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POConvert OpenCV-Python to C++/Objective C
 

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  1. POConvert OpenCV-Python to C++/Objective C
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    <p>I found this very nice code from @abid-rahman-k to detect a rectangle from image: <a href="https://stackoverflow.com/questions/10533233/opencv-c-obj-c-advanced-square-detection">OpenCV C++/Obj-C: Advanced square detection</a> Now the code is in Python and here it is:</p> <pre><code>import cv2 import numpy as np img = cv2.imread('sof.jpg') img = cv2.resize(img,(500,500)) gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) ret,thresh = cv2.threshold(gray,127,255,0) contours,hier = cv2.findContours(thresh,cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE) for cnt in contours: if cv2.contourArea(cnt)&gt;5000: # remove small areas like noise etc hull = cv2.convexHull(cnt) # find the convex hull of contour hull = cv2.approxPolyDP(hull,0.1*cv2.arcLength(hull,True),True) if len(hull)==4: cv2.drawContours(img,[hull],0,(0,255,0),2) cv2.imshow('img',img) cv2.waitKey(0) cv2.destroyAllWindows() </code></pre> <p>I would like to convert it into Objective C/ C++. This is what I did, but did not work, what did I miss?</p> <pre><code>- (void)processImage2:(cv::Mat&amp;)image; { cv::Mat img,gray,thresh; std::vector&lt;std::vector&lt;cv::Point&gt; &gt; contours; // cv::resize(image.clone(), image, cv::Size(500,500) ); cvtColor(image, gray, cv::COLOR_BGR2GRAY ); cv::threshold(gray, thresh, 127, 255, 0); findContours(thresh, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE); std::vector&lt;cv::Point&gt; hull; for (size_t i = 0; i &lt; contours.size(); i++) { if (cv::contourArea(contours[i])&gt;5000){ cv::convexHull(contours[i],hull); approxPolyDP(hull, hull, 0.1*arcLength(hull, true), true); if (hull.size() ==4) cv::drawContours(image,hull,0,cv::Scalar(0,255,0),2); } } } </code></pre> <p>Update:</p> <p>The program runs but after I select the image it crashes and I get this error:</p> <pre><code>Nov 28 10:26:52 Anas-Basalamahs-MacBook-Air.local OpenCV Tutorial[18861] &lt;Error&gt;: CGBitmapContextCreate: unsupported parameter combination: 0 integer bits/component; 0 bits/pixel; 0-component color space; kCGImageAlphaNone; 0 bytes/row. Nov 28 10:26:52 Anas-Basalamahs-MacBook-Air.local OpenCV Tutorial[18861] &lt;Error&gt;: CGContextConcatCTM: invalid context 0x0 Nov 28 10:26:52 Anas-Basalamahs-MacBook-Air.local OpenCV Tutorial[18861] &lt;Error&gt;: CGContextSetInterpolationQuality: invalid context 0x0 Nov 28 10:26:52 Anas-Basalamahs-MacBook-Air.local OpenCV Tutorial[18861] &lt;Error&gt;: CGContextDrawImage: invalid context 0x0 Nov 28 10:26:52 Anas-Basalamahs-MacBook-Air.local OpenCV Tutorial[18861] &lt;Error&gt;: CGBitmapContextCreateImage: invalid context 0x0 2012-11-28 10:26:52.963 OpenCV Tutorial[18861:c07] resized image size: NSSize: {0, 0} OpenCV Error: Assertion failed (i &lt; 0) in getMat, file /Users/bloodaxe/Develop/opencv/modules/core/src/matrix.cpp, line 957 terminate called throwing an exception(lldb) </code></pre>
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    1. COwhat do you mean it didn't work? Is result wrong? then upload the result you got. Does your code show any error? then update your answer with error log.
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    2. CO@AbidRahmanK check my update
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