Tagged Questions

image compression is a process of representing an image file or datastream using fewer bytes. compression can be "lossless", in which the original data can be recovered exactly, or it can be "lossy", in which some detail is lost for the sake of better compression.

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A question about image compression with SVD - MATLAB

I have to compress an image by using svd. I did a few things but all of them produced gray image. However, Output must be rgb. How can i compress an image without changing its original format?
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2answers
28 views

How does using DCT help in image compression

I once learnt that the Huffman Encoding is used to rid of redundant information, thus reducing file size. I am not sure how using a DCT, or FFT on an image can help in reducing file size. It does not ...
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1answer
84 views

What is the Difference between Texture and Image?

I am beginner in the image processing I want to know what is difference between Texture and Image? or whether they are same? can anyone explain it. Also,if i want to do texture segmentation,can i ...
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1answer
52 views

Confusion about shannon's entropy of the grayscale image after lossy compression

I have a .pgm format 480 * 640 gray scale image named 'columns.pgm'. Using PCA (principal component analysis), by preserving 40 principal components I compressed original image with 1218 KB to 301 KB ...
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0answers
32 views

How to apply dictionary learning to several images?

I'm implementing a dictionary learning algorithm for doing sparse coding on images and I have a problem how to learn a dictionary corresponding to several iamges. Let’s say X is the data matrix. If I ...
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1answer
227 views

What does the 420 means in YUV420?

I'm not sure if is the correct location for ask this question. If not please info me the correct StackExchange site. As this wikipedia page show, there is one YUV format of image as YUV420 and YUV411. ...
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1answer
22 views

PNG IDAT specification

I'm going over the W3 PNG specification (creating a PNG library from scratch) and I've finally found how to create a green 1x1 image. Now I'm trying to create a bigger image of mixed Red, Green and ...
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2answers
324 views

Difference between jpg compression and mp3 compression

My understanding of jpg compression is that, if done repeatedly, any image will eventually be reduced to a single flat color, due to the way it deals with neighboring pixels. However, years ago I was ...
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0answers
57 views

reducing chroma of image on client and reconstructing on server

I have a C# desktop application. I am using Emgu wrapper to openCV. My objective is to upload images in the most efficient way I can. I have hit upon the idea of loading an image (jpeg) into memory ...
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0answers
48 views

Sparsity limits of compressed sensing - is this right?

Compressed sensing (CS) guarantees exact object recovery (or with high probability) given a) sufficient measurements are taken in a sparse basis which is b) incoherent vis-a-vis a given object ...
6
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2answers
520 views

What is the Compression Algorithm used by Facebook?

I would like to know what is the Compression Algorithm used by Facebook for compressing the images? I uploaded a image of size 242 Kb and I downloaded the same image from my Facebook album. The size ...
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2answers
151 views

In image compression using transforms,how to deal with the transformed coefficients as they are not integers?

I am new to the field of image compression. While going through various texts, I read about how transforming the image to another domain using, for example, the wavelet transform, or the DCT, makes it ...
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1answer
53 views

What are some techniques to recover an original image from three different compressed versions?

This question is theoretical. Let's say you have three different highly compressed images of a same source image, each compressed with a different algorithm and thus "lossy" in different ways. What ...
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1answer
131 views

Lossless algorithm for hyperspectral imaging

I am looking for Lossless compression algorithm for hyperspectral imaging. The only one that I found was LPVQ. Do you know other algorithms? I am looking for pseudocode or matlab code. Thanks
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0answers
81 views

How does Golomb-Rice Coding work?

I've read the explanation in http://urchin.earth.li/~twic/Golomb-Rice_Coding.html and http://en.wikipedia.org/wiki/Golomb_coding , however, I still not get the intuition why it is efficient and when ...
12
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3answers
565 views

applicability of compressed sensing

From what I have heard, compressed sensing can only be utilized for a sparse signal. Is this correct? If that is the case, how can a sparse signal be distinguished from any bandlimited signal? Every ...
22
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5answers
2k views

What is the least JPG-compressible pattern? (camera shooting piece of cloth, scale/angle/lighting may vary)

I am trying to design a cloth that, from the point of view of a camera, is very difficult to compress with JPG, resulting in big-size files (or leading to low image quality if file size is fixed). It ...
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3answers
480 views

Simple, streaming, lossless image compression

Does anyone know of any image compression techniques with the following characteristics: lossless streaming - I want to compress on the fly, pixel-by-pixel. low-memory overhead - I can afford to ...
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3answers
216 views

Skip corrupt part of jpeg

Is it possible to read a JPEG file and skip parts that are corrupt? I have three corrupt JPEG files and I can detect the first corrupt block, but can I skip it and continue with the next block? I ...