Cv2 mask to polygon

GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. Could you please share the function that converts masks to polygons, which you used to generate the segmentation annotations for COCO dataset?

Because I would like to train the deepMask on my dataset, which needs to represent masks by polygons to generate the groundtruth. I had the same problem and I'm afraid there is no function that works out of the box. First of all, you need to decide whether you are ok with the assumption that the shapes are convex.

If so, you can easily get the convex hull of each object segment, with e.

Extracting polygon given coordinates from an image using OpenCV

Otherwise, you need to get the outline of your shape only points on the perimetere. This is necessary because given a set of points, there are multiple concave hulls you can draw, but only a single convex one. Therefore, you will need to create a list of perimeter points, sorted in either clockwise or counter-clockwise order.

Technically, having these outline points should be enough, as long as they are sorted; the problem is it's a huge set of polygon vertices and will probably be computationally expensive to use as input. You can look here or here for how to sample your points and end up with a proper polygon.

Apparently it's a common GIS task. As far as I know there isn't a more straight-forward way. Maybe you can try this one or this one not sure whether they work, haven't tested them myself. I've written a python library that might help others. Take a look at the docs for more detail.This post will be helpful in learning OpenCV using Python programming. Here I will show how to implement OpenCV functions and apply them in various aspects using some great examples.

Then the output will be visualized along with the comparisons. We will also discuss the basic of image processing and provide the detail explanation related to the OpenCV functions. By following the tutorial you will be able to draw any kind of polygon shapes on images. As a result, you can draw the perfect polygon shape that you want using the opencv python coding. This is an overloaded member function, provided for convenience.

It differs from the above function only in what argument s it accepts. Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. This site uses Akismet to reduce spam. Learn how your comment data is processed.

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cv2 mask to polygon

We are here to help you. Latest posts by Life2Coding see all. Leave a Reply Cancel reply Your email address will not be published. Flag indicating whether the drawn polylines are closed or not.Today, I was in need of a custom ROI a parallellogram. In OpenCV, the way to do this is to use a mask.

The code I used can be seen in the code block below. The mask looks like this:. The subtracted part is shown here:. Welcome to my website! I try to know as much as possible about electronicsrobotics and programming. Every day is a learning experience, and I hope to use this website as a way to organize the chaos in my head.

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cv2 mask to polygon

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The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I want to draw the polygon defined by these points in the image and then extract it. How can I do that using OpenCV with python? Use cv2. Some fair warning should be made where the points that are defined in your polygon are convex hence the name fillConvexPoly.

We can then convert this to a Boolean mask and use this to index into your image to extract out the pixels you want.

The code below produces an array called mask and this will contain a Boolean mask of the pixels you want to save from the image. In addition, the array out will contain the desired extracted subimage that was defined by the polygon. Take note that the image is initialized to be completely dark and that the only pixels that are to be copied over are the pixels defined by the polygon. Assuming the actual image is called imgand assuming that your x and y points denote the horizontal and vertical coordinates in the image, you can do something like this:.

If you want to display this image, you can do something like:.

OpenCV Python Tutorial For Beginners 11- Bitwise Operations (bitwise AND, OR, NOT and XOR)

This will display the extracted image from the polygon points and wait for a key pressed by you. When you are finished looking at the image, you can push any key as long as the display window has focus.

This will save the image to a file called output. I specify the PNG format because it's lossless. As a simple test, let's define a white image that is xwhich is well beyond the largest coordinates in what you have defined.

Let's extract out the region that's defined by that polygon and show what the output looks like. If you would like to translate the extracted image so that it's in the middle, and then place a square around the bounding box, a trick that I can suggest is to use cv2. Once you're done, use cv2. How cv2. Because you're ultimately moving the output to the centre of the image, you need to add an offset to every x and y location in the destination image to get the source pixel.

To figure out the right offsets to move the image, simply figure out the centroid of the polygon, translate the polygon so that centroid is at the origin, and then retranslate it so that it's at the centre of the image. Once you find the centroid, you take all points and subtract by this centroid, then add the appropriate coordinates to retranslate to the centre of the image.

The centre of the image can be found by:. It's also important that you convert the coordinates into integer as the pixel coordinates are such:. Now, translate your image.

You need to define a mapping for each pixel in the output image where for each point x,y in the destination image, you need to provide where to sample from the source. The offset that we calculated translates each source pixel to the destination location.

