PNG compression

PNG compression
Name	PNG
Extension	.png
Owner	World Wide Web Consortium
Standard	RFC 2083

PNG compression is a method of reducing the size of Portable Network Graphics files, which are widely used on the Internet by websites such as Wikipedia, Google, and Facebook. The development of PNG compression is attributed to the work of CompuServe, Adobe Systems, and the World Wide Web Consortium, which aimed to create a format that could replace the GIF format developed by CompuServe. PNG compression is based on the DEFLATE algorithm, which is also used by gzip and zip compression tools developed by Jean-loup Gailly and Mark Adler. The use of PNG compression has become widespread, with support from popular web browsers such as Google Chrome, Mozilla Firefox, and Microsoft Edge.

Introduction to PNG Compression

PNG compression is a lossless compression method, which means that the compressed image is identical to the original image, unlike JPEG compression used by Nikon and Canon cameras, which is a lossy compression method. The PNG format was designed to be a replacement for the GIF format, which was patented by CompuServe and required royalties to be paid for its use, as seen in the Unisys patent case. The development of PNG compression involved the work of several individuals and organizations, including Lee Daniel Crocker, Oliver Fromme, and the World Wide Web Consortium, which published the RFC 2083 standard for PNG. PNG compression is widely supported by image editing software such as Adobe Photoshop and GIMP, and is used by websites such as YouTube, Flickr, and Instagram.

Principles of Lossless Compression

Lossless compression, used in PNG compression, is based on the principle of representing data in a more compact form without losing any information, as described by Claude Shannon and David A. Huffman. This is achieved through the use of algorithms such as Huffman coding and Lempel-Ziv-Welch compression, which are also used by LZW and LZ77 compression tools developed by Abraham Lempel and Jacob Ziv. The DEFLATE algorithm used in PNG compression is a combination of LZ77 and Huffman coding, which provides a good balance between compression ratio and speed, as seen in the gzip and zip compression tools. The use of lossless compression in PNG compression ensures that the compressed image is identical to the original image, making it suitable for applications such as medical imaging and graphic design, which require high-quality images.

PNG File Format

The PNG file format consists of a series of chunks, each of which contains a specific type of data, such as the image data, metadata, and compression information, as described by the World Wide Web Consortium and RFC 2083. The PNG file format is designed to be extensible, allowing new chunks to be added as needed, as seen in the APNG format developed by Mozilla Corporation. The PNG file format is also designed to be platform-independent, making it possible to transfer PNG files between different operating systems such as Windows, macOS, and Linux. The use of PNG compression in the PNG file format reduces the size of the file, making it easier to transfer and store, as seen in the Google Drive and Dropbox cloud storage services.

Compression Algorithms

The compression algorithms used in PNG compression are based on the DEFLATE algorithm, which is a combination of LZ77 and Huffman coding, as described by Phil Katz and Jean-loup Gailly. The DEFLATE algorithm is widely used in compression tools such as gzip and zip, and is also used in other formats such as PDF and PostScript, developed by Adobe Systems. The use of compression algorithms in PNG compression reduces the size of the file, making it easier to transfer and store, as seen in the Amazon S3 and Microsoft Azure cloud storage services. The compression algorithms used in PNG compression are also used in other applications such as data compression and cryptography, as seen in the AES and RSA algorithms developed by National Institute of Standards and Technology and RSA Security.

Optimizing PNG Compression

Optimizing PNG compression involves using techniques such as image quantization and color reduction, which reduce the amount of data in the image, as described by Adobe Systems and GIMP. The use of optimization techniques in PNG compression can significantly reduce the size of the file, making it easier to transfer and store, as seen in the Google PageSpeed and Yahoo! Smush.it optimization tools. The optimization of PNG compression is also important for web applications, where fast page loading times are critical, as seen in the Google Search and Bing search engines. The use of optimization techniques in PNG compression is also used in other applications such as video compression and audio compression, as seen in the H.264 and MP3 formats developed by ITU-T and Fraunhofer IIS.

Comparison with Other Formats

PNG compression is often compared to other image compression formats such as JPEG and GIF, developed by Joint Photographic Experts Group and CompuServe. The choice of format depends on the specific application and the type of image being compressed, as seen in the Wikipedia and Wikimedia Commons image repositories. PNG compression is generally better suited for images with text and graphics, while JPEG compression is better suited for photographs, as seen in the Nikon and Canon cameras. The use of PNG compression is also compared to other formats such as WebP and BMP, developed by Google and Microsoft, which offer different trade-offs between compression ratio and image quality, as seen in the Google Chrome and Microsoft Edge web browsers. The comparison of PNG compression to other formats is also important for applications such as image processing and computer vision, as seen in the OpenCV and ImageMagick libraries developed by Intel and ImageMagick Studio LLC.

Category:Data compression