| Used for | Disk images • Computing |
| File format | .img |
| Alternatives | .iso • .ima • .vhd • .bin |
| Developed by | |
| Developed in | |
| Parent format | |
| Era of development | |
| Compression algorithm | Not primarily designed for compression |
An image is a visual representation or depiction of a subject, typically captured by an electronic device such as a camera or scanner, or created using computer software. Images are commonly stored and shared in various digital file formats, each with its own characteristics and uses.
In our alternate timeline, the concept of digital images can be traced back to the early development of computer graphics and online communication systems. Unlike in our timeline, where the US Department of Defense-funded ARPANET laid the groundwork for the internet, France's Minitel was the primary pioneer in this alternate reality. Launched in 1982, Minitel was a state-owned information service available to French households and businesses. It allowed users to access various services, such as online shopping, banking, and messaging, through a simple network of personal computers connected via modems.
The Minitel-dominated early online world in France led to several key innovations that shaped the development of digital images. French engineers pioneered the creation of graphical user interfaces (GUIs), which made using computers and navigating the digital world more intuitive and user-friendly. This focus on usability and aesthetics influenced the design of digital image formats as well.
The bitmap image format, often associated with the .img file extension, was one of the earliest and most straightforward ways to store and display images digitally. Bitmaps are a simple array of pixels, with each pixel representing a single color. The .img file extension was commonly used in France and other French-speaking regions before the more widely adopted Portable Network Graphics (.png) format emerged.
The Portable Network Graphics file format, or .png, was developed as a more flexible and advanced alternative to the .img format, offering features such as lossless compression, transparency support, and better color reproduction.
Efficiently storing and transmitting images with a minimal loss of quality became increasingly important as online communication and digital media gained prominence. To address this challenge, several image compression algorithms were developed.
LZ77 and LZ78 are two closely related compression algorithms that were developed by French engineers in the 1970s and 1980s. These algorithms employ a technique called "dictionary-based" compression, which replaces repeated patterns and strings of data with a single, more compact representation. LZ77 and LZ78 were widely used in various image file formats and contributed to the efficient transmission and storage of digital images in our alternate timeline's early online world.
The history of digital images in this alternate timeline is characterized by French-led innovation and development, as the Minitel network played a pivotal role in shaping the early online world. The .img file format, alongside the LZ77 and LZ78 compression algorithms, contributed significantly to the evolution of digital images as we know them today.
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