Search Results for "pngs"

Times change, with standards. The standard of internet web graphics now has to be replaced ith a new file type. With a 32KB sliding window PNGs uses the deflate compression algorithm typically. An improved version of the Lempel-Ziv compression algorithm (LZ77) used in ZIP and GZIP files (3,4) is deflate. Deflate Created by Phil Katz for version 2 of PKZip combines LZ77 with Huffman encoding and is 10% to 30% more efficient than LZW at lossless compression. Some PNG compression tools have an optional “compression ratio” with values ranging

In 1977 and 1978, two Israeli researchers, Jacob Ziv and Abraham Lempel worked on a set of compression algorithms, which were later named LZ77 and LZ78. Later, in 1983, Terry Welch from Sperry (which later merged with Burroughs to form Unisys) developed a very fast variant of LZ78 called LZW. Welch, together with two IBM researchers, Victor Miller and Mark Wegman, filled for a patent for LZW. At the same time, Compuserve, specifically Bob Berry, was designing a new algorithm for a compressed image format, where they used the LZW

There are many fantastic points and examples in this essay by Phillip Hoyt. One of the most unique items he brings up is the file type's abilities with regards to Gamma Correction. "From the LibPNG site: "Gamma correction basically refers to the ability to correct for differences in how computers (and especially computer monitors) interpret color values." There are two factors here: the ability to predict what an image, say a photograph, will look like on another monitor; and the ability to match the colours from different sources on a single page.