Figures

The preparation of figures for scientific books can be an awkward process, since so much of the responsibility is placed on the author. Having figures drawn professionally is very costly, and can prevent a book from being commercially viable; hence the usual request that the illustrations be produced by the author. This page provides some basic guidelines to help you when drawing your figures. We will assume, throughout, that you are creating the illustrations electronically, not drawing them by hand on paper.

Types of figure

For the purposes of printing, there are two basic types of figure:

• Line drawings
• Halftones (typically photographs and computer screenshots)

Both types can be either monochrome or colour.

Line drawings

Word processors provide simple tools for producing line drawings. Use these only as a last resort! Such drawings can’t be imported directly by typesetting software, so they have to be converted to another format: a complicated and imperfect process. Instead, use a drawing tool such as Adobe Illustrator, Corel Draw or Visio. Most typesetters can work with files produced by this kind of package.

You may be asked to produce figures in Encapsulated PostScript (EPS) format. PostScript is the language of professional publishing, so EPS is a good format to use. If your publisher asks for EPS files, discuss the details of this with them, as there are a number of pitfalls.

Halftones

Photographs

If your photographs exist as glossy prints, supply the prints to the publisher. Although the prints will be scanned to produce electronic files, there is no benefit to you in trying to do the scanning yourself.

If your photographs have already been scanned, or come from a digital camera, supply them as they are. Don’t be tempted to do any processing of the digital images yourself. You may find that some images produce very large files, so either supply them on CD-ROM or compress them using a utility such as WinZip.

Screenshots

Since screenshots are taken directly from a computer’s display, they should, in principle be perfect and require no additional processing. Unfortunately, even the act of saving the files can cause problems, as discussed in the next section.

File formats

Halftones are saved as bitmap images, of which there are many formats. Common ones include BMP, GIF, PNG, TIFF and JPEG. Of these, the first four are lossless formats, preserving all of the information in the image, while JPEG is a lossy format, which throws away a certain amount of detail in order to compress the file to a very small size. It is tempting to save a large scanned image or a screenshot in JPEG format to save disk space, but this can lead to an unacceptable loss of quality. The examples below should make this clear.

JPEG and screenshots

JPEG compression can introduce unacceptable artefacts into a screenshot:

Consequently, you should never save a screenshot (or any images with large flat areas of colour) in JPEG format. Use TIFF or BMP; GIF is also possible, but only allows 256 colours, so you can lose quality when converting from images with more colours.

JPEG and photographs

Digital cameras usually save pictures in JPEG format, and this is fine for first-generation images. The complexity of the image hides the artefacts from the human eye, and the picture should be acceptable for printing. However, if you want to edit the image you should save it in a lossless format first. The reason is that repeated application of the JPEG compression algorithm, which happens every time you save a JPEG file, progressively degrades the image. The example below shows what happens if you save a JPEG file 10 times, making no other changes to the file. (These images are double their original size, so that you can see the effect more clearly.)

In other words, if you make any changes to the file, save it as a TIFF or BMP file to avoid this kind of problem.

Colour

Most technical books don’t use colour (although there might be a colour plate section). Consequently, unless your publisher tells you otherwise, you should prepare line drawings in black and white (with shades of grey, if necessary). Halftone images are best supplied in colour, regardless of whether or not they will be printed in colour. This gives the illustrator maximum freedom to produce the best quality output.

Size

Line drawings

Preparing your figures at the right size will help a lot. Find out, from your publisher, the maximum width that a figure can occupy on a page, and draw your figures to fit this. If a figure can’t be made to fit within this width, then it can be rotated 90° to fit between the top and bottom margins of the page, but try to avoid this if you can.

For a consistent look throughout the book, use the same typeface and type size in every figure. A good tip is to decide on the type size first (8 pt or 9 pt type is common) and then start drawing each figure by typing a small amount of text in the right size. Then size all your boxes and arrows to fit (remembering also to stay within the maximum overall width of the figure).

As well as making the type a consistent size, make all the lines used in the drawing a consistent width. As a guide, lines should normally be 0.5 pt wide; thick lines can be 1 pt wide.

Halftones

Halftones are always printed at a resolution of 300 dots per inch. Therefore, for good quality reproduction of a figure x inches wide by y inches high your figures should be x × 300 pixels wide and y × 300 pixels high. It doesn’t matter if they are of higher resolution, but if you supply an image that is only 100 pixels × 100 pixels, for example, no one will be able to make it look good.