Archive : 10 Jun 2005 to 1 Aug 2005

In this archive page, you can find what Universpace thought was appropriate for the above mentioned period.

Current topics under discussion

Image and data compression

Support ogg-vorbis audio ; bye bye mp3!

Compressing an image is significantly different than compressing raw binary data. Of course, general purpose compression programs can be used to compress images, but the result is less than optimal. This is because images have certain statistical properties which can be exploited by encoders specifically designed for them. Also, some of the finer details in the image can be sacrificed for the sake of saving a little more bandwidth or storage space. This also means that lossy compression techniques can be used in this area.

Image Compression

Having read the above, One might be wondering how to obtain maximum compression without any significant loss in data.. The answer is right here and a simple one too!!

Even though loss-less compression techniques provide some amount of compression , they are not optimal enough. Hence, we switch over to the so-called lossy compression techniques.
This is acheived by JPEG / GIF compression.

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What is JPEG? JPEG stands for "Joint Pictures Experts Group " , Named after the group that originally formulated the algorithm for this compression
JPEG compression is applied only to images.
A similar technique has been developed for images , which is called MPEG.

JPEG is a lossy compression technique, which means that the image after compression will not be the same as the original image.

Due to it's optimal compression , JPEG has been chosen as the image compression standard.

How the JPEG works... Contrary to the popular belief about JPEG's algorithmic complexity , it is rather simple at its roots. It basically consists of an 8 by 8 window which samples the given image space repeatedly for its luminescence and chrominance.
Then this so constructed matrix is adjusted based on the parameters set(quality..size)
Then , a discrete cosine transform is performed on this matrix.
consequently , the so obtained values are rounded to the nearest integer values
Next comes the compression part , wherein Huffman algorithm is often applied.
So ,that's all to JPEG compression

The Universpace verdict... JPEG is real good when humans are viewing the image (because they don't notice small changes in color compared to small changes in brightness) ..
Download the text file containing the observations of the author regarding image compression if you want more info.
[image-compression.txt : file size < 1 KB] [Top]

Topic Archive : JPEG / Image compression

Archive : 10 Jun 2005 to 1 Aug 2005

Current topics under discussion

Image and data compression