How to select a bounding box ( ROI ) in OpenCV (C++/Python) ?
Game Development Stack Exchange is a question and answer site for professional and independent game developers. It only takes a minute to sign up. Assume that each Box object has the properties x, y, width, height and have their origin at their center, and that neither the objects nor the bounding boxes rotate. In English: On each axis, check to see if the centers of the boxes are close enough that they'll intersect.
If they intersect on both axes, then the boxes intersect. If they don't, then they don't. DoBoxesIntersect a, b. It's worth mentioning that you can get a small but significant speed increase by storing the half-width and half-height in addition to or instead of the full width and full height.
On the other hand, it's rare for 2d bounding box intersection to be the performance bottleneck.
This works for two rectangles aligned with the X and Y axis. Each rectangle has the properties: "left", the x coordinate of its left side, "top", the y coordinate of its top side, "right", the x coordinate of its right side, "bottom", the y coordinate of its bottom side.
The idea is to capture all possible conditions upon which the rectangles will not overlap, and then negate the answer to see if they are overlapped. Regardless of the direction of the axes, it's easy to see that two rectangles will not overlap if:. SAT isn't the fastest solution, but it's relatively simple. You're trying to find a single line or a plane if 3D that will seperate your objects.
If this line exists it's guarenteed to be paralell to the edge of one of your boxes, so you iterate through all edges testing to see if it seperates the boxes. Lot of math here for a very simple problem, assume that we have 4 points determined for a rect, top, left, bottom, right The DoBoxesIntersect above is a good pairwise solution.
In the 3D collision detection literature, this is known as having both a broad-phase and a narrow-phase algorithm. We'll do something really fast to find all possible pairs of overlaps, and then something more expensive to see if our possible pairs are actual pairs.
The broad-phase algorithm I've used before is "sweep-and-prune"; for 2D, you'd maintain two sorted lists of the start and end of each box. Depending on the problem you try to solve you might be better off keeping track of your object while you move them, ie, keep a list of sorted x start and end positions and one for start and end y positions. If you have to do a LOT of overlap checks and therefore need to optimize, you can use this to your advantage, as you can immediately look up who is ending closes to your left, everyone who's ending is to the left of that can be pruned immediately.If you've got a moment, please tell us what we did right so we can do more of it.
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The bounding box around the detected page, text, key-value pair, table, table cell, or selection element on a document page. The left x-coordinate and top y-coordinate are coordinates that represent the top and left sides of the bounding box.
Note that the upper-left corner of the image is the origin 0,0. The top and left values returned are ratios of the overall document page size. For example, if the input image is x pixels, and the top-left coordinate of the bounding box is x 50 pixels, the API returns a left value of 0. The width and height values represent the dimensions of the bounding box as a ratio of the overall document page dimension.
For example, if the document page size is x pixels, and the bounding box width is 70 pixels, the width returned is 0. The height of the bounding box as a ratio of the overall document page height. The left coordinate of the bounding box as a ratio of overall document page width. The top coordinate of the bounding box as a ratio of overall document page height. The width of the bounding box as a ratio of the overall document page width.Create own Dataset - Boundary BOX - Image annotation - xml_to_csv
Contents See Also. Did this page help you? Thanks for letting us know we're doing a good job! Height The height of the bounding box as a ratio of the overall document page height. Type: Float Required: No Left The left coordinate of the bounding box as a ratio of overall document page width.
Type: Float Required: No Top The top coordinate of the bounding box as a ratio of overall document page height. Type: Float Required: No Width The width of the bounding box as a ratio of the overall document page width.
Type: Float Required: No. Document Conventions.Most popular metrics used to evaluate object detection algorithms. Is your feature request related to a problem? Please describe. Having a shortcut to move around the images would be a big usability improvement given that the toolbar moves depending on the image resolution.
Also it speed ups annotations. Fast algorithms to compute an approximation of the minimal volume oriented bounding box of a point cloud in 3D. This is a repository for an object detection inference API using the Tensorflow framework.
Currently the output class ID is dependent on the order in which they were created in deeplabel. Tensorflow object detection with tracking based on the DeepSort algorithm. Image augmentation with simultaneous transformation of keypoints, bounding boxes, and segmentation mask. Pixie is a GUI annotation tool which provides the bounding box, polygon, free drawing and semantic segmentation object labelling.
Script to download frames only from the YouTube Bounding Boxes dataset. Lane and obstacle detection for active assistance during driving. Uses windowed sweep for lane detection. Combination of object tracking and YOLO for obstacles. Determines lane change, relative velocity and time to collision.
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Polygon Objects. Enter search terms or a module, class or function name. Bounding boxes are axis-aligned rectangles. They are the simplest closed shape type in planarrepresented by two points containing the minimum and maximum coordinates for each axis.
Bounding boxes can be useful as standalone shapes, but they are primarily used for approximating more complex shapes to speed operations such as containment checks and intersection.
