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Questions tagged [image-processing]

The tag has no usage guidance.

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find the actual size of an object from pixel coordinates

I am quite new to vision and OpenCV, so forgive me if this is a stupid question but I have got really confused. My aim is to detect an object in an image and estimate its actual size. Assume for now ...
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1answer
281 views

How to test image segmentation algorithms? [closed]

What would be an ideal environment/manner to judge the effectiveness of multiple segmentation algorithms? The goal is to determine which algorithms provide the best results for pre-clinical imaging. ...
1
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1answer
882 views

How do I detect and rotate a square?

I have recently written code for detecting path colors in a 2D grid and printing the corresponding path costs and it works fine for me. Here's my code; I am currently new to OpenCV and know only C++ (...
-1
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1answer
162 views

How to identify and find navels from human pics

I have a specific question and not sure what tools I can use to finish my projects. I know this may has been well solved, but I am quite new to the image recognition and detection area and don't know ...
5
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1answer
797 views

How to calculate Huffman code length without generating the actual huffman code?

Given a vector of elements, how can I calculate the length of the Huffman codewords without generating the Huffman code itself? Using Matlab, I was able to compute the Huffman code and and get the ...
2
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1answer
744 views

Compare phase and magnitude spectrum results of 2 Images

I have read that from Fourier transform we obtain magnitude and phase spectrum. The magnitude spectrum tells you how strong are the harmonics in a image and the phase spectrum tells where this ...
4
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1answer
6k views

The Fundamental and Essential Matrix

Could someone, in plain english, explain the distinction between the fundamental matrix and the essential matrix in multi-view computer vision? How are they different, and how can each be used in ...
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0answers
176 views

Computer vision training procedures: SVM/AdaBoost vs Neural Networks

With SVM, adaboost or similar alogrithms, image training sets must be cropped with specific constraints (keep image cropping ratio the same, have object tightly cropped, same resolution) In general, ...
2
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1answer
265 views

Can you determine rotation/camera calibration from series of images separated by pure rotation

I have a series of about 50 images, each separated by a small rotation and taken from the same camera. The images are feature-dense, and I can calculate a homography from image-to-image easily. My ...
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2answers
137 views

Is there a way to tell a picture has been resized?

I need to evaluate if the picture was resized (upscaled). Are there any approaches to that already? If not, what do you recommend me to start with?
0
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1answer
40 views

What is the exact definition of a dictionary in the concept of linear algebra and computer science?

I am reading this paper for my master thesis and trying to understand every concept in it. The following sentence confuses me as to what is the exact definition of a dictionary in this concept except ...
-3
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2answers
132 views

Digital Image Processing [closed]

I'm a Computer Science Graduate but I didn't study digital image processing during my college years. Now I'm thinking of learning it, but I'm little bit confused about where to start. Is there any ...
2
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1answer
478 views

How to Know Whether a Topic is Publishable in Computer Science

Forgive my ignorance, but I am very new to the publishing process in Computer Science. I have some research that I have done involving analyzing data formats used in web-based image processing ...
2
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1answer
773 views

How can GIF compression be lossless if the maximum # of colors is 256?

I'm reading "Computer Science Made Simple" by V. Anton Spraul, and in the chapter about Graphics, he describes GIF files as follows: A GIF file uses lossless compression to store an image with a ...
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0answers
210 views

How to identify the z-ordering of objects in a computer vision or image processing scene?

Given that there is an image with objects in it, is there any method in computer vision to determine the z-ordering of objects. For an ideal image of three circles overlapping, I can determine that it ...
0
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1answer
317 views

Blob detection as Constraint satisfaction problem?

