Question: Mark Adler is best known for authoring the Adler 32 checksum fuction and his contributions to what type of image format?
Context: The Apple Icon Image format is the icon format used in Apple Inc.'s macOS.  It supports icons of 16 × 16, 32 × 32, 48 × 48, 128 × 128, 256 × 256, 512 × 512, and 1024 × 1024 pixels, with both 1- and 8-bit alpha channels and multiple image states (example: open and closed folders).  The fixed-size icons can be scaled by the operating system and displayed at any intermediate size. gzip is a file format and a software application used for file compression and decompression.  The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and intended for use by GNU (the "g" is from "GNU").  Version 0.1 was first publicly released on 31 October 1992, and version 1.0 followed in February 1993. Timarit.is (also known as Tidarrit.fo and Aviisitoqqat.gl) is an open access digital library run by the National and University Library of Iceland which hosts digital editions of newspapers and magazines published in Iceland, Faroe Islands and Greenland as well as publications in their languages elsewhere, such as Canada which had a large influx of Icelanders in the late 19th and early 20th centuries.  The project was initially sponsored by the West Nordic Council and launched its web interface under the title VESTNORD in 2002.  The web interface has since undergone two major revisions, in 2003 and 2008.  With the last revision a decision was made to gradually convert images from the DjVu image format to the more common PDF.  Hence, part of the collection can be viewed with the DjVu plugin and part with a PDF reader. The Graphics Interchange Format (better known by its acronym GIF or ) is a bitmap image format that was developed by US-based software writer Steve Wilhite while working at the bulletin board service (BBS) provider CompuServe on June 15, 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability. MTV ray tracer bitmap refers to the output format of the MTV ray tracer program by Mark T. VandeWettering.  It is a simple uncompressed true color raster image format, similar to binary PPM format.  Its name comes from the author's initials, and has no connection with the television channel MTV. Steven Adler (born Michael Coletti; January 22, 1965) is an American musician.  He is best known as the former drummer and co-songwriter of the hard rock band Guns N' Roses, with whom he achieved worldwide success in the late 1980s.  Adler was fired from Guns N' Roses over his heroin addiction in 1990, following which he reformed his old band Road Crew and briefly joined BulletBoys, which both proved unsuccessful.  During the 2000s, Adler was the drummer of the band Adler's Appetite, and from 2012, he had held the same position in the band Adler.  In early 2017, Steven Adler declared that he has no intention to continue with the band, and that the band has now dissolved, and the reason is his lack of interest in performing during poorly attended concerts.  He appeared on the second and fifth seasons of the reality TV show "Celebrity Rehab with Dr. Drew", as well as on the first season of its spin-off "Sober House".  He was inducted into the Rock and Roll Hall of Fame in 2012 as a member of Guns N' Roses. InteLex Past Masters is a collection of full text web-based scholarly editions of classic works in the humanities.  InteLex Corporation was founded in 1989 by its current CEO, Mark Rooks, in order to produce electronic versions of the works of the great philosophers, based on existing scholarly editions.  The company is located in Charlottesville, Virginia.  Its databases are marketed to academic institutions, with pricing based on the individual collections purchased.  Content is provided in XML and searchable image format and is accessed through the InteLex Corporation website.  In addition to philosophy, subject coverage includes religious studies, women's writing, social science, and history of science.  InteLex databases are found in institutions in over 60 countries around the world. Mark Adler (born April 3, 1959) is an American software engineer, and has been heavily involved in space exploration.  He is best known for his work in the field of data compression as the author of the Adler-32 checksum function, and a co-author of the zlib compression library and gzip.  He has contributed to Info-ZIP, and has participated in developing the Portable Network Graphics (PNG) image format. Adler-32 is a checksum algorithm which was invented by Mark Adler in 1995, and is a modification of the Fletcher checksum.  Compared to a cyclic redundancy check of the same length, it trades reliability for speed (preferring the latter).  Adler-32 is more reliable than Fletcher-16, and slightly less reliable than Fletcher-32. Guillermo Sapiro (born 1966) is a computer scientist, electrical engineer and professor who has made notable contributions to image processing.  He worked at The University of Minnesota for 15 years before becoming a professor at Duke University.  He has also worked at Hewlett Packard Labs (HP Laboratories) researching image processing and is known for being one of the people who originally developed the LOCO-I Compression Algorithm for lossless image compression (that was used in NASA's ICER image file format for various Mars rover expeditions) while he was working there.  He has also made significant contributions towards the development of the rotobrush tool in Adobe After Effects, which has been included in After Effects since version CS5.  Adobe makes use of his research in various projects like Photoshop and also frequently hires his students.  He also teaches a massive open online course through Coursera on image and video processing.  The title of the course is "Image and video processing: From Mars to Hollywood with a stop at the hospital."  He lives with his wife, two sons, and a very fat golden retriever named Hummus.
Answer: Portable Network Graphics (PNG)