fillPoly', 'fillConvexPoly', 'polylines',
    ],
    'CLAHE': ['apply', 'collectGarbage', 'getClipLimit', 'getTilesGridSize', 'setClipLimit', 'setTilesGridSize'],
    'segmentation_IntelligentScissorsMB': [
        'IntelligentScissorsMB',
        'setWeights',
        'setGradientMagnitudeMaxLimit',
        'setEdgeFeatureZeroCrossingParameters',
        'setEdgeFeatureCannyParameters',
        'applyImage',
        'applyImageFeatures',
        'buildMap',
        'getContour'
    ],
}

objdetect = {'': ['groupRectangles'],
             'HOGDescriptor': ['load', 'HOGDescriptor', 'getDefaultPeopleDetector', 'getDaimlerPeopleDetector', 'setSVMDetector', 'detectMultiScale'],
             'CascadeClassifier': ['load', 'detectMultiScale2', 'CascadeClassifier', 'detectMultiScale3', 'empty', 'detectMultiScale'],
             'QRCodeDetector': ['QRCodeDetector', 'decode', 'decodeCurved', 'detect', 'detectAndDecode', 'detectMulti', 'setEpsX', 'setEpsY']}

video = {'': ['CamShift', 'calcOpticalFlowFarneback', 'calcOpticalFlowPyrLK', 'createBackgroundSubtractorMOG2', \
             'findTransformECC', 'meanShift'],
         'BackgroundSubtractorMOG2': ['BackgroundSubtractorMOG2', 'apply'],
         'BackgroundSubtractor': ['apply', 'getBackgroundImage']}

dnn = {'dnn_Net': ['setInput', 'forward'],
       '': ['readNetFromCaffe', 'readNetFromTensorflow', 'readNetFromTorch', 'readNetFromDarknet',
            'readNetFromONNX', 'readNet', 'blobFromImage']}

features2d = {'Feature2D': ['detect', 'compute', 'detectAndCompute', 'descriptorSize', 'descriptorType', 'defaultNorm', 'empty', 'getDefaultName'],
              'BRISK': ['create', 'getDefaultName'],
              'ORB': ['create', 'setMaxFeatures', 'setScaleFactor', 'setNLevels', 'setEdgeThreshold', 'setFirstLevel', 'setWTA_K', 'setScoreType', 'setPatchSize', 'getFastThreshold', 'getDefaultName'],
              'MSER': ['create', 'detectRegions', 'setDelta', 'getDelta', 'setMinArea', 'getMinArea', 'setMaxArea', 'getMaxArea', 'setPass2Only', 'getPass2Only', 'getDefaultName'],
              'FastFeatureDetector': ['create', 'setThreshold', 'getThreshold', 'setNonmaxSuppression', 'getNonmaxSuppression', 'setType', 'getType', 'getDefaultName'],
              'AgastFeatureDetector': ['create', 'setThreshold', 'getThreshold', 'setNonmaxSuppression', 'getNonmaxSuppression', 'setType', 'getType', 'getDefaultName'],
              'GFTTDetector': ['create', 'setMaxFeatures', 'getMaxFeatures', 'setQualityLevel', 'getQualityLevel', 'setMinDistance', 'getMinDistance', 'setBlockSize', 'getBlockSize', 'setHarrisDetector', 'getHarrisDetector', 'setK', 'getK', 'getDefaultName'],
              # 'SimpleBlobDetector': ['create'],
              'KAZE': ['create', 'setExtended', 'getExtended', 'setUpright', 'getUpright', 'setThreshold', 'getThreshold', 'setNOctaves', 'getNOctaves', 'setNOctaveLayers', 'getNOctaveLayers', 'setDiffusivity', 'getDiffusivity', 'getDefaultName'],
              'AKAZE': ['create', 'setDescriptorType', 'getDescriptorType', 'setDescriptorSize', 'getDescriptorSize', 'setDescriptorChannels', 'getDescriptorChannels', 'setThreshold', 'getThreshold', 'setNOctaves', 'getNOctaves', 'setNOctaveLayers', 'getNOctaveLayers', 'setDiffusivity', 'getDiffusivity', 'getDefaultName'],
              'DescriptorMatcher': ['add', 'clear', 'empty', 'isMaskSupported', 'train', 'match', 'knnMatch', 'radiusMatch', 'clone', 'create'],
              'BFMatcher': ['isMaskSupported', 'create'],
              '': ['drawKeypoints', 'drawMatches', 'drawMatchesKnn']}

