A file format corresponds to a specific encoding standard established for storing information on a computer – it defines how bits are used to store data types. Each file format corresponds to a different standard that can vary greatly in complexity, depending on the content of the stored information. The contents are usually classified into the main and distinct groups: images, audio, video, and text – although the growing demand for new applications has led to the addition of more format structures.
There are proprietary or closed formats as opposed to free or open formats. Open formats are specified and maintained by an established organization and can be used on any system, by any person, and for any purpose, such as the JPG format, which can be edited on any operating system (Windows, MAC OS, Linux, Android, etc.) using any image application, whether free, proprietary, or open source. Closed formats are considered trade secrets, involving special encoding standards developed by the organizations that own them, implying specific software for their use, such as the PSD image format which can only be edited in its original program or package (Photoshop – Adobe suite), although among proprietary programs there is often the possibility of importing formats from other proprietary programs, but not between free and open source programs.
The file format is identified by its extension, which corresponds to the abbreviation shown after the period that separates it from the name assigned by the user: FileName.extension
The file formats covered in this guide are free formats and belong to the image group, subdivided into two types – bitmaps and vectors.
Bitmap Open File Formats
JPG or JPEG – a format developed by the Joint Photographic Experts Group as a standard for storing large images in smaller files, permanently compressing image sectors into pixel blocks, with compression ratios ranging from 2:1 to 100:1, depending on the settings. Ideal for photography in general, but not recommended for images involving flat colors such as illustrations, line art, or typography. Images saved in JPG format also lose quality each time they are edited and saved.
PNG – Portable Network Graphic format using indexed color methods (page 300) and lossless compression, similar to a GIF file, but without copyright limitations and with the possibility of blending opacity with transparency, since PNG includes an 8-bit channel that allows the gradation of opaque tones to transparencies. Ideal for web use and direct color printing. This format does not support CMYK profiles, therefore it is not suitable for four-color printing.
GIF – Graphics Interchange Format using indexed color methods and, like PNG and unlike JPG, also uses lossless compression. Originally developed by CompuServe Inc. in the early 1990s, the format includes some important features such as compression, transparency, interlacing, and storage of multiple images in a single file, which allows for a basic way to generate small animations. However, GIF drastically lost popularity due to copyright issues that led to the creation and development of the PNG format as an alternative. The copyrights involved expired in 2004, but the PNG format had already gained ground over GIF. PNG does not allow for animation, but it has the advantage of enabling gradation in transparency, as mentioned above. GIF is only appropriate for the web environment (internet).
TIFF or TIF – Tagged Image File Format using true-color and deep-color methods (page 301), very popular in the graphic, editorial, and photographic fields. Created in the 1980s for use in electronic publishing (page layout, editorial area), the great advantage of TIFF is the ability to maintain quality every time the image is edited and rewritten, making this format somewhat larger than JPG and therefore ideal for editing, storage, but also for high-resolution printing.
Webp – a next-generation raster or bitmap graphics format, developed by Google LLC, with the aim of replacing JPEG, PNG, and GIF formats. It supports lossy and lossless compression, as well as animation and alpha transparency, specifically created for web applications.
Avif – successor format to Webp, developed by the Alliance for Open Media, based on the Av1 video format, which shows better compression efficiency than any of the previous formats, as well as better preservation of details, less color loss on hard edges of images, text and graphics, and specifically created for web applications.
Open Vector File Formats
EPS – Encapsulated PostScript format structured in accordance with a set of standards for PostScript, which in turn corresponds to a programming language that describes the appearance of the printed image. This is a completely different method from bitmap formats, created by Adobe in the 80s, capable of describing images, vectors and text in the same document. Ideal for the graphic arts industry.
SVG – Scalable Vector Graphics format structured on an XML (Extensible Markup Language) basis, a markup language that establishes the rules for encoding documents in a doubly readable format – human and machine. This format describes two-dimensional vector graphics with support for interactivity and animation. Having been created by the W3C in the late 90s, this format was specifically created for web application.
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