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Questions tagged [image-compression]

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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coherence calculation in sparse sensing

i have an image I of size 32*32. I perform the DCT of this image using the matlab function DCT2(I). I get a sparse representation of my image which is again a 32*32 image. I construct a circulant ...
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How to determine a quantization table for image compression with DCT?

The quantization table is given on the JPEG Wiki page. How was this table derived? I'm currently doing a project where I have to come up with custom quantization table for an image, but I don't know ...
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“Image Processing” [closed]

I'm an Italian student. I'm studying Gnu Radio and I would like to upload a photo, can I upload it with "file image source" or other blocks? I need to make FFT of an a image. -> image 2D Thank you ...
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Do chroma signals add any information to luma in YUV?

Consider the YUV 422 picture format that I get from an image sensor. The luma (Y) carries 4 bits of grayscale information. Do the additional 2+2 bits of U+V add any additional info to the overall ...
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Facing problem in plotting histogram of DCT coefficient of an image

In digital image forensic, it is assumed that the histogram of DCT coefficients of the un-compressed natural image has the smooth histogram. However, the histogram of DCT coefficients of the ...
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How Does Mean Centering Affect the Result of Using SVD to Compress Images?

I have been learning about using the Singular Value Decomposition to find low rank approximations to matrices. I had an image which I converted to a matrix. I regarded each row of the matrix as a '...
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58 views

How to Approximate the File Size Ratio of Two JPEG-LS Compressed Images? [closed]

For instance, a high-resolution image (25MP) and a low-resolution image (4MP) of the same scene. When compressing them both with ...
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38 views

How Can JPEG Be Used to Realize a Transfer Application with a Fixed Bit Rate? [closed]

For simplicity, assume a fixed bandwidth (5MB/s) and that each second an image with 12MP is generated. The quality of the image ...
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Reconstructing image from the dwt coefficients

I am trying to compress and reconstruct an image but facing problems with the data type of the compressed image pixel values which are of float64 and therefore, when I am trying to retrieve the pixel ...
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1answer
131 views

SSIM(YUV) vs SSIM(Y): values very different

I'm seeing some weird results when trying to compare image qualities in a few different color spaces. Have a look at my graph: I want to compare with another publication, which reported PSNR(YUV) and ...
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1answer
30 views

Need a 2 parameter ranking system for image compression

I'm working on a project in which specific bit planes of an image are extracted and compressed. This process is repeated for every combination of bit planes possible.For an image, I have calculated ...
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Regarding compatibility of ISP's

I am working for an electric mobility startup and our aim is to produce electric cars with ADAS/autonomous-driving capabilities. Right now we are in the process of building a prototype. For meeting ...
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Which channel coding technique is suitable for wireless SPIHT compressed image: Reed-Solomon or convolutional code?

I want to transmit a SPIHT-based (Set Partitioning In Hierarchical Trees) image compressed image over a wireless fading channel, which will be suitable as channel coding technique: Reed-Solomon or ...
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Origin of brightness artifacts in intensity resolution compressed images

when compressing this image (It corresponds to Fig2.20 from the book Digital Image Processing by Gonzalez and Woods and the original .tif document can be downloaded through this link By reducing ...
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1answer
143 views

Confirming what a compression ratio is

I have looked at various sources, but still have not been able to answer the question: what is compression ratio? I have come to the understanding that this is the definitive answer: compression ...
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Quadtree decomposition of Discrete Wavelet Transform using bio4.4/CDF wavelet

My problem is pretty basic but fundamental. It relates to the way discrete wavelet transform behaves for biorothognal 4.4 or CDF wavelets. When using most wavelets (e.g., CDF 9/7 or bio4.4 or ...
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1answer
143 views

compression ratio of pixels block

I am new to image compression topic and really appreciate it if someone could help me understand how compression rati works in this case. Assuming I have JPEG lossless coder that encodes the following ...
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176 views

How to predict next image in a sequence, or predict the deblurring of an image?