Because we're doing the oppositewhere for each destination pixel, we are finding which source pixel to sample from, we must subtract the offset, not add. Therefore, first define a grid of x,y points normally, then subtract the offset. Once you're done, translate the image:. Now it's time to draw the rectangle on top of this image.I need some help with cropping cv::Mat. There are a src mat image and a polygon to be cropped for example triangle. Then I filled my mask with 0 value and draw polygon on it using cv::fil lPoly function.

Finally, I try to apply the mask to src image using Mat::copyTo function but nothing happens with src img. What I do wrong? This helped me alot. I do not think that you can have a Mat that is not rectangular, so the best way is to find the minimum bounding rectangle and have just that region. In your code you are displaying some other Mat mFrame which is not altered in the Window.

Asked: Do all opencv functions support in-place mode for their arguments? What is the most effective way to access cv::Mat elements in a loop?

Sobel derivatives in the 45 and degree direction. Saving an image with unset pixels. How to enable vectorization in OpenCV? First time here?

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Check out the FAQ! Hi there! Please sign in help. How to crop non rectangular area from Mat? Hello everybody, I need some help with cropping cv::Mat. Sorry for my bad English. Hi densvr! If you want to mask only a part of one image into another image, you can do that by this method. Mat Destination; Source. Question Tools Follow.

Related questions roipoly matlab function equivalent in OpenCV Do all opencv functions support in-place mode for their arguments? Sobel derivatives in the 45 and degree direction finding centroid of a mask Extract a RotatedRect area Saving an image with unset pixels How to enable vectorization in OpenCV?

Object detection slow Difference of Gaussian Filtering. Copyright OpenCV foundation Powered by Askbot version 0. Please note: OpenCV answers requires javascript to work properly, please enable javascript in your browser, here is how.

Ask Your Question.Tag: pythonopencvimage-processing. I want to draw the polygon defined by these points in the image and then extract it. How can I do that using OpenCV with python? Use cv2. Some fair warning should be made where the points that are defined in your polygon are convex hence the name fillConvexPoly.

We can then convert this to a Boolean mask and use this to index into your image to extract out the pixels you want. The code below produces an array called mask and this will contain a Boolean mask of the pixels you want to save from the image.

In addition, the array out will contain the desired extracted subimage that was defined by the polygon. Take note that the image is initialized to be completely dark and that the only pixels that are to be copied over are the pixels defined by the polygon. Assuming the actual image is called imgand assuming that your x and y points denote the horizontal and vertical coordinates in the image, you can do something like this:.

If you want to display this image, you can do something like:. This will display the extracted image from the polygon points and wait for a key pressed by you. When you are finished looking at the image, you can push any key as long as the display window has focus.

This will save the image to a file called output. I specify the PNG format because it's lossless. As a simple test, let's define a white image that is xwhich is well beyond the largest coordinates in what you have defined. Let's extract out the region that's defined by that polygon and show what the output looks like. If you would like to translate the extracted image so that it's in the middle, and then place a square around the bounding box, a trick that I can suggest is to use cv2.

Once you're done, use cv2. How cv2. Because you're ultimately moving the output to the centre of the image, you need to add an offset to every x and y location in the destination image to get the source pixel.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project?

Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub?

Sign in to your account.

Custom ROI (Region Of Interest) with OpenCV

Recently I tried to add my custom coco data to run Detectron and encountered the following issues. I generated data like this. I found the bolded characters is different from the original coco "segmentation" json format although it can run on MatterPort's implementation to Mask-RCNN.

Also, I tried to modify some Detectron's code to meet my requirement, but very difficult to me because lots of code need to change. For example "" ,a large number! SundropsAs your method to convert, can get the result of "poly" list. SundropsThanks for your great help. My custom coco-like data can be trained on Detectron now. As Sundrops 's method, i can't find the file to convert mask to polys. Could you tell me which file? Thank you very much!

In the code base there is no file of the related annotation. Each label are stored in a single file, so I have N image for label.

cv2 mask to polygon

Could you share the code how to convert it to COCO style? Why not use Davis that contains instance segmenyation? Could we use your code to convert Davis to coco format to use this maskrcnn implementation? Another solution to generating polygons, but using skimage instead of opencv. Are these two results both correct and can these two results both be used by Detectron?

Please give me some advice, thank you. Results with Sundrops code using cv Kongsea I haven't tested Sundrops cv2 implementation, but the basic idea should be the same. They will produce different results since there are an infinite amount of sets of points you can use to describe a shape. But otherwise they should both work. I just didn't have cv2 installed so I wrote something that doesn't require it.


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