I am trying to implement a simple feature (any language is fine) to recognize and fit perfect shapes (rectangle, triangle, circle, etc.) from hand-drawn sketched shapes. There are many existing tools support that, for example, Procreate's QuickShape, Apple Notes App which can automatically convert your drawing into a perfect shape, etc. Other works recognize the shape categories easily, like the $1 recognizer, but cannot provide a fit perfect shape but only the category. I believe this is a well-researched topic and there must be a library or algorithm that could do that, given any sequence of touch locations [(x,y)]. Can anyone help me find that or tell me where to start? Thanks!
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I hope that this is the correct place to ask this kind of question. I am developing a web app to design garden ponds and I need to calculate the shape and size of the foil needed to cover that pond. The pond will provided as a 3D model (threeJS). The shape of the pond will be relatively simple (think one or more rectangular boxes potentially with some stairs).
I am considering folding out the surface of the 3D model into a flat shape, but I do not know how to do that in a generic way. And even if a could od that it would not be the complete solution (but potentially it would be a starting point) I have been searching for a generic algorithm to do this, but so far have not found anything. Does anyone know of an algorithm that I could use for this, or at least something that I could start with.
Some additonal information:
this will be a browser based solution which should show the pool; one option would be ThreeJS since I am somewhat familiar with it
the foil that should cover the pond needs to watertight, so it needs to be one piece. That means that when your put it in the pool, it form rinkle, especially in the corners.
I have an idea for an app that takes a printed page with four squares in each corner and allows you to measure objects on the paper given at least two squares are visible. I want to be able to have a user take a picture from less than perfect angles and still have the objects be measured accurately.
I'm unable to figure out exactly how to find information on this subject due to my lack of knowledge in the area. I've been able to find examples of opencv code that does some interesting transforms and the like but I've yet to figure out what I'm asking in simpler terms.
Does anyone know of papers or mathematical concepts I can lookup to get further into this project?
I'm not quite sure how or who to ask other than people on this forum, sorry for the somewhat vague question.
What you describe is very reminiscent of augmented reality marker tracking. Maybe you can start by searching these words on a search engine of your choice.
A single marker, if done correctly, can be used to identify it without confusing it with other markers AND to determine how the surface is placed in 3D space in front of the camera.
But that's all very difficult and advanced stuff, I'd greatly advise to NOT try and implement something like this, it would take years of research... The only way you have is to use a ready-made open source library that outputs the data you need for your app.
It may even not exist. In that case you'll have to buy one. Given the niché of your problem that would be perfectly plausible.
Here I give you only the programming aspect and if you want you can find out about the mathematical aspect from those examples. Most of the functions you need can be done using OpenCV. Here are some examples in python:
To detect the printed paper, you can use cv2.findContours function. The most outer contour is possibly the paper, but you need to test on actual images. https://docs.opencv.org/3.1.0/d4/d73/tutorial_py_contours_begin.html
In case of sloping (not in perfect angle), you can find the angle by cv2.minAreaRect which return the angle of the contour you found above. https://docs.opencv.org/3.1.0/dd/d49/tutorial_py_contour_features.html (part 7b).
If you want to rotate the paper, use cv2.warpAffine. https://docs.opencv.org/3.0-beta/doc/py_tutorials/py_imgproc/py_geometric_transformations/py_geometric_transformations.html
To detect the object in the paper, there are some methods. The easiest way is using the contours above. If the objects are in certain colors, you can detect it by using color filter. https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_imgproc/py_colorspaces/py_colorspaces.html
I'm looking to implement a simple morphing animation between two images.
Here's a simple demo of what I'm trying to create: http://i.imgur.com/7377yHr.gif
I'm pretty comfortable with Objective-C and JavaScript but since the concepts and algorithms are abstract, I'm more than willing to see examples in any language or framework.
I would like to know how hard it would be to tackle this -- it doesn't have to be exact but as long as it gives the impression of a morph I'll be satisfied.
Where would I start?
It seems like in your example is being used a combination of mesh wrap morphing and cross dissolve morphing. Mesh morphing can be tricky and as far as I know it requires a manual input (defining the mesh), so depending on what you want to do it might not be suitable for you.
