Lab

Drawing Software

Most of us have some kind of image-editing software, such as Paint Shop Pro, for manipulating and touching up digital photos, and it can be tempting to use this for every kind of artwork you want to produce on your PC. But you shouldn't. Paint Shop Pro is not the best program for knocking up business charts, technical diagrams and most kinds of illustration that start from a blank canvas. For projects such as these, you need a vector drawing program.

A digital image such as a photo consists of a grid containing a certain number of pixels, which means it has a fixed resolution. The larger you display or print it, the larger each pixel becomes and the more likely you are to see the pixels instead of the picture. If you draw a perfect circle in your image editor, zoom in and look at the edge, you'll see that it's not perfect at all.

Vector graphics are different. A circle in a vector program really is a perfect circle, mathematically defined. You can zoom in as much as you like or print it as large as possible, and it will stay smooth. This is because it is 'resolution independent'. What's more, as the circle is stored as a discrete object, you can move it around the screen independently of other shapes that overlap it.

You can create images using vector shapes as elements, giving each an outline and a fill. This method is ideal for creating flowcharts, organisational charts and schematic diagrams because you can easily duplicate items, edit them and move them around. Alternatively, you can combine shapes more creatively to build up a picture. To illustrate a face, for example, you wouldn't draw a face shape, an eye shape and so on. Instead, you would draw shapes for each area of the face according to its shading: a large dark shape for a patch of shadow, for example, and a small light shape for a highlight. For subtle shading, you can 'blend' one shape into another. So after placing a small, pale shape on top of a larger, mid-toned shape to create a highlight, you would blend these two shapes. The result is a series of intermediate shapes progressing from one to the other to produce a smooth transition.

Professional illustrators laboriously create hundreds of blends to shade a drawing, but for the rest of us there are plenty of short cuts. Gradient fills create smooth colour transitions in a single shape: for example, a circle with a radial gradient fill, going from light at the centre to dark at the edge, will look like a ball. Mesh fills, which are available in an increasing number of programs, let you place several colour points in one shape and blend between them automatically. Outlines, also called strokes, can be enhanced with brush effects.

For creative graphics, you can distort shapes, perhaps roughening an outline or bending a piece of text into a fancy shape. The current generation of drawing software can even apply the kinds of effects you'd associate with image editors, such as feathered edges, glows and shadows. To achieve this, sections of the artwork are converted to a bitmap image, or 'rasterised'. This happens automatically, but you need to remember that raster effects are not resolution-independent, so it's important to set the right rendering resolution for your document before you export or print it.

There are many vector-based programs specifically for computer-aided design (CAD) tasks such as engineering and architectural drawing. Another category of vector software, which includes programs such as Microsoft Visio, SmartDraw and ConceptDraw, specialises in business diagrams. In this review we're concentrating on general-purpose drawing programs aimed at graphic designers and any user whose primary aim is an attractive end result. However, some borrow features from the other types of drawing program, such as dimensioning lines, for showing measurements on plans, and smart connector lines that link objects in flow diagrams and the like and reroute themselves when the connected shapes are moved.