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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pixels in the same image are correlated but how can I visualize it?

I am new in image processing.I know that pixels in the same image are correlated with each other but I don't know how can I draw the relationship b/w these pixels in the form of graph?.
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15 views

Decompose an N x N 2D DCT into 4 N/2 DCT's

I have a fast implementation of a 16x16 DCT and IDCT in c++, I would like to know how to partition a 32 x 32 array of values and scale factors to implement a 32 x 32 DCT, and IDCT respectively. A ...
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0answers
17 views

Controlling the pursuit path of the human eye?

The human eye scans images by panning focus along a certain path. I've read that eye tracking studies have revealed that there is a feedback process involved in moving ocular focus along a path that ...
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2answers
52 views

How to choose basis functions that contribute most efficiently per term to an approximation of an image f(x,y)?

GOAL: I would like to approximate some positive, scalar function, $f(x,y) > 0$, on a 2D field of finite size i.e. $x=[a,b],y=[c,d]$ OBSTACLE: I am familiar with the set of basis functions used ...
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1answer
139 views

8*8 block matrix in JPEG image compression?

In standard JPEG format of a image, Discrete Cosine transform is used. But instead of applying the transform on whole image, we first divide the image in 8x8 block and apply transform on each of them. ...
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0answers
15 views

Mask shape in image DCT transform

I've been studying image compression using the FFT and DCT transforms. When using the FFT transform, it is customary to perform a frequency shift (fftshift) so that ...
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0answers
9 views

hdr compression using adaptive-learning codebook

I've implemented the following adaptive-learning algorithm for hdr image compression. paper can be found here I intend to work with grayscale images only. I get bad results, so I'm trying to find ...
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0answers
14 views

Why do we need to use matrix for quantization when we merely need a “comparator”

I have found that JPEG has different matrices for the quantization step which is also called truncation. I am confused, why do we need a matrix for quantization in 2D? That is not how quantization ...
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1answer
66 views

why wavelet is more suitable for image compression compared to DCT?

Everyone knows that JPEG2000 can obtain much better compression result than JPEG. The fundamental transform behind JPEG2000 is wavelet while the basic transform in JPEG is DCT. So my question is why ...
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2answers
43 views

Selective image compression?

Forgive me if this is the wrong site for this question. Here's my problem: I am creating a game where players have to search for a hidden detail within the overall image. I downloaded an 11MB ...
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2answers
112 views

Compare between JPEG and JPEG2000

JPEG image compression is Fourier based DCT while modern image compression technique like JPEG2000 is based on more multi-scale technique like Wavelets.I want to know how Fourier and Wavelets are ...
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1answer
107 views

Why don't DSLR cameras default to png instead of jpeg? [closed]

I'm working with a new DSLR camera for a Computer Vision application and I noticed most of them default to saving in the lossy JPEG format. Initially, this caused some problems in my application and I ...
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1answer
34 views

How does a wavelet help in image compression?

I understand how the discrete cosine transform is used in image compression in standards like JPEG. However, the concept of wavelets is a mystery to me. I do know that wavelets are functions that have ...
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1answer
116 views

What does it mean for an image to be “Markovian”?

I've been following the recent lectures on Coursera for image processing. In the lecture on the use of the discrete cosine transform (DCT) for image compression, he says that for images that are "...
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1answer
225 views

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
63 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
120 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
193 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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1answer
73 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
2k 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
57 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
364 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
63 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 ...
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2answers
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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
218 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
76 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
170 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
125 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 ...
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4answers
650 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 ...
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9answers
7k 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 ...
8
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3answers
852 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
248 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 ...