Bounding boxes can also be constructed directly from an arbitrary sequence of points. This creates the smallest BoundingBox object that encloses all of these points:. The bounding box of a bounding box is just itself, which may seem silly, but it lets you include BoundingBox instances in collections of other shapes without special casing them. For example, you can construct a BoundingBox object from a sequence of shapes.
The resulting bounding box encloses all of the shapes provided:. It is also possible to create a BoundingBox from a center point, specifying its width and height explicitly:. This is the corner with the smallest x and y value.
This is the corner with the largest x and y value. This is done automatically by built-in planar shapes where appropriate, but you can employ this strategy yourself if you create your own custom shape classes with planar primitives. If you have multiple non-overlapping shapes that share edges, the method will return True for, at most, one shape for any given test point. Because bounding boxes are often derived from other shapes and also cachedthey are themselves immutable.
Thus, you cannot directly modify the attributes of a BoundingBoxand operations that would modify the shape will return a new instance. As with all shapes, transforms can be applied to bounding boxes by multiplying. The type of the resulting shape depends on the transform. Rectilinear transforms that preserve axis-alignment will result in a new BoundingBox instance when transformed. Such transforms include translation, scale, and rotation by multiples of 90 degrees:.
Non-rectilinear transforms can be applied to BoundingBox objects as well, but the result will be a Polygon since the resulting shape will no longer be axis-aligned:. Bounding boxes can also be converted directly to an equivalent 4-sided Polygon. Since polygons are mutable, this is one way to get around the immutability of BoundingBox instances.
This can also be useful to easily convert a bounding box into a sequence of 4 points, which may be more convenient to draw:. You can shrink and expand a bounding box about its center point by an absolute amount using the inflate method. This method allows you to derive a new bounding box that is wider or higher than an existing one by fixed values. You can provide a single number to inflate to change the width and height by the same absolute amount. Positive amounts increase the size while negative amounts decrease it.
You can alter the width and height independently by providing a sequence of two numbers, such as a tuple, or Vec2 object:. The BoundingBox fit method takes an input shape and creates a transformed version that is translated and scaled so that it fits in the bounding box. The input shape is scaled evenly to preserve its aspect ratio. Navigation index modules next previous Planar v0. Created using Sphinx 1.In this tutorial, we will learn how to select a bounding box or a rectangular region of interest ROI in an image in OpenCV.
In the past, we had to write our own bounding box selector by handling mouse events. I am always amazed by the weird choices made in the OpenCV library.
You would think that selectROI would be part of highgui that has functions for displaying images, drawing on images etc. As you will notice later in the post, the choices made while writing selectROI are a bit odd. But, before we criticize we gotta be thankful that someone produced something useful even though it is not perfect. It allows you to select a rectangle in an image, crop the rectangular region and finally display the cropped image. If you are like me, you would prefer to drag a rectangle from the top left corner to the bottom right corner instead of the dragging it from the center.
Well, we can easily fix that by replacing the highlighted line with the following line. Well here you go. Now, suppose you do not like the crosshair and would like to see the rectangle without it.
You can modify the code to not show the crosshair. The function selectROI also allows you to select multiple regions of interest, but there appear to be two bugs. However, there appears to be a bug in the implementation in OpenCV 3. Bug Alert 2 : I could not get the python version to work and there is no documentation. The following code runs, but the variable rects is not populated.
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 have an image that contains more than one bounding box. I need to extract everything that has bounding boxes in them.
So far, from this site I've gotten this answer:. It works, however, it only gets one. How should I modify the code? I tried putting it in the loop for contours but it still spews out one image instead of multiple ones.
A simple approach is to find all contours, obtain the bounding rectangle coordinates using cv2. We can keep a counter to save each ROI then save it with cv2. Here's a working example:. Learn more. Asked 6 years, 3 months ago.
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Featured on Meta.Just to see if it worked otherwise, I commented it out, and it runs but nothing shows up i. I can press esc and exit, though. Even i got the same error. Just erase line number 46 to 51 and replace it with cv2. How could i make this work when i use a program that retrieves multiple images from google and can pass them through the process?
I get the following error when using the provided hammer. I tried the above code for zebra line detection in an image. It shows output like this. By I need to detect the entire block of zebra crossing. Skip to content. Instantly share code, notes, and snippets.
Code Revisions 6 Stars 22 Forks 1. Embed What would you like to do? Embed Embed this gist in your website. Share Copy sharable link for this gist. Learn more about clone URLs. Download ZIP. This comment has been minimized.
Sign in to view. Copy link Quote reply. Very clean to read code. It doesn't work right out of the box for me. I did download the file beforehand, but python I'm using 3.
Something curious: print len contours prints 0 That's all I've investigated so far. Clean code! I am having an issue with line Has anyone resolved this? Sign up for free to join this conversation on GitHub.
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