Digital art is often built in one of two main ways: vector graphics or raster graphics. Vector graphics describe images with mathematical paths, while raster graphics describe images with a grid of colored pixels. This difference matters because it affects sharpness, file size, editing style, and where the artwork works best.
A logo, icon, poster, photo, and game texture may all need different choices.
Key Facts
- Raster pixel count = width in pixels x height in pixels.
- Print size in inches = pixel dimension / PPI.
- Vector graphics use points, lines, curves, and fills defined by math.
- Raster graphics lose sharpness when enlarged beyond their original pixel dimensions.
- Approximate uncompressed raster file size = width x height x color depth in bytes.
- Common vector formats include SVG, AI, EPS, and PDF; common raster formats include PNG, JPG, GIF, TIFF, and WebP.
Vocabulary
- Vector graphic
- A vector graphic is an image made from mathematical paths that can scale up or down without losing edge sharpness.
- Raster graphic
- A raster graphic is an image made from a rectangular grid of pixels, each storing color information.
- Pixel
- A pixel is the smallest addressable picture element in a raster image.
- Resolution
- Resolution describes how many pixels an image contains or how densely pixels are printed or displayed.
- Bézier curve
- A Bézier curve is a smooth vector curve controlled by anchor points and handles.
Common Mistakes to Avoid
- Enlarging a small raster image for a poster, because the pixels become visible and edges turn blurry or blocky.
- Using JPG for a logo with flat colors and sharp edges, because JPG compression can create artifacts around clean shapes and text.
- Assuming SVG is always smaller than PNG, because detailed vector art with many paths can sometimes be larger or slower to render than a simple raster image.
- Ignoring print resolution, because an image that looks sharp on a screen may print poorly if it does not have enough pixels for the intended physical size.
Practice Questions
- 1 A raster image is 2400 pixels wide and 1800 pixels tall. How many total pixels does it contain?
- 2 A 3000 pixel wide image is printed at 300 PPI. What is the maximum print width in inches without resampling?
- 3 A designer needs artwork for a company logo that will appear on a business card, a website header, and a billboard. Should the master file be vector or raster, and why?