Image files are among the most ubiquitous digital file types in the world of personal computing and in several lines of business, like marketing, web development, advertising, graphic design, etc. This article explains the 12 types of image file formats in use today. It also discusses the key features of image files and how they work.
Defining Features of Image Files
Image files are probably the most commonly encountered file type by regular computer device users. At the beginning of the digital learning curve, users experience image files in various formats used in different scenarios – from social media to photography and personal sharing. In recent years, image files have become all the more critical for two reasons:
- The rise of platforms like Instagram and Pinterest: Platforms such as these rely heavily on images (and other types of visuals) to garner traffic. Related to this is the rise of digital ads, which also use embedded images to attract users.
- The software as a service (SaaS) and web app revolution: With many personal and productivity applications moving online, image files are everywhere. Productivity apps rely heavily on file types like icons to interact with the user and improve the user experience (UX).
However, despite their ubiquity, image files are more complex than they may seem on the surface. Digital images have been around for several decades, and image file types have evolved over the years to keep up with emerging trends. For example, since 2021-2022, we have seen the widespread use of 3D file types that can capture and represent a sense of depth through a three-camera setup and appropriate encoding of the file’s information.
The first digital images appeared in the 1960s, driven by advancements in satellite imagery, aerospace research, and medicine. At that time, these digital images were still not linked with computing, and it would be many years before personal computing became widespread.
Only in the 80s and 90s did software applications like Deluxe Paint and PC Paintbrush start being shipped with computing devices. Thanks to these applications, users could now create and save their own images to personal computer storage. This gave rise to the first generation of image file types, as we know them today, outside of industrial use.
Deluxe Paint used the Interchange File Format (.iff) image file extension, while PC Paintbrush used the PiCture eXchange (.pcx) format. Both of these are defunct today. In its place, the 90s saw the rise of Joint Photographic Experts Group (.jpeg) and Bitmap (.bmp) formats that would stand the test of time and are still being used today.
Apart from this, several image editing software applications have their own native file extensions, which have evolved to keep pace with the software. For example, .stl, .obj, etc., have been developed to contain and convey 3D printing information in 3D files, distinct from image files.
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Now that we have looked at the meaning of image files let us discuss their defining features:
1. Contains encoded information
A digital image, like any other file, encodes information found in the real world into a format that machines can understand. For an image, this is typically done by setting multiple thresholds for different levels of darkness and then marking pixels darker or lighter than that threshold with 1 or 0. More complex algorithms are developed for more complex image types using data processing tools like MATLAB.
A digital image can not only store information, but it can also convey it. This means that output devices can read image file types and present them to the user in a visual format. If you use the correct software application, it is also possible to edit the contents of an image file already created.
2. Includes a header and image data
All image file formats have two parts – the header and the data. The header contains essential metadata about the file, such as its format, compression type, whether it is a grayscale or color image, the image’s dimensions, version and editing information, etc. Notably, the length of the file header is often fixed so that it does not contain anything more than strictly necessary data. Inside, the image data will contain the encoded version of the visual representation. It may also include a color map that aligns pixel-level data with a range of colors.
3. Follows a raster or vector format
Raster formats are the regular 2d digital images that we see every day. They are widely used to edit images and photos in graphic design. Raster files are made of pixels, while vector image files are composed of paths. As a result, vectors have several parts that together form clear outlines of shapes. These paths are independent of resolution. On the other hand, Raster files are an array of pixels that form a complex image.
4. Can be resized with or without a loss in quality
A defining feature of an image file is that it can be resized – i.e., shrunk or expanded while maintaining the ratio of its dimensions. A lossless compression algorithm archives this while preserving the quality, but it may add to the file’s size. In regular (lossy) compression, the image file is expanded, but there can be a near-imperceptible loss in its quality.
The image file type you choose will depend on the application, the use cases, and the resources available (e.g., memory).
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12 Types of Image File Extensions
The 12 key image file types and their extensions that are widely used today are detailed below in alphabetical order:
1. Adobe Illustrator (AI)
Overview: AI file is a proprietary Adobe Illustrator (AI) format for vector images developed by Adobe systems. AI files are small in size and easily scalable. Vector files are built on an infinitely expandable and complex graph-like formula; thus, they don’t lose resolution when scaled. They also allow for layering and transparency. The filename extension is .ai.
