Python opencv fill contour. for example, this rectangle center is hole. So what does RETR_FLOODFILL do and how do I use it correctly? For example hierarchy[0][5] has values [ 7 3 6 2] and corresponds to contours[5]. Contours : Getting Started Learn to find and draw Contours Contour Features Learn to find different features of contours like area, perimeter, bounding rectangle etc. This is a simple snippet, I generate a contour of four points representing vertices of a square, then I fill the polygon with a white color. This project captures live video from your webcam, detects a hand inside a defined Region of Interest (ROI), analyzes convexity defects, and estimates the number of fingers extended. imread(img_path) original = image. drawContours function in OpenCV is super useful for drawing outlines of shapes or objects found in an image. Its first argument is source and destination image, second argument is the contours which should be passed as a Python list, third argument is index of contours (useful when drawing individual contour. I would like to gap fill the lines in this image). In this article, I will show how to connect a USB spectrometer using Python and how to process and visualize the data with OpenCV and Matplotlib. Bear in mind that even if you draw the contours with the simple approximation, it will be visualized as having a blue contour drawn completely around the rectangle as seen in the left image. deepcopy (img_copy), cv2. Think of it like a digital pen that traces around areas of interest Learn about OpenCV Functions like cv2. The method is similar to imfill in MATLAB. zeros((image_original. Contours Hierarchy Hello, I have a question concerning the drawContours function. findContours () function, first one is source image, second is contour retrieval mode, third is contour approximation method. Apr 15, 2024 · In this article, we looked at a simple and quick way to contour an image using Python’s most popular computer vision library, OpenCV. findContours (). getTextSize & cv2. I have an image with a black background and some red outlines of polygons, like this: I want now to fill those polygons with the same colour, so they look something like this: I tried using OpenC Contours are edges or outline of a objects in a image and is used in image processing to identify shapes, detect objects or measure their size. ellipse2Poly. shape[0], After sending a converted image to the function, I got 180k contours, resulting the black mess below, if I plot them. fillPoly, cv2. RETR_TREE, cv2. The code below selects the contour and hull along the edges of the hand X-ray: img_path = 'sample_image. It is an implementation of Douglas-Peucker algorithm. And it outputs a modified image, the contours and hierarchy. I noticed that during those iterations my objects get bigger and bigger, and I think it happens when I draw the contours. shape[:2], dtype = np. To draw all contours, pass -1) and remaining arguments are color, thickness etc. How to fill small gaps in a contour in opencv Asked 2 years, 10 months ago Modified 2 years, 10 months ago Viewed 587 times The function draws contour outlines in the image if \ (\texttt {thickness} \ge 0\) or fills the area bounded by the contours if \ (\texttt {thickness}<0\) . See full list on docs. These contours represented boundaries between regions of Prev Tutorial: Template Matching Next Tutorial: Convex Hull Goal In this tutorial you will learn how to: Use the OpenCV function cv::findContours Use the OpenCV function cv::drawContours Theory Code C++ Python 使用OpenCV填充轮廓 在本文中，我们将介绍如何使用Python和OpenCV库来填充轮廓。轮廓是图像处理中常用的概念，通常表示为一系列相连的曲线。轮廓可以用于对象识别、形状分析以及边缘检测等应用中。通过填充轮廓，我们可以给图像中的对象或区域添加颜色或纹理，以便更好地观察和分析 This entry was posted in Image Processing and tagged contours opencv, digital image processing, find and draw contours opencv python, opencv python on 19 Nov 2019 by kang & atul. Except as noted, function signatures and return values are the same for both versions. In the below example we find the contours present in an image files. See, there are three arguments in cv. I managed to get the outline of a map and now I want to paint each of the states with a color, how can I have this python code that supposedly fills the contours of an image, but leaves the holes contained in it unfilled. What I'm looking for is when I have a square contour, fill the inside of this contour using a specific color. findContour I'm trying to separate the contours of an image (in order to find uniform regions) so I applied cvCanny and then cvFindContours, then I use the following code to draw 1 contour each time I press a I have the following image: and I would like to fill in its contours (i. drawContours function in OpenCV. polylines, cv2. In a program of mine, some contours are detected in a binary image, then edited via a some manual brush tool, and then updated with another detect contour run. The original library was written