In image processing I have a black and white image which is represented by matrix {0,1}, I have to find blob (a region of connected pixels) in it. I'm confused, can this problem be reduced to ...
4
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1answer
447 views

Efficient flood filling (seed filling)

I am referring to the algorithm that fills a white area of arbitrary shape in a binary digital image, starting from a given white pixel, using the Moore (8 neighbors) or Neumann (4 neighbors) ...
6
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2answers
47 views

Determining width of paths

I have an image, like the one below that has different paths. I want to be able to detect the thin parts of these paths and highlight them. What is the best way to go about this?
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1answer
490 views

Finding approximately collinear points

my issue comes from image processing. The image below is for a better understanding of the problem. I have to detect three dots (shown in black, marked with red arrows). The other points I get from my ...
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0answers
150 views

Technique behind the way google earth overlaps polygons on top of pictures

What´s the technique behind the way google earth overlaps polygons on top of pictures(like the ones users assign to streets and houses) ? It seems to be aware of perspective, and I don´t remember ...
3
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0answers
203 views

Simplify closed-path points without intruding into the inside of the path

I want to: Simplify a set of points that outlines a closed opaque image on a transparent background. The simplified set of points should not intrude into the closed opaque image. I use a Marching ...
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0answers
737 views

Improving MSE as fitness function for a genetic algorithm

I am implementing an autoencoder neural network in matlab, the weights of which are being optimised by a genetic algorithm. At the moment I am working on the first layer, trying to get an improved ...
3
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2answers
878 views

Extracting features for texture classification

I'm a beginner in the field of pattern recognition and computer vision. I'm working on a project right now to classify t-shirt patterns into three categories i.e. solids, stripes and checks. I have ...
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1answer
84 views

Selecting a M.S. in CS focus [closed]

I need to pick a focus in my Masters program. The running candidates are Networking Bioinformatics Data mining Computer Image Recognition In order to avoid this becoming a discussion, I'd be ...
4
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1answer
1k views

Training and testing image sizes for classification in computer vision

When training a classifier for object detection using features extracted from images (eg HoG features), how important is it that the images used for training fed into the classifier in their natural ...
2
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1answer
387 views

Method to recognize abstract objects such as hand-drawn objects?

My research is in the area of Document Image Analysis. To be specific, the topic of my thesis is to automatically recognize and index characters in a set of hand-drawn objects, e.g. given a volume of ...
6
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2answers
745 views

What are all the differences between the Gibbs phenomenon artefects and JPEG artefacts?

I thought the Gibbs phenomenom is the result of Fourier analysis estimation (but was it Fourier Series estimation or can it also be Fourier Transform estimation?) JPEG uses the Discrete cosines ...
2
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1answer
117 views

Resizing and aliasing in computer science [closed]

If you resize an 1000x1000 raster image to 10x10 and resize it back to 1000x1000 is this considered to be an example of aliasing?
9
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1answer
222 views

Recognizing waterways in an aerial photo — polygons from edge detection images

I am trying to recognize waterways from aerial photographs (say from Google Maps). Local governments often have GIS data that says where the waterways (and roads, buildings etc) are, but the water ...
3
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2answers
349 views

How do I apply patch sized features to larger images?

I've been trying to teach myself some machine learning, and I wanted to ask what seems a simple question, but I've not been able to find any resources that explain the next step. Let's say I am doing ...
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1answer
317 views

How to compute Gabor feature vector?

I'm working on semi automatic texture segmentation using level set and gabor feature vector described by Manjunath und Ma [1]. I consider their feature representation is better than others since I can ...
1
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1answer
853 views

Number of different output labels in Local Binary Pattern

I'm studying about Local Binary Pattern and I'm having trouble understanding the following part about the number of output labels for binary patterns from Computer Vision using Local Binary Patterns, ...
2
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1answer
1k views

How to count near circular objects in image

I have a image similar to below. In that I need to find all red circles and count them. So, I am thinking to use MATLAB R2011a with Image Processing Toolkit for it. How could I possibly extract them?
3
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1answer
77 views

How to evaluate the accuracy of a method for the extraction of the principal lines of the palmprint

Let's assume that I've implemented a method for the extraction of the principal lines of the palmprint. For instance, let's say that I'm able to do a transformation like the following one (image from ...
2
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4answers
582 views

Environment detection - How to detect “city” versus “landscape” background environment in computer vision?