If you are looking for a cheap technique (in terms of effort), probably just doing cross dissolve would work for you, since is very easy to implement. You just need to combine both images by increasing the alpha of the target image and decreasing the alpha on the origin image.
These articles give an overview of the techniques:
[PDF] http://css1a0.engr.ccny.cuny.edu/~wolberg/pub/vc98.pdf
[PDF] http://www.sorging.ro/en/member/serveFile/format/pdf/slug/image-morphing-techniques
[PDF] http://cs.haifa.ac.il/hagit/courses/ip/Lectures/Ip05_GeomOper.pdf
The last link comes from a comment in a similar question: Morphing, 3 algorithms, image processing
Given a set of 2d images that cover all dimensions of an object (e.g. a car and its roof/sides/front/read), how could I transform this into a 3d objdct?
Is there any libraries that could do this?
Thanks
These "2D images" are usually called "textures". You probably want a 3D library which allows you to specify a 3D model with bitmap textures. The library would depend on platform you are using, but start with looking at OpenGL!
OpenGL for PHP
OpenGL for Java
... etc.
I've heard of the program "Poser" doing this using heuristics for human forms, but otherwise I don't believe this is actually theoretically possible. You are asking to construct volumetric data from flat data (inferring the third dimension.)
I think you'd have to make a ton of assumptions about your geometry, and even then, you'd only really have a shell of the object. If you did this well, you'd have a contiguous surface representing the boundary of the object - not a volumetric object itself.
What you can do, like Tomas suggested, is slap these 2d images onto something. However, you still will need to construct a triangle mesh surface, and actually do all the modeling, for this to present a 3D surface.
I hope this helps.
What there is currently that can do anything close to what you are asking for automagically is extremely proprietary. No libraries, but there are some products.
This core issue is matching corresponding points in the images and being able to say, this spot in image A is this spot in image B, and they both match this spot in image C, etc.
There are three ways to go about this, manually matching (you have the photos and have to use your own brain to find the corresponding points), coded targets, and texture matching.
PhotoModeller, www.photomodeller.com, $1,145.00US, supports manual matching and coded targets. You print out a bunch of images, attach them to your object, shoot your photos, and the software finds the targets in each picture and creates a 3D object based on those points.
PhotoModeller Scanner, $2,595.00US, adds texture matching. Tiny bits of the the images are compared to see if they represent the same source area.
Both PhotoModeller products depend on shooting the images with a calibrated camera where you use a consistent focal length for every shot and you got through a calibration process to map the lens distortion of the camera.
If you can do manual matching, the Match Photo feature of Google SketchUp may do the job, and SketchUp is free. If you can shoot new photos, you can add your own targets like colored sticker dots to the object to help you generate contours.
If your images are drawings, like profile, plan view, etc. PhotoModeller will not help you, but SketchUp may be just the tool you need. You will have to build up each part manually because you will have to supply the intelligence to recognize which lines and points correspond from drawing to drawing.
I hope this helps.
I'm sorry if my question is somewhat vague. It's been a few years since I did anything with Qt, and back then I never did any fancy image stuff. What I'm asking for below is just some general suggestions on which classes to consider using. I'm trying to avoid barking up the wrong tree from the very start.
The situation: I'm writing a Qt-based program in which I need to display a somewhat large (let's say 5000x5000) raster image. The user should be able to zoom (quickly) in and out, and pan around the image in a way similar to for example Google maps. So far, this is not very different from the Qt ImageViewer example, except perhaps for the requirement that zooming happens quickly. However, I need to draw on the order of 50k simple geometric shapes (let's say circles) on top of the image, and be able to add and remove some of these in a simple way. The circles should have the same size no matter the zoom level, and should thus either be redrawn whenever the user zooms, or should be drawn with vector graphics. Think of the circles as map annotations. These should look the same at any zoom level, and also behave nicely with respect to panning.
I guess my question is twofold:
Can Qt draw vector graphics on top of a raster image?
In general, which classes should I consider for the above?
Thanks in advance. I don't like answering vague questions myself, but maybe someone with experience with Qt's graphics capabilities has an answer.
I suggest you use QGraphicsView and friends for this. It helps handling all the view/world transformation and the vector items can be achieved with various QGraphicsItems.
You can change the sizes of the items whenever the zoom level changes to maintain constant apparent sizes.