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I am looking for advice on algorithms that would allow me to recognise an image patch of a hand. So given an image, I would like to extract patches that would belong to a hand (those will be positive patches). Everything else would be negative patches.
My target application is to distinguish a hand (of any hand shape) from other objects without using colour, by being able to identify if a patch belongs to a hand..
The figure below depicts what I have in mind,
The only problem with hands is that it can take any shape form. Are there any suggestions or algorithms to do the above?
Thank you in advance.
This is a very broad research topic, so you are unlikely to find any good example software available, but you are likely to find many research papers in this area, and if you are lucky then you might find some where the authors publish their code.
You've given a picture of a cat, so taking that as inspiration I did a quick search and found this paper from the Andrew Zisserman group at Oxford University. Another group to look into is that of Jitendra Malik at University of California at Berkeley who have an interest in this area using a combination of image segmentation and feature detection.
Depending on your motives search terms could include: deformable shape models, skin segmentation (although you say you don't want to use colour - why not?), object detection. The possibilities are numerous, and they are all current research topics throughout a number of computer vision communities.
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I am working on one project and in that i want to make teeth white. So for that need to find teeth part.I have tried equalizeHist, adaptiveThreshold, threshold,dilate, erode etc.But not getting exact teeth part.
So can anyone tell me how can i do it.I am using OpenCV c++ library.
In input i have this image
I have found this type of mask
So if i use this mask the image looks unnatural like this,
I see two problems. You find the correct region, but the boundary is imprecise. That's solvable by looking at the gradient of the hue, which will form a clear contour. If you use the HSL color model, the Lightness component will likely have a sharp contrast too.
Secondly, the bigger effect IMO is that you far overdo the whitening. This loses a lot of contrast between teeth. You probably want to just drop the yellow saturation, but don't touch the luminosity.
If you want to be really fancy, determine where the teeth edges are, and you can smooth out the luminosity elsewhere. This removes small stains on teeth.
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I have a quite specific question: I want to draw a matrix of numbers in a greyscale image. The higher the number the brighter the output. Is there a way to do that in a C++ programme without having dependencies to a graphic library like Qt?
I looked through some examples of ImageMagick, but I'm not sure how to implement its functions in C++.
Answer
In case someone stumbles upon this question:
a modified code of the example shown here was a handy and easy solution
It's hard without a library. SFML seems easy to use.
EDIT
Also you have 3 other questions hidden in your question:
1- To save an image you can use sf::image::saveToFile
2- To get brighter number for higher number: You need to normalize your numbers to [MinColorYouWant MaxColorYouWant] (for example: [128,255]). Thus the normalization value corresponding to each number will become the color of the number.
3- SFML uses RGBA images by default. Just set the RGB channels equal to make it look greyscale.
EDIT 2 : I've fixed the example normalization from [128,256] to [128,255].
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In the "slam for dummies" tutorial, laser scanner was used, and two methods of landmark extraction were shown.
But most practical SLAM implementations are based on camera images. In these applications how are landmarks extracted? The Durrant-Whyte paper does not mention it and I could not find an end-to-end demo project that includes landmark extraction.
Usually landmarks are many distinct, salient features like blobs or corners within an image/frame. Salient features in computer vision are an art in itself. There are dozens of different approaches to extract, describe and match such features (you obviously need to recognize them in different frames).
Wikipedia has an overview and here you see a video of a practical SLAM implementation running on a mobile phone (a little bit of advertising for an excellent university:).
In case of images, they uses feature matching algorithms like SURF or ORB. ORB SLAM, one of the most popular open source slam solution uses ORB feature extraction only.
In vision-based applications, firstly features (interest points) are detected. The feature description step detects salient features only such as corners, blobs etc. and it doesn't make sense alone. Feature descriptors identify each feature in the scene. From this moment, you can choose the ones you want as landmark, keeping in mind your SLAM algorithm.
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I have a problem while running my game. The model that I import in the game is quite big, making the fps drop down. That's okay but when I get the camera off from the model, it still stays slow. As other games do, when looking at a high resolution model, the game slows down but when not looking at it, it gets faster. However my game stays slow all the time. Can anyone help me?
You need to implement clipping, so that you don't render the object (i.e. pass it through the graphics pipeline) when it's not visible.
There are many techniques and algorithms/data structures for this, ranging from manual view frustum-testing, to more advanced spatial-querying data structures (BSPs, quadtrees, octrees and so on).
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I want to begin looking at Direct X, but don't just want to try and throw myself into it. What are some good resources to get ones feet wet?
I highly recommend Toymaker's tutorials. Helped me greatly when I was first starting out with DX and was just as good as a reference later on.
The other thing to do would to set up some small projects that use DX that increase in difficulty as you go. If you'd like a starter list (from easy to hard):
Compiling using DX libraries (I always remeber having trouble linking the libraries correctly in Visual Studio).
Change background colour.
See a model on-screen.
Moving the model with input.
A camera.
Apply a texture to your model.
Add multiple models to your scene.
Add lighting.
Create your a simple rectangle model and display a texture on it.
Get comfortable with all that and then have a look at shaders, advanced lighting and animation.
There are quite a few books on directX, but there is so much freely available information on the web these days, I would just jump right in there.
A good place to start is just to do a youtube search for DirectX Tutorials. In my opinion, this is a fun and interesting way to get started learning a new dev skill.