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Questions tagged [computer-vision]

Use this tag for questions related to Computer Vision -- any aspect of software that enables computers to perceive, understand and react to their environment using cameras. For questions related to image filtering and quantification, use the tag [image-processing] instead.

Computer vision enables images, or sequences of images, to be processed by a computer using algorithms. There are many aspects to computer vision, including mathematics, physics (especially optics), imaging hardware, , and .

Some basic techniques used in computer vision are:

  • Image acquisition
  • Pre-processing
  • Feature Extraction
  • Detection/Segmentation
  • High-Level processing
  • Decision making
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How to create a single constant-length feature vector from a variable number of image descriptors (SURF)

My problem is as follows: I have 6 types of images, or 6 classes. For example, cat, dog, bird, etc. For every type of image, I have many variations of that image. For example, brown cat, black dog, etc. I'm currently using a Support Vector Machine…
trianta2
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Basics of normalized cross correlation

I am trying to use normxcorr2 (normalized cross-correlation) from MATLAB for calculating velocity of moving shapes in a developing embryo. I have 3 questions: 1) My image size is 260x360 pixels. I give a template size of 10x10 pixels and I ask the…
sundar
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Image size consideration for Haar cascades

The OpenCV Haar cascade classifier seems to use 24x24 images of faces as its positive training data. I have two questions regarding this: What are the consideration that go into selecting the training image size, besides the fact that larger…
angelatlarge
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Why is neural network not predicting?

I am trying to train a neural network using backpropagation algo. in OpenCV 2.3. However it is not predicting correctly....not even on training dataset. Could anybody please help me find whats wrong here? training_feature_matrix - Nx69 matrix of…
learner
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Detecting a Specific Watermark in a Photo with Python (without SciPy)

I have a large number of images (hundreds of thousands) and, for each one, I need to say whether or not it has a watermark in the top right corner. The watermark is always the same and is in the same position. It takes the form of a ribbon with a…
alan
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Strange Octave value in SIFT algorithm?

I am using sift algorithm in opencv code to get descriptors and keypoints from images.My code is Ptr image; vector keypoints; OutputArray des; Feature2D *descriptor_type = new SIFT() Mat image_mat(image); …
zhfkt
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Simple Multi-Blob Detection of a Binary Image?

If there is a given 2d array of an image, where threshold has been done and now is in binary information. Is there any particular way to process this image to that I get multiple blob's coordinates on the image? I can't use openCV because this…
ivanwong888899999
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OpenCV help me with Sepia kernel

I am trying to create a sepia effect. This is the code I am trying: Mat image_copy; cvtColor(image, image_copy, CV_BGRA2BGR); Mat kern = (Mat_(4,4) << 0.272, 0.534, 0.131, 0, 0.349, 0.686, 0.168, 0, …
Richard Knop
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what is the latest and best face recognition algorithm?

am doing my final project that includes face recognition and am trying to implement it on matlab. can anybody help me on getting some resources on each algorithms and their pro's and cons. plus if i get their matlab implementation i would be…
Serak Shiferaw
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Setting parameters for BRISK in OpenCV

I'm trying to use BRISK implementation of OpenCV (for C++) in order to check in a photo if an image (or a part of an image) is included in. For example, I take a photo, and I try to match it with a set of images in database, and I would like to…
user2180398
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Curve reconstruction implementation

Last couple of days I spent on searching for curve reconstruction implementations, and found none - not as a library nor as a tool. To describe my problem. My main concern are contours with gaps: From papers I've read in the meantime, I guess…
theta
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Maze solving by image recognition

I'm trying to do a project with some of my friends, and we came upon that: Say I had to decipher this Labyrinth programmatically, how could I go on about that? My first decision when trying to solve labyrinths by image recognition is obviously…
ShizukaSM
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Is there a podspec for Opencv?

I have recently used Cocoapods - library dependency management tool in objective C. It has podspec for commonly used libraries like ZXing, AFNetworking etc. Have anyone come across Opencv podspec?
Skanda
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Computing Hamming weight, also called popcount in Java?

I am not sure how to translate this from C++ to Java. It is a function that computes the Hamming weight. /** This is popcount_3() from: * http://en.wikipedia.org/wiki/Hamming_weight */ unsigned int popcnt32(uint32_t n) const { n -= ((n >> 1) &…
user1796942
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Turn on Android display when someone approaches the device

Using a bit of computer vision, I'd like to turn on the display of a wall-mounted Android device when a human walks up to (w/in 2 feet of) the device. I'm an experienced developer, but I know next to nothing about computer vision. Programmatically…
David Pfeffer
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