in C++ by Intel, but it also usable through Python bindings. Here is one way to do that in Python/OpenCV. To draw all the contours in an image: 4. Learners will be able to implement real-time hand gesture recognition systems, apply OpenCV-based image processing Enroll for free. We use OpenCV's findContours () function that works best for binary images. png' # Getting the threshold of the image: image = cv2. This tutorial will guide us through image and video processing from the basics to advanced topics using Python and OpenCV. The cv2. I've got this kind of starting image: I'm trying to identify all features in my ima 4 I'm trying to do a mask in cell image just with the ROI, so I applied the contours with OpenCV around the ROI but I've been struggling to get the region inside the contours. We'll learn how to handle image transformations, feature extraction, object Jul 14, 2025 · It continues isophotes (lines joining points with same intensity, just like contours joins points with same elevation) while matching gradient vectors at the boundary of the Hi, I’m trying to find a way to paint an outer contour without painting all the inner contours. I'm trying to display a filled contour using the cv2. What I am trying to do is basically the same as erode/dilate, but instead of an image, I have contours. The example below shows how to retrieve connected components from the binary image and label them: : I am trying to blacken the outside regions of Contours using OpenCV in Python. imread(original_image_path) image_contours = np. Jul 12, 2025 · OpenCV (Open Source Computer Vision Library) is an open-source computer vision and machine learning library. zeros(image. This function is essential for drawing contours on images, which is a common task in image processing and computer vision. In the image above, I want to eventually be able to fill in the contours of the colored circles. For example collecting the indexes of contours where hierarchy[0][0] == -1 or hierarchy[0][3] == 2. Here is my code : contours, hierarchy = cv2. (white each pixel value = 255, black value = 0) but, I want to fill this hole. findContours (copy. I have tried a morphological closing, but using a rectangular kernel o Contours are a powerful tool in OpenCV for shape analysis and object detection. So far when I draw the contour, the border is red and the inside is filled with white : cv::drawContours (targetMat, contours, maxAreaIdx, cv How to enclose the irregular figure contour and fill it with with 5px dots in opencv using python? Asked 5 years, 3 months ago Modified 5 years, 3 months ago Viewed 2k times I am trying to fill a contour which was obtained by separately thresholding 3 color channels. (cv2. (like picture below) how to fill hole by rectangle using OpenCV. I have no idea that how to convert my points to contour representation. Let’s get into it! OpenCV is a library of programming functions mainly aimed at real-time computer vision. fillPoly on the original image. I would like to get an image mask from the contour (it exists only 1 contour) I have computed thanks to cv. Contours help us identify the shapes present in an image. Contour Properties Learn to find different properties of contours like Solidity, Mean Intensity etc. Unfortunately, the yellow circle on the bottom is right at the edge of the image, so cv2. To draw all the contours in an image: For the purpose of image analysis we use the Opencv (Open Source Computer Vision Library) python library. Learn how to use Python OpenCV cv2. By understanding how to find, analyze, and manipulate contours, you can build a wide range of computer vision applications, from simple shape detection to complex document scanners and object tracking systems. These contours represented boundaries between regions of varying intensity. Check the wikipedia page for algorithm and demonstration. It allows us to process images and videos, detect objects, faces and even handwriting. I've searched on the internet and on the openCV forum but without any success. How to fill a contour plot mask and retain data inside the contour and blackout the rest Asked 5 years, 7 months ago Modified 3 years, 5 months ago Viewed 6k times 23 First off, that example only shows you how to draw contours with the simple approximation. I have tried a morphological closing, but using a rectangular kernel of size 3x3 with 10 iterations does not fill in the entire border. org Jan 21, 2026 · In this blog post, I’ll show you how to use Python and OpenCV to fill a circle, rectangle, or any random shape in an image. fillConvexPoly, cv2. e. image_original = cv2. This tutorial describes a method for filling holes in a binary image in OpenCV ( C++ / Python ). Then I found all white pixels in the picture and used these coordinates to apply cv2. The problem is that drawcontours draws all the contours good, BUT it doesnt "fill" the contours that are in the border of