I have 3 versions of an image at lower resolutions - 480p, 720p, and 1080p. Is it possible to use those 3 images to predict the next highest resolution image (the 4k image)? My first guess was that ...
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181 views

Compression ratio for 4x4 block

Say I have the following 4x4 block: [ 120 121 125 119 120 120 118 117 122 121 117 118 122 122 120 120] If this block is intra coded the ...
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1answer
2k views

Bit plane slicing in python

I recently came across a technique called bit-plane slicing for image compression in a book "Digital image processing" by gonzalez and woods . They just presented the theory and i wanted to ...
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2answers
382 views

Are the FFT coefficients symmetric in image processing?

On page 11 of Fundamentals of Image Processing by Ian T. Young, Jan J. Gerbrands, Lucas J. van Vliet (pdf) the results of the Fourier transform are shown (Figs 4a and 4b) and it appears to me (please ...
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468 views

Does a simple photograph contain more information than a complex painting?

I hope this question is appropriate for this site. I came across this passage in The Three Body Problem, a novel by Liu Cixin: The professor had put up two pictures: One was the famous Song ...
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140 views

How doesn't JPEG huffman table contain 256 codes?

Here are the DHT entries I got from JPEG snoop: ...
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1answer
679 views

Loss in converting YUV to PNG

I have a YUV 420NV12 image. I'm using ffmpeg to convert the YUV file to PNG and then back again to YUV. ...
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2answers
409 views

How does Jpeg encoding affect the final file size of 24BPP RGB and 8BPP grayscale image?

The reason I'd like to know this is because of a file size problem. I am trying to reduce an image's file size from converting it from TIFF to JPEG. A user challenge me that he notice a RGB TIFF image ...
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1answer
729 views

What are some good images to use when comparing image compression algorithms?

There was a question about images that are hard to compress. Are there images that are better suited to testing compression quality than others? Maybe an image of diagonal lines of specific colors at ...
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2answers
87 views

Fast method to decompress huffman and arithmetic encoded data

By nature, when decompressing huffman (and I assume also Arithmetic encoded data) we have to read it in bit by bit and then see how it traverses a huffman code tree that has the actual symbol value at ...
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1answer
165 views

Does every 8 by 8 DCT matrix have a valid (in range) IDCT?

For a given quantization level of JPEG compression, are all possible DCT matrices have valid IDCTs. By valid, I mean matrices whose elements are in the range [0,255] ?
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801 views

JPEG DCT padding

Since the JPEG DCT block used is 8x8, how does the method deal with images with dimensions that are not multiples of 8? What kind of padding does it use? How are the 8x8 blocks of the image chosen?
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1answer
42 views

What base image size to choose to assist easier downsizing?

Android applications need image at different resolutions to support different screen densities and pixel size. I am planning to provide only one image with high pixel size and let the underlying ...
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1answer
217 views
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113 views

What is this kind of distortion called?

Today while watching a movie I noticed the following distortion: Note. The red ring is me painting over to show the area of interest. There are certain areas in which I can see non-smooth shades of ...
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2answers
770 views

Random Noise Removal In Images

I'm trying to remove random noise from an image. The noise is arbitrarily random so it must not necessarily follow a certain distribution (Not every pixel has the same chance of being affected by ...
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How do I keep file size low when scanning a book (to create eBook version for smartphones)?

I have a printed book that I am planning to convert into digital version for smartphones. It has 600 pages and OCR/Retyping it is not possible (must use images). Tried various options but per page ...
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2answers
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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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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
100 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
2k 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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928 views

Why Wavelet based Transform 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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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
547 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
305 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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74 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
330 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
2k views

Image compression using SVD in MATLAB

I have to compress an image using SVD. I did a few things, but all of them produced a black & white image. However, the output must be RGB. How can I compress an image without changing its ...
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2answers
117 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
689 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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2answers
424 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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2answers
241 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
7k 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. ...