Best suited for: AI files are used mainly by designers and illustrators in print media and digital graphics. AI files are only compatible with Adobe Illustrator or other professional editing software, albeit with fewer capabilities.
Pros: AI files offer infinite resizing capabilities. This makes them an excellent choice for reproducing print illustrator drawings and logos.
Cons: AI file formats are not supported by browsers nor by most default image viewers and are not meant for use on the web.
2. Bitmap (BMP)
Overview: Bitmap (BMP) files were initially developed to display high-quality images on Windows computers, although they are currently compatible with Mac and Android devices as well. BMP files store two-dimensional images in monochrome or color. The filename extensions are .bmp or .dib.
Best suited for: BMP files are compatible with most web browsers, standard image viewers, and editing software. Designers and photographers use BMP files to store and print high-quality digital photos.
Pros: BMP files are device independent and thus can be stored across multiple devices without loss in quality. They can also handle multiple color depths, profiles, and alpha channels.
Cons: BMP files only contain red, green, and blue (RGB) images, which is unsuitable for people who regularly use cyan, magenta, yellow, and black (CMYK). Uncompressed BMP files are unsuitable for sharing, use on websites, or storing.
3. Encapsulated postscript (EPS)
Overview: An encapsulated postscript (EPS) file is a vector image used for storing illustrations in Adobe Illustrator or third-party illustrators such as CorelDraw. EPS files support lossless scaling as text-based documents outline shapes and lines using code. The file name extensions are .eps, .epsf, and .epsi.
Best suited for: EPS extension is a universal file type that can open vector-based artwork in any design editor. Designers and artists use EPS files to produce high-resolution graphics for print. EPS files create logos, vector artwork, illustrations, and icons.
Pros: EPS image files are backward compatible with printers and thus suitable for printing with a wide range of printers.
Cons: EPS files are not supported by major web browsers. They are also not editable once saved, requiring designers to use the original design file to make changes before resaving.
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4. Graphics interchange format (GIF)
Overview: GIF stands for graphics interchange format. It is a raster format that uses lossless compression. However, it restricts the image to 8 bits per pixel and can contain only 256 indexed colors; thus, it has lower quality. GIF files are popular for animating support used in memes or creating animated banners. The filename extension is .gif.
Best suited for: GIF files are compatible with web browsers and several image viewers. Content creators use GIF files to create how-to tutorial guides.
Pros: GIF files offer animation support by allowing images or frames to be combined. The file sizes are small and load faster on web pages.
Cons: GIF files are limited to a palette of 256 colors; thus, images have low resolution and, at times, maybe blurry. Editing GIF files can be time-consuming because they combine multiple images.
5. High-efficiency image file (HEIF)
Overview: HEIF stands for high-efficiency image file format. It is an alternative to JPEG with almost twice its efficiency. HEIF is a lossy compressed format that requires less storage space while maintaining the same image quality. The filename extensions are .heif(s), .heic(s), .avci, and .avif(s).
Best suited for: HEIF files are associated with Apple devices. Major browsers do not support HEIF files. Professional photographers use HEIF files as they have high image quality with a 16-bit color scheme.
Pros: HEIF files can contain image sequences, storing multiple images in a single format, such as burst images or live photos.
Cons: HEIF is a raster image format which leads to a loss of quality when scaling up images. Most social platforms do not offer support for HEIF files; therefore, uploaded images lose their quality.
6. Joint photographic experts’ group (JPEG or JPG)
Overview: The joint photographic experts’ group (JPEG or JPG) file format is the most common file type found across the web and in photographs. JPEG files use lossy compression to compress images for storage and sharing. They also support up to 24-bit color. The filename extensions are .jpg, .jpeg, .jpe, .jif, .jfif, and .jfi.
Best suited for: JPEG files are supported by all browsers and image viewers. Photographers use them to display photographs as they are small. Bloggers also use JPEG files to display images for faster page loading times.
Pros: JPEG image files allow for easier post-processing as white balance and saturation are set with the shutter’s click.
Cons: Lossy compression of JPEG files may cause the appearance of artifacts such as noise, blooming, and aliasing on the edges of images, thus affecting image quality.
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7. Portable network graphics (PNG)
Overview: Portable network graphics (PNG) is a raster file format that supports lossless data compression. PNG files are suitable for displaying high-quality digital images on web pages as they allow saving images with a greater color variation on a transparent background. The filename extension is .png.