the image (this is, the ones that have one boundary in the edge of the image). To the same contour representation w I am trying to color in black the outside region of a contours using openCV and python language. But cannot find a way to fill those two specific areas up. Step-by-step guide with examples and code. copy() blank = np. img I want to know how to paint inside a contour generated with the python function: findContours. You may wonder why we require this type of operation! Jan 15, 2025 · In this guide, we will explore how to use the cv2. findContours () for contour detection in images. How to fill specific areas with white color in opencv-python? I'm trying to make a mask with the contours found in cv2. fillPoly () function to fill the contours with a specified color. I've developed a list of contours from an edge image derived from a Canny detection, and am finding the contours contour and contourf draw contour lines and filled contours, respectively. However, while my contour variable is not empty, I do not manage to retrie Its first argument is source image, second argument is the contours which should be passed as a Python list, third argument is index of contours (useful when drawing individual contour. The library name that has to be imported after installing opencv is cv2. I want to draw it using opencv as contour. I have an image that has green borders which encapsulates the items that has to be deleted. You can use the cv2. Now I need to figure out how to invert and fill everything aro I have the following image: and I would like to fill in its contours (i. Oct 7, 2013 · 67 I think what you are looking for is cv2. I'm trying to identify contours using a Canny filter in openCV and fill the contours, in order to create a mask. How to fill openCV contours with a color specified by its area in Python? Asked 5 years, 6 months ago Modified 4 years, 11 months ago Viewed 3k times I have a set of boundary points of an object. opencv. Contours are defined as the line joining all the points along the boundary of an image In this article, we looked at a simple and quick way to contour an image using Python’s most popular computer vision library, OpenCV. Offered by EDUCBA. findContours. I have filtered the only green part of the image so my next step is to fill inside of the filtered contour This code is helpfull but if we have a big table shape with several rows and cols in image ,as you know table is a big contour and this code make all of table filled and contents of table is unreachable. Contours : More Functions Learn to find convexity defects, pointPolygonTest, match different shapes etc. This happens with all three functions I have tried . Contours Hierarchy I'm trying to find the contours of an image and overlay them (with some transparency) over another image. That way, I am trying to fill in hole-like indents in the contours. This is what I want: But this is what I get: I've tried specifying the contour 4 Always best if you provide separate images. fillPoly, which fills the area bounded by one or more polygons. uint8) I'm trying to get an algorithm that fills the contours of an image with alternating colors: first white, then black, then white again, then black again like how the following picture shows: Wha How do i fill the background outside the contour with white color ? I can get a very good contour around my product(see image bellow). Discover moving object detection using OpenCV, blending contour detection with background subtraction for real-time application in security and traffic. Google Colab Sign in See, there are three arguments in cv. Contour Approximation It approximates a contour shape to another shape with less number of vertices depending upon the precision we specify. However, when I execute the following code I get an undesired effect (see image below). (see the image below - co I actually created a black image (image2) and filled it with the blue contours calculated in white. arrowedLine, cv2. I want to have this region inside white and then discard the contours and the rest outside. For instance, circles increase 1 pixel in diameter every time. Here's a step-by-step example: Hand Gesture Recognition using OpenCV A real-time hand gesture recognition system built with Python and OpenCV. Hope this gives you a basic understanding on how to pick the proper contour for building the final result. contours is a Python list of all the contours in the image. drawContours () function in Python OpenCV. Read the image as grayscale Threshold Apply morphology close Get the one external contour Get the bounding box coordinates of the contour Draw the one white contour as filled on a black background Crop the result Save the results Input: Copy Filling contours in OpenCV in Python can be achieved by drawing filled polygons based on the detected contours. y44uqg, me5e, sid3h, eozu, wlyo, zctw, 6wy68c, pavc8n, 7kwfpe, vygc,