Graphics for Scientists - Part 3 - Raster File Formats

This is part of a series of posts about producing publication quality graphics. See here for the introduction and links to other parts.

In parts one and two I introduced the main categories of image formats and some other basic concepts. Here I’ll run through the most common raster ones and some advantages/disadvantages.

Raster Formats

TIFF (.tif/.tiff)

Tagged Image File Format (TIFF) is the “publication/print quality” raster format that you are most likely to come across. It’s advanced format with some useful features including layers, transparency (aka alpha channels) and the ability to contain some vector information. This has made it the industry standard for raster images but there are some pitfalls that you need to avoid.

Advantages

• widely accepted industry standard
• can contain multiple layers, transparency, and vector components
• support for lossless compression

Disadvantages

• large size unless compressed
• support for lossy compression including JPEG
• poorly supported by software except specialist graphics programs

PNG (.png)

Portable Network Graphics (PNG) is another common raster format that is being increasingly accepted by publishers.

Advantages

• often accepted for publication
• lossless compression is standard
• supports transparency
• widely read by non-specialist software (e.g. web browsers)
• small file sizes

Disadvantages

• no layer support

JPEG (.jpg/.jpeg)

JPEG is the most common digital image format and is usually not accepted by publishers (in my experience).

Advantages

• easily read on by a very wide range of software/devices

Disadvantages

• rarely accepted by publishers
• lossy compression that can be varied in quality and can lead to very nasty artefacts

GIF (.gif)

Graphics Interchange Format is commonly used for web-based graphics due to their small file sizes (a hangover from the days of 56 kbps modems). They are very limited apart from the ability to do animation.

Advantages

• you can make animations like this

Disadvantages

• not accepted by publishers
• limited to 256 colors
• lossy compression
• everytime you use a gif for print publishing a graphic designer crys
• editors will assume you previously published you paper on geocities

Bitmap (.bmp)

If you’ve used old (pre-Windows 95) version of Microsoft Paint you’ll be familiar with bitmap graphics files. There’s nothing really wrong with them but the files sizes are large unless you use compression. May as well use a TIFF.