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Topic: Image compression


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  Image compression - Wikipedia, the free encyclopedia
Image compression is the application of data compression on digital images.
In effect, the objective is to reduce redundancy of the image data in order to be able to store or transmit data in an efficient form.
The quality of a compression method is often measured by the Peak signal-to-noise ratio.
en.wikipedia.org /wiki/Image_compression   (482 words)

  
 [2.0] JPEG Image Compression   (Site not responding. Last check: 2007-11-07)
Images are defined as either "realistic", meaning photographs or realistic artwork with many shades and few straight lines, or "nonrealistic", meaning graphs, block diagrams, graphics banners, and cartoons with block colors and many straight lines.
The best known lossless compressed image file scheme is Compuserve "Graphics Interchange Format (GIF)", which uses a variation of the lossless LZW compression algorithm as outlined in the previous chapter to compress images.
The image would be analyzed to determine the fractal patterns that make it up and transformed into relatively small and compact sets of parameters that define the proper fractal algorithms, The parameters could then be further compressed with some lossless compression algorithm, in principle resulting in a very compact graphics file.
www.vectorsite.net /ttdcmp2.html#m3   (6290 words)

  
 An Introduction to Image Compression
An approximation of the original image is enough for most purposes, as long as the error between the original and the compressed image is tolerable.
The MSE is the cumulative squared error between the compressed and the original image, whereas PSNR is a measure of the peak error.
One example is the Fractal Image Compression technique, where possible self similarity within the image is identified and used to reduce the amount of data required to reproduce the image.
www.debugmode.com /imagecmp   (583 words)

  
 Image and Video Compression Techniques
The images shown on the screen are irrelevant such that a random noise image requires the same bit rate as a blank image.
Images scanned from the television camera are compared with the current image in the Image Buffer to locate pixels that have changed brightness.
The image in the Image Buffer is periodically scanned to the output monitor.
www.autosophy.com /videcomp.htm   (5727 words)

  
 Image Compression using Backprop
By using data compression techniques, it is possible to remove some of the redundant information contained in images, requiring less storage space and less time to transmit.
To compute the amount of image compression (measured in bits-per-pixel) for this level of quantization, we compute the ratio of the total number of bits transmitted: to the total number of pixels in the original image: 64; so in this case, the compression rate is given as bits/pixel.
Training input-output pairs are produced from the training image by extracting small 8x8 chunks of the image chosen at a uniformly random location in the image.
neuron.eng.wayne.edu /bpImageCompression9PLUS/bp9PLUS.html   (740 words)

  
 Optimizing Web Graphics: Compression - webreference.com
The "vertical" image is nearly identical in size to the "horizontal" one, which shows that PNGs are not sensitive to vertical noise.
Compression and decompression times are symmetric, although the International JPEG Group's (IJG) decoder is more optimized and noticeably faster than their encoder.
JPEG compression takes place in Y/UV space and therefore is treated as 24 bit data (8 bit for grey), regardless of the colors in the original image.
www.webreference.com /dev/graphics/compress.html   (3862 words)

  
 SITO compression page
With respects to images on SITO, effeciency is a matter of choosing an appropriate physical dimension for an image, and choosing the compression method or format that yeilds the best results.
The larger the size of an image, the longer it takes to download, which means a person gets to see a relatively small number of images if they are too large.
GIF has additional "LZW" compression built in, but LZW doesn't work very well on typical photographic data; at most you may get 5:1 compression overall, and it's not at all uncommon for LZW to be a net loss (less than 3:1 overall compression).
www.ibiblio.org /otis/notes/otis-compression.html   (2313 words)

  
 Compression: Digital Imaging: Glossary: Learn: Digital Photography Review
For instance, if you compress a document into a ZIP file and later extract and open the document, the content will of course be identical to the original.
Lossy compression reduces the image size by discarding information and is similar to summarizing a document.
JPEG is an image format that is based on lossy compression.
www.dpreview.com /learn?/Glossary/Digital_Imaging/Compression_01.htm   (326 words)

  
 JPEG image compression FAQ, part 1/2
GIF has additional "LZW" compression built in, but LZW doesn't work very well on typical photographic data; at most you may get 5:1 compression overall, and it's not at all uncommon for LZW to be a net loss (i.e., less than 3:1 overall compression).
In fact, a user viewing such an image on a browser with a 256-color display is unlikely to be able to see any difference from a higher quality setting, because the browser's color quantization artifacts will swamp any imperfections in the JPEG image itself.
If you enlarge the image, you will find that adjacent pixels are often of significantly different colors; at normal size the eye averages these pixels together to produce the illusion of an intermediate color value.
www.faqs.org /faqs/jpeg-faq/part1   (9116 words)

  
 Catalog Page for PIA07585   (Site not responding. Last check: 2007-11-07)
Due to the compression, the image retains a blocky, or "pixilated," quality after enhancement.
Despite these artifacts, such compression can be useful for increasing the number of images that can be taken and relayed back to Earth.
The image was taken with the Cassini spacecraft wide-angle camera on July 31, 2005, using a filter sensitive to wavelengths of infrared light centered at 728 nanometers at a distance of approximately 1.3 million kilometers (800,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 35 degrees.
photojournal.jpl.nasa.gov /catalog/PIA07585   (284 words)