Best suited for: PNG files are supported by all major browsers, software, and image editors. Designers use PNG files for logos as they support transparent backgrounds. They are also used to display detailed graphics and charts on websites.
Pros: PNG files have greater color variation than GIF files and thus can store more detailed images.
Cons: PNG files retain original data when compressed and thus are bigger when compared to GIF or JPEG files. They are also unsuitable for print media as they don’t support cyan, magenta, yellow, and black (CMYK) color modes.
8. Adobe Photoshop (PSD)
Overview: PSD is an image file format used for saving image documents and works in progress in Adobe Photoshop. PSD files contain an image with layers and masks. The layers are stacked on top of one another, allowing designers to credit images using multiple levels of transparency. The filename extension is .psd.
Best suited for: PSD files are compatible with browser-based apps and professional editing software such as Photoshop, Adobe Illustrator, and Premiere Pro. Designers and artists use PSD files to produce and edit high-quality images.
Pros: PSD files support high-quality graphics with a vast image depth and color depth range, as they can retain up to 30,000 pixels in height and width.
Cons: After manipulation, PSD files may get large, up to 2GB making it impractical to share or store. PSD files are also not meant for use on the web.
9. Raw or camera uncompressed format
Overview: Digital cameras use raw image file formats to store full-quality and unedited images. Raw files can be large as they contain uncompressed images. Raw files can have up to 14-bit color per image, which gives photographers flexibility when editing in post-processing. Raw has several filename extensions, such as .3fr, .arw, .cr, and .rw2.
Best suited for: Raw files are compatible with major browsers and can only be edited in relevant software such as Photoshop or Lightroom. Photographers edit and convert raw files before printing.
Pros: Raw files are uncompressed and detailed; thus, designers have more to work with. They have a wide color range and increased RGB tonal values.
Cons: Raw files are large, which may require additional space. They are also not suitable for web use.
10. Scalable vector graphics (SVG)
Overview: Scalable vector graphics (SVG) is an extensible markup language (XML) vector image format for two-dimensional graphics with support for animation and interactivity. The SVG file format is commonly used in responsive web design as it stores text information in a discoverable form by search engines. The filename extensions are .svg and .svgz.
Best suited for: SVG files are supported by major browsers and most illustration software. Designers can resize SVG files with no loss in quality; thus, these files display icons, logos, and simple illustrations.
Pros: SVG files describe images and graphs in a form that is readable by search engines. Therefore, they are used for SEO optimization.
Cons: The code in SVG files is difficult to understand for beginners. They cannot display high-quality images as they lack pixels.
11. Tag image file format (TIFF)
Overview: TIFF stands for tag image file format. TIFF is a raster image format commonly used for storing and editing photos, graphics, and artwork for print. TIFF supports both lossy and lossless compression. They are usually uncompressed and large. TIFF files also support transparency. The filename extensions are .tiff and .tif.
Best suited for: TIFF files are compatible with software such as Adobe Illustrator and Photoshop. They have limited browser support, such as Safari and Edge. Professional photographers and editors use them to produce and store high-quality photos before printing.
Pros: TIFF files work as containers for smaller JPEG files and can store multiple images in a single raster graphic.
Cons: TIFF formats are not suitable for use on the web. TIFF files are large due to incredible details and resolution and thus can be impractical for storing or sharing.
12. Web picture (WebP)
Overview: WebP format enables developers to create smaller images of the same quality as JPEG files. The web file format supports both lossless and lossy compression for digital images. WebP formats also provide support for animation and transparency. The filename extension is .webp.
Best suited for: WebP is compatible with major web browsers and professional image editors such as Photoshop. Web developers and designers use WebP files and animated WebP files to compress photos and graphics without reducing the quality of the website images.
Pros: WebP files come in small sizes, which enable faster web loading speeds and enhance user experience. They also save server disk space for websites.
Cons: WebP files require a good internet connection. Sometimes, compressions can lead to reduced quality of images.
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Takeaway
Image files are a fundamental piece of technology in the modern world. They aid in information sharing, and depending on the file type you choose, they can increase the user’s productivity in different software applications. The 12 image file types discussed in this article are the most notable ones, but there can be several more if you use a wide range of photo editing and visual design tools. The correct image file type will optimize memory usage without compromising quality and reusability.
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