I'm searching for computer vision or machine learning algorithms/methods that are used to classify or differentiate two outdoor environments. Given an image with vehicles, I need to be able to detect ...
2
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1answer
566 views

Making feature vector from Gabor filters for classification

My aim is to classify types of cars (Sedans,SUV,Hatchbacks) and earlier I was using corner features for classification but it didn't work out very well so now I am trying Gabor features. code from ...
3
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1answer
102 views

Environment requirement in training image dataset for classifier

I have a question about preparing the dataset of positive samples for a cascaded classifier that will be used for object detection. As positive samples, I have been given 3 sets of images: a set of ...
6
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1answer
3k views

Which algorithms are usable for heatmaps and what are their pros and cons

This is a cross post from Stack Overflow, and DSP at Stackexchange since I cannot really decide which part of Stackexchange is most fitting. If this is the wrong place please tell me and I'll remove ...
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1answer
93 views

Job sites for applied/interdisciplinary mathematics related to computer science? [closed]

I'm looking for job sites in applied/interdisciplinary mathematics, more specially, say postdocs or higher positions in mathematics and medical imaging, mathematics and computer vision. I'm aware of ...
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2answers
2k views

Object recognition - given an image, does it contain a particular 3D object of interest?

I have in mind a particular 3D object. Given an image taken by a camera, I want to check whether that image contains an instance of my object. For instance, let's say that the object is a bathroom ...
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1answer
2k views

Deriving the Sobel equations from derivatives

Many sites give the Sobel operators as the convolution mask for smoothing an image. However, I haven't found a single site that describes how you can derive the operators from partial first ...
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5answers
2k views

Where can a student learn image processing?

I am a student of computer science with interest in image processing. I have learned how to apply a few effects to images like making them grayscale, sketching them out of lines, etc. I would like ...
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1answer
1k views

circle packing algorithm used by Percolator

I was admiring this rendition of the Mona Lisa from quasimondo's Flickr account. He says: Combining circle packing with data visualization. The pie charts show the distribution of the dominant ...
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1answer
50 views

How can you see which points in the spectrum is from which pixel in the original image?

Take the image and spectrum below. If I look at the spectrum, it just look like noise.... How to make sense of it intuitively? Image: Frequency spectrum of image (using Fourier Transform):
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1answer
2k views

What the difference between the Fourier Transform of an image and an image histogram?

Consider this small picture of a sunflower, and its histogram: What would the Fourier transform of the first picture look like? Is there any relationship between the histogram and the Fourier ...
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1answer
5k views

2D convolution: Flipping the kernel?

Why do we need to flip the kernel in 2D convolution in the first place? What's the benefit of this? So, why can't we leave it unflipped? http://www.songho.ca/dsp/convolution/convolution2d_example.html ...
3
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1answer
629 views

Identifying an object in an image based on color (AI ?)

First off, I am not sure if this is the correct stackexchange site to ask this question on, so moderators can feel free to move it. I am working on an application that identifies an object in an ...
6
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0answers
465 views

Space filling between random 2D lines

Note that I had asked this question in GIS forum, although it has gotten many up-votes, still has not received any answer. Hope you can break the silence, some collaboration :) Consider a region (...
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2answers
3k views

Why is the laplace transform not popular for image processing convolution?

Why is the laplace transform not popular for image processing convolution? Most textbooks only conver the Fourier transforms.
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2answers
151 views

Mathmatical way to represent an image kernel?

How to represent the calculation in this image mathematically? For example: With the discrete convolution $(f * g)[n]\ \stackrel{\mathrm{}}{=}\ \sum_{m=-\infty}^\infty f[m]\, g[n - m]$ and Fourier ...