  
 Fractal Image Encoding
biblio.ps.gz is a bibliography focused on fractal image compression particularly.
The Waterloo Fractal Compression Project is part of a general research programme dedicated to the study of fractal analysis and Iterated Function Systems/Fractal Transforms from both theoretical as well as practical perspectives.
The report is called "Digital image compression with two-dimensional affine fractal interpolation functions," which sums up the approach (to be brief: encoding is done on scanlines, with an iterative ``chaos game'' decoding).
inls.ucsd.edu /~fisher/Fractals   (4079 words)

  
 Image Compression   (Site not responding. Last check: 2007-11-07)
One fundamental property of images is that each pel is usually similar to its neighbours, so it is usually possible to predict what it will be from previous pels.
Although the errors are introduced mainly in the higher frequencies, this means that at lower quality images might not have sufficient high frequancies to "join-up" at the 8x8 block edges.
The difference between an image and a version half its size is in fact a range of distinct frequencies in the image.
www.ecs.soton.ac.uk /~km/teaching/compression   (1136 words)

  
 Compression Research
A set of experiments was performed with a lossy image compression algorithm that utilizes non-uniform sampling and interpolation (NSI) of the image intensity surface.
The goal of this work was to create a lossy compression algorithm which was asymmetrical, having a low decompression complexity and a potentially higher compression complexity.
The number of samples chosen, and hence the compression ratio, is based on a supplied error metric threshold and local image features.
www.cs.cmu.edu /~chuck/nsipg/nsi.html   (487 words)

  
 Image Compression Toolbox v1.2
Image Compression Toolbox is a collection of routines commonly used in image compression.
Quantization of the image data using a uniform quantizer, which is implemented as the UniformQuant class.
It was the starting point for me to learn all about image compression.
www.debugmode.com /imagecmp/icomptbx.htm   (238 words)

  
 The FBI Fingerprint Image Compression Standard
That implies lossy compression, which means we're going to have to tolerate some distortion in the compressed images.
The white spots in the middle of the fl ridges are sweat pores, and they're admissible points of identification in court, as are the little fl flesh ``islands'' in the grooves between the ridges.
Since these details are just a couple pixels wide, our compression method needs to preserve features right at the resolution of the scan, a VERY tough problem since most lossy algorithms work by throwing out the smallest (or highest frequency) details in the image.
www.c3.lanl.gov /~brislawn/FBI/FBI.html   (713 words)

  
 xat.com: GIF JPEG Compression software download, JPEG Optimizer, Image Optimiser, Slide Show/Screensaver for PC and ...
Image Optimizer Get the best possible GIF and JPEG image compression for web graphics.
Resize, compress and watermark images as they arrive at your server or compress a whole site/disk.
Image Optimizer OCX Integrate xat.com image compression and enhancement technology with your Visual Basic, Delphi etc application using our OCX activex control.
www.xat.com   (448 words)

  
 Freeware downloads Graphics Tools - Image Compression at SnapFiles.com
Simple little application which removes the unused colors from GIF image pallets reducing the image size, This also works with animate...
Miliki Super Compressor Pro compresses documents and images at an amazing rate that results in files that are up to 10 times smaller t...
The program can process selected files or entire folders (with subfolders) and process images and HTML files at the same time, allowing webmasters to optimize their entire site in a single run.
www.snapfiles.com /freeware/gmm/fwgcomp.html   (615 words)

  
 Amazon.com: Fractal Image Compression: Theory and Application: Books: Yuval Fisher   (Site not responding. Last check: 2007-11-07)
Presents the theory and application of new methods of image compression based on self-transformations of an image.
Elementary introduction to the concept of fractal image compression.
Anyway, after reading the book, I was able to create some nice code and to compress color images up to 1:25...
www.amazon.com /exec/obidos/tg/detail/-/0387942114?v=glance   (711 words)

  
 StuffIt - NEW Image Compression Technology!
The only solution was to further reduce the quality of the image in a graphic editing application.
The exclusive new image compression technology in StuffIt Deluxe now allows you to reduce the file size of your JPEG images WITHOUT reducing the quality of the image!
Whether you’re taking pictures of the kids to share with your friends and family, or taking photos for a living, StuffIt’s image compression technology has something to offer.
www.stuffit.com /imagecompression   (228 words)

  
 SPINWAVE -- GIF and JPEG Compression and Optimization
Click here for free, low compression crunches using JPEG Cruncher and GIF Cruncher, the most popular optimization software tools on the web.
Compress your JPEGs and GIFs to shrink file size, make your web site faster, save disk space, and generally relieve an overcrowded world!
Subscribe to the Spinwave image optimization newsletter for tips and tutorials on how to get the most from your GIF and JPEG images.
www.spinwave.com   (248 words)

  
 SPIHT Image Compression   (Site not responding. Last check: 2007-11-07)
Image Compression with Set Partitioning in Hierarchical Trees
Welcome to the WWW home page that describes Set Partitioning in Hierarchical Trees (SPIHT): the award-winning wavelet-based image compression method.
These pages are being served from the Center for Image Processing Research (CIPR) at the Rensselaer Polytechnic Institute (RPI).
www.cipr.rpi.edu /research/SPIHT   (158 words)

  
 Lossless Image Compression Links
MG System - mg system, described in the book Managing Gigabytes contains the implementation of FELICS
List of Image and Graphics File Archives from Graphic File Formats FAQ
Wotsit's Format: The programmer's file formats and data formats resource.
theory.cs.uni-bonn.de /~yasha/limcomplinks.html   (108 words)

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