photo = {'': ['createAlignMTB', 'createCalibrateDebevec', 'createCalibrateRobertson', \
              'createMergeDebevec', 'createMergeMertens', 'createMergeRobertson', \
              'createTonemapDrago', 'createTonemapMantiuk', 'createTonemapReinhard', 'inpaint'],
        'CalibrateCRF': ['process'],
        'AlignMTB' : ['calculateShift', 'shiftMat', 'computeBitmaps', 'getMaxBits', 'setMaxBits', \
                      'getExcludeRange', 'setExcludeRange', 'getCut', 'setCut'],
        'CalibrateDebevec' : ['getLambda', 'setLambda', 'getSamples', 'setSamples', 'getRandom', 'setRandom'],
        'CalibrateRobertson' : ['getMaxIter', 'setMaxIter', 'getThreshold', 'setThreshold', 'getRadiance'],
        'MergeExposures' : ['process'],
        'MergeDebevec' : ['process'],
        'MergeMertens' : ['process', 'getContrastWeight', 'setContrastWeight', 'getSaturationWeight', \
                          'setSaturationWeight', 'getExposureWeight', 'setExposureWeight'],
        'MergeRobertson' : ['process'],
        'Tonemap' : ['process' , 'getGamma', 'setGamma'],
        'TonemapDrago' : ['getSaturation', 'setSaturation', 'getBias', 'setBias', \
                          'getSigmaColor', 'setSigmaColor', 'getSigmaSpace','setSigmaSpace'],
        'TonemapMantiuk' : ['getScale', 'setScale', 'getSaturation', 'setSaturation'],
        'TonemapReinhard' : ['getIntensity', 'setIntensity', 'getLightAdaptation', 'setLightAdaptation', \
                             'getColorAdaptation', 'setColorAdaptation']
        }

aruco = {'': ['detectMarkers', 'drawDetectedMarkers', 'drawAxis', 'estimatePoseSingleMarkers', 'estimatePoseBoard', 'estimatePoseCharucoBoard', 'interpolateCornersCharuco', 'drawDetectedCornersCharuco'],
        'aruco_Dictionary': ['get', 'drawMarker'],
        'aruco_Board': ['create'],
        'aruco_GridBoard': ['create', 'draw'],
        'aruco_CharucoBoard': ['create', 'draw'],
        'aruco_DetectorParameters': ['create']
        }

calib3d = {'': ['findHomography', 'calibrateCameraExtended', 'drawFrameAxes', 'estimateAffine2D', \
                'getDefaultNewCameraMatrix', 'initUndistortRectifyMap', 'Rodrigues', \
                'solvePnP', 'solvePnPRansac', 'solvePnPRefineLM']}


white_list = makeWhiteList([core, imgproc, objdetect, video, dnn, features2d, photo, aruco, calib3d])

Answer 1

我遇到了同样的问题。我使用 emscripten 从源代码编译 opencv，它没有任何错误地完成，但是当我试图在浏览器中加载它时，它根本不起作用。问题已通过旧版本的 emscripten 解决。

git clone https://github.com/emscripten-core/emsdk.git
cd emsdk/
./emsdk install 1.39.15
./emsdk activate 1.39.15
source ./emsdk_env.sh
git clone https://github.com/opencv/opencv.git
emcmake python ./opencv/platforms/js/build_js.py build_wasm --build_wasm

我浏览了所有较新的版本，但 1.39.15 是对我有用的最新版本。通过这种方式，我将 opencv.js 文件减小到 1.7MB。