Motifs and Patterns on the Computer
Senior 3 · Fine Arts
Motifs and Patterns on the Computer
Lesson 2 of 4
25 min
Open a photograph on a phone and zoom in as far as it will go. Sooner or later the picture turns into small coloured squares. Now zoom in on the logo of a bank or a mobile network on its website: it usually stays crisp however far you go. The two images are stored in completely different ways. Choosing the right kind of image, and the right program, is the first decision in digital design.
Definition
Pixel: one tiny square of colour; a digital photograph is a grid of millions of them.
Raster image (bitmap): an image stored as a grid of pixels. Examples: photographs, PNG and JPG files.
Vector graphic: an image stored as shapes described by mathematics (points, lines and curves), which the computer redraws at any size. Examples: logos, SVG and PDF files.
Path: a line or outline in a vector graphic; node: a point on a path that you can move; handle: a control that sets how a curve bends at a node.
Fill: the colour inside a shape. Stroke: the colour and width of its outline.
Resolution: how many pixels are packed into each inch of a print, written ppi or dpi (dots per inch).
| Raster | Vector | |
|---|---|---|
| Made of | a grid of pixels | paths with nodes, fills and strokes |
| When enlarged | turns blocky or blurred | stays sharp at any size |
| Best for | photographs, digital painting, textures | motifs, patterns, logos, lettering, posters |
| Free programs | GIMP, Krita | Inkscape, LibreOffice Draw |
| File formats | PNG, JPG | SVG, PDF |
Motifs and patterns should be made as vectors. A pattern repeats one motif many times, so every copy must be exactly the same and every edge must meet cleanly. The same design may end up on a phone case 8 cm wide or a hotel wall 3 m wide, and a vector file will print sharply at both sizes. You can also recolour the whole design in seconds.
The examples in this unit use Inkscape, a free and open-source vector program for Windows, macOS and Linux (inkscape.org). LibreOffice Draw, often installed on school computers, has similar tools. The names of menus differ between programs, but the ideas are the same.
You choose a tool in the toolbox (3), adjust it in the tool controls bar (2) and work on the page (4). The Fill and Stroke panel (5) sets exact colours, and clicking a palette swatch (6) colours the selected shape quickly. Always read the status bar (7): it tells you what is selected and what the tool will do next.
| Tool or command | What it does | Inkscape shortcut |
|---|---|---|
| Selector | select, move, scale; click again to rotate | S |
| Node tool | move nodes and handles to reshape a path | N |
| Rectangle, Ellipse, Star and polygon | draw basic shapes; hold Ctrl for squares, circles and fixed angles | R, E, * |
| Pen (Bézier) | draw straight and curved paths node by node | B |
| Duplicate | make an exact copy in the same place | Ctrl+D |
| Flip horizontal, flip vertical | mirror the selection | H, V |
| Group, ungroup | treat several shapes as one | Ctrl+G, Shift+Ctrl+G |
| Align and Distribute | line shapes up and space them evenly | Shift+Ctrl+A |
| Fill and Stroke | set exact colours and outline widths | Shift+Ctrl+F |
| Show grid | turn the page grid on or off | # |
You have just made the lozenge tile from Lesson 1, Figure 1. In Lesson 3 you will design a motif of your own.
Keep working in SVG, which keeps every path editable. When a design is finished, export a copy as PNG for screens or printing. For print, choose 300 dpi; for a screen, 96 dpi is enough. Save often, and keep each version with a number (tile01, tile02) so you can go back.
Worked example 1: how many pixels for a print?
Kamanzi will export a pattern tile and print it 20 cm wide at 300 dpi. How many pixels wide must the PNG be?
Step 1. Convert to inches (1 inch = 2.54 cm): inches.
Step 2. Multiply by the resolution: pixels.
Answer. About 2362 pixels wide. Because the design is a vector, Inkscape can export it at this size with no loss; a small raster photo stretched to this size would look blurred.
Worked example 2: choosing the right kind of file
For each job, choose raster or vector. (a) Retouching a photograph of a basket. (b) A motif that will be printed on T-shirts and on a banner. (c) A school logo.
(a) Raster: a photograph is already pixels. (b) Vector: one file must print sharply at two very different sizes. (c) Vector: a logo is used everywhere, from letterheads to signboards, and must stay crisp.
<em>Inkscape Explained in 5 Minutes</em>, from the Logos By Nick channel. Watch for the toolbox, the Fill and Stroke panel and how shapes are combined; then try the same steps on your own computer.
Warning
Don't design in a raster program by mistake. A pattern drawn in a photo editor cannot be enlarged cleanly later.
Look after your body. Sit with your back supported and the screen at about eye level, and rest your eyes regularly by looking at something far away.
Tip
Pixels for photos, paths for patterns. Work in SVG; export PNG only when the design is finished.
Practice
State two differences between a raster image and a vector graphic.
What do the fill and the stroke of a shape control?
Which Inkscape tool do you use to change the shape of a path by moving its points?
A tile will be printed 10 cm wide at 300 dpi. How many pixels wide should the export be?
Uwera drew her motif in a photo-editing program. When the print shop enlarged it for a banner, the edges were blurred. Explain why, and what she should do next time.
Hands-on. Make the tile described in the hands-on section, then make two more versions with different colours. Save all three as SVG and export one as PNG at 300 dpi.
1. A raster image is made of pixels and turns blocky when enlarged; a vector graphic is made of paths and stays sharp at any size. (Also: raster suits photos, vector suits logos and patterns; PNG and JPG versus SVG and PDF.)
2. The fill is the colour inside the shape; the stroke is the colour and width of its outline.
3. The Node tool (N).
4. pixels.
5. A photo editor stores pixels, so enlarging stretches them and the edges blur. She should draw the motif as a vector (for example in Inkscape) and export at the size needed.
6. Check: three SVG files with clear names; one PNG export at 300 dpi.
Which part of the program felt easiest and which was most confusing? Write down one shortcut you will practise until you can use it without looking.
Sources and credits
