How Image File Types Work

Do you know how to select the correct file type for your image needs? PeopleImages / Getty Images

Choosing the right image file format can be crucial for optimizing both the quality and performance of a variety of projects. The path to optimization begins with a better understanding of image file types.

It certainly is true that there are lots of different image formats on the web — just at How Stuff Works, you'll find many different image formats in use at any one time, including GIF files, JPEGs, and animated images.


That's far from all of them either, either. The internet is a diverse place, that sees users lean on PNG files, TIFF files, BMP files, and a variety of Vector formats like SVG and PDF. Fortunately, it doesn't take a graduate degree from Stanford to understand the fundamentals. With that in mind, let's unpack the different image file types available and how they can be used.

A Beginner's Guide to Image Files

The term "image file" is used to describe any image-based computer file. It's a broad classification that includes all manner of formats, providing those formats are being used to store images. An image file format, or image file type, is much more specific [source: University of Michigan].

As mentioned above, denizens of the internet have leaned on a wide variety of image file formats throughout the years for a number of reasons which we'll explore in much more detail later. Before that though, it's important to introduce you to some important, image-format related concepts.


Raster Image Files

The raster image format utilizes pixels that hold color information. These types are widely used for both photographs and complex graphics. Some of the most common raster image file types include:

  • JPEG (Joint Photographic Expert Groups): offering a great balance between image quality and file size, JPEG files are commonly used for digital photography and web images.
  • PNG (Portable Network Graphics): these files are entirely lossless, and are capable of preserving the original image quality. The file sizes are larger on average, but remain a popular choice for storing web graphics.
  • GIF (Graphics Interchange Format): the GIF format has a limited color range, but is favoured for it's ability to support simple animations despite it's small file size.
  • TIFF (Tagged Image File Format): popular among professional photographers, TIFF files are high quality images that can support multiple layers and pages, and can be very large.


Vector Image Formats

The vector image files store image data differently. Instead of using pixels, vector images rely on sophisticated algorithms and coordinates. The result is an infinitely scalable file format that can be stretched out or shrunk down without compromising resolution. As you might expect, these image files are ideal for all manner of art, including font files.

The three most common image formats in use today include:


  • SVG (Scalable Vector Graphics): SVG files are ideal for web graphics that require scaling, like icons and logos, and typically stores information in XML format.
  • EPS (Encapsulated PostScript): EPS files are used for high-quality graphics in both the professional printing and publishing industries.
  • PDF (Portable Document Format): PDF files are used for documents and images that require the preservation of the original layout. Though they are universally compatible, editing them requires specialized software [Source: Mendelson].

You can see that each file format has a set of features and advantages that make it the best image file choice in a given situation. And this variety if certainly appropriate. The world uses image files in a wide variety of ways, which is why there developers have graces us with so many image formats over the years!


How Compression Affects Image Quality

One of the primary differences between the variety of image file types available is their use of compression. Compression is a method of reducing the size of a file by encoding the information more efficiently.

Lossy compression techniques, as seen in JPEG files, trade image quality for a reduced file size. Whereas lossless compression techniques, like those used by PNG and GIF files, maintain the original image quality.


Choosing the Right File Format

Selecting the right file type depends on the specific needs of a project. It's important to consider things like image quality, file size, as well as functionality.

For web use, JPEG files are ideal for photographs and realistic paintings, due to their efficient compression. PNG files are best for images that require transparency or high quality graphics [source: Moore].


For print, TIFF files remain the preferred choice for print production due to it's lossless compression, while PDF files are perfect for printable, multi-page documents like brochures and portfolios.

Whether you're developing a website, creating a printed booklet, or archiving digital artworks, selecting the right file type can be critical. But, by carefully considering the factors mentions above, you can choose the appropriate file type that balances quality, efficiency, and functionality.


Frequently Answered Questions

What is image and its types?
An image is a visual representation of an object. It can be a photograph, drawing, or painting. There are three types of images: raster, vector, and three-dimensional. Raster images are made up of pixels, or tiny dots, while vector images are made up of lines and curves. Three-dimensional images are made up of polygons, or geometric shapes.
What are the 2 types of image?
There are two types of images: raster images and vector images. Raster images are created with pixel-based programs or captured with a camera or scanner. Vector images are created with vector-based programs.