At some point, all of us have laughed at a hilarious animated GIF or shared a beautiful JPEG photo. These are just a couple of examples of raster file types. Everyone who uses a laptop, tablet, cellphone or digital camera will come into contact with raster graphics on a daily basis—but how much do you really know about them? This article and infographic will give you a handy rundown of some of the most common raster file types, their pros and cons, and their specific uses.
Table of Contents
Common features of raster images
Whilst all raster image formats are different, there are a few basic features which all of them share.
Raster graphics are one of the two most common methods used to display images, and can be contrasted with vector graphics. When you take a photo with a digital camera, scan an image using your scanner, or view most computer graphics, then you’re dealing with raster graphics.
A raster image is essentially a rectangular grid. Within this grid lie thousands of tiny individual squares of color, known as pixels. Together, these pixels form the image that you see on screen. However, each pixel acts independently from all the pixels around it. So, when you zoom into a raster image, you’re not making the image bigger—you’re actually making each individual pixel within the image bigger. As a result, zooming into or scaling a raster image can leave it looking blurry and undefined. Raster images are only intended to be viewed at a particular size, and lose quality when scaled up or down. This is known as resolution dependency.
Overall evaluation of raster images
Raster images faithfully display the color information of an image, making them a great choice to display detailed images
They’re widely supported by web browsers, which makes them easy to share
They can be opened using practically any image editing software
Scaling a raster image can dramatically affect its quality
There is no way to pick out and edit an individual element within a raster image—any changes you make will affect the image as a whole
Uncompressed raster images are large in file size—and even when compressed, they’re often still larger than equivalent vector graphics
Their detail can make them an unsuitable choice for certain applications, such as for logos
Raster File Types
The JPEG format is named for the organization which created it, the Joint Photographics Expert Group. This is an extremely common format, and is typically used for sharing photographs. Its small size means that digital cameras are able to store large numbers of photos with a small amount of memory.
JPEG uses 24-bit color depth, which means that a JPEG image can contain more than 16 million colors!
Since JPEGs are typically small in size, they take up little memory on a PC or digital camera, and can easily be shared via email.
JPEGs are widely supported by web browsers.
Unlike GIF, JPEG only supports still images—no support for animation
JPEG images are compressed with lossy compression, which means they lose quality when edited
The format doesn’t support transparency.
JPEG 2000 was created to improve upon the existing JPEG format. Whilst the original JPEG format caused images to lose quality when compressed, JPEG 2000 was designed to combat some of this loss in quality. It uses a wavelet-based method to compress images, with the goal of storing higher quality images within a small file size. Despite these advances, JPEG 2000 has not become a widely-used format.
JPEG 2000 improves upon JPEG by reducing the perceptibility of compression artifacts
It supports both lossy and lossless compression
More flexible file format
Despite its advantages over JPEG, it has remained an uncommon format
It is not widely supported by web browsers
In certain cases, JPEG 2000 can still be less efficient than other formats, such as PNG
One of the most common image formats on the web, GIFs (Graphics Interface Format) are typically used for web graphics. Unlike many other formats, GIF also supports animated images. The popularity of animated GIFs is such that GIF has become one of the most widely-recognized file formats around—and for many people, “GIF” is synonymous with “animated GIF”. To learn about GIF to DXF conversion, click here.
Its support for animation has made it incredibly popular
It is widely supported by web browsers
Uses lossless compression
A GIF file can store only 256 colors
Despite their lossless compression, GIFs are often of low resolution
In most cases, GIFs have larger file sizes than equivalent JPEG or PNG files
PNG is the most used lossless image format on the internet. The format was created to improve upon the existing GIF format. There were clear deficiencies with GIF, but as it was patented, there was no way for external programmers to improve upon it. The idea thus came about for a replacement format: PING, to stand for PNG Is Not GIF. At the time, only 3-letter file extensions were available, so PING became PNG. Nowadays, PNG officially stands for Portable Network Graphics.
PNG supports different color depths, from 8-bit color (256 colors) through to “true color” (24 bits, over 16m colors)
Uses lossless compression
Uses more advanced transparency than GIF
Supported by current web browsers
Better format for high-quality images than JPEG or GIF
Not supported by some older browsers (such as IE6)
The higher quality results in larger file sizes
Bitmap is one of the simplest file formats in raster graphics. Whilst other raster formats are more complex, a bitmap (or BMP) file simply contains information about each individual pixel in the file. In the past, BMP files were uncompressed, leading to huge file sizes. Now, it’s possible to compress BMP files using lossless compression, though uncompressed bitmaps are still available.
Because of its simplicity, virtually every device imaginable supports BMP files. However, its huge file size means that in most circumstances, BMP is one to avoid. If, however, you still need to convert using this file format, find out more about how to use Scan2CAD to convert BMP to DXF.
BMP supports true color images (24-bit color depth, more than 16m colors)
Lossless compression is now available for BMP files
Supported by practically every device
BMP files are typically very large in size
Usually do not scale well
TIFF (or TIF) is a commonly-used file format in the fields of printing, graphic design, and photography. TIFF stands for Tagged Image File Format, as TIFF files also include tags containing additional information about the image. It uses lossless compression, and is useful for storing high-quality images.
Due to its high quality, it is a good file format to choose if you want to vectorize your raster image. In fact, Scan2CAD recommends saving your image files as TIFF before converting to DWG or DXF in order to increase your chances of optimal vectorization results.
TIFF supports high-quality images
Uses lossless compression
Supports true-color images
Recommended for vectorization
Not widely supported by web browsers
Some programs are unable to open compressed TIFF files
Typically very large in file size—a single TIFF file can take up 100 MB of storage space
Often too large to send via email
One of the first widely accepted image formats, PCX (Picture Exchange) was created in 1985 to serve as the native file format of the PC Paintbrush software. In the proceeding decades, however, newer formats (such as JPEG, PNG, and GIF) have superseded PCX, and it is no longer a common format.
Good image quality
Extended to support true color images
Older versions only support 8-bit color depth
File sizes can be large
Surpassed by more modern formats
Which raster file type should I use?
With so many file types available, it can be difficult to know what to choose—especially since each file type fulfils a similar purpose. However, there are subtle (and less subtle) differences between the formats which mean that each of them has specific uses. JPEGs, for example, are a great format for storing and sharing photos. The lossless nature of PNG images makes them a good choice for web graphics. GIF, meanwhile, is a perfect choice for sharing animated images.
If you’re here on the Scan2CAD blog, though, you’re probably interested in knowing which format is the best to choose for converting from raster to vector. We recommend saving your raster images in TIFF format due to their lossless compression and support for high-quality, true color images. Their file size may be a concern for certain applications, but for vectorization purposes, the good image quality offered by TIFF is crucial.
Whilst this list covers some of the most commonly-used raster formats, it is not exhaustive. There are hundreds of different file types available—check out which raster (and vector) file types are supported by Scan2CAD.