Information Technology • Graphics Creation

Vector or Bitmap?

Bitmap (BMP, uncompressed)

Vector (SVG)

The image
Bitmap resolution
Colour depth
FileWorked outSize

Vector or Bitmap? — Explanation

How to use it. Zoom and size shows the same logo (Rangitoto Kayaks) stored two ways, side by side. Drag the zoom: the bitmap's pixels get bigger and blockier, the vector stays sharp. Change the bitmap's resolution and colour depth, and the vector's detail, and watch the file sizes. Switch to the photo to see the other side of the story. Edit works on the layers of the vector (show, hide, reorder, scale, rotate, flip) and on the bitmap (crop, resample, colour depth, rotate). Which format? asks you to choose for real jobs.

Bitmap (raster) graphics store a grid of pixels, each with its colour.

Vector graphics store objects (shapes, lines, curves and text) as a list of instructions: each object's coordinates (its anchor points or nodes), size, fill, line colour and thickness.

Layers keep parts of an image separate, stacked from bottom to top: a layer can be hidden, moved up or down (changing what's in front), or edited without touching the others. Transformations: scale (keep the aspect ratio, or it distorts), rotate, flip (reflect) horizontally or vertically. Editing a bitmap: cropping removes the pixels outside the area kept (smaller file); reducing the resolution or the colour depth loses detail for good; rotating by any angle that isn't a multiple of 90° resamples the pixels, so each turn blurs it a little.

Common exam mistakes: saying vectors are made of pixels (they're displayed on a pixel screen, but stored as objects); saying a bitmap is "blurry" when it's enlarged (it's pixelated); thinking a vector's file size grows when it's displayed bigger; choosing vector for a photograph; forgetting that colour depth multiplies the file size; distorting a scaled image by not keeping the aspect ratio.

Objective: Cambridge International A Level IT (9626), graphics creation: the features of vector and bitmap graphics and when each is used; resolution, colour depth and file size; layers; transformations (scale, rotate, flip); cropping and other image editing; graphic file types.

Where this fits

  • AQA: AQA A Level Computer Science (7517)
  • Cambridge: Cambridge A Level Computer Science (9618); Cambridge AS Level Computer Science (9618); Cambridge A Level Information Technology (9626)
  • NCEA Level 2 Digital Technologies: 91893 Use advanced techniques to develop a digital media outcome; 91893 Use advanced techniques to develop a digital media outcome
  • Pearson Edexcel International: Edexcel International GCSE ICT (4IT1)
  • USDP: USDP Computer Science

Vector or Bitmap? — Key Terms

Key concepts in English, with te reo Māori, Chinese (Simplified) and Korean.

EnglishTe reo Māori中文（简体）한국어What it means on this page
Vector Graphicno attested term矢量图形벡터 그래픽An image stored as objects (shapes, lines, curves and text) with their coordinates and properties, redrawn at any size without losing quality.
Bitmap Graphicno attested term位图비트맵 그래픽An image stored as a grid of pixels, each with its own colour; also called a raster graphic.
Pixelpika像素픽셀(화소)The smallest dot of colour in an image.
Image resolutionno attested term图像分辨率이미지 해상도The number of pixels across and down a bitmap, e.g. 1920 × 1080.
Colour depthno attested term色深색 깊이The number of bits for each pixel; 2 to the power of it is the number of colours.
File sizeno attested term文件大小파일 크기How much storage a file needs. A bitmap's depends on its pixels and colour depth; a vector's on how many objects it has.
Pixelationno attested term像素化픽셀화When a bitmap is enlarged beyond its resolution, so its pixels show as visible squares.
Layerno attested term图层레이어A separate level of an image, stacked with others, that can be hidden, moved up or down, or edited on its own.
Aspect Rationo attested term宽高比종횡비The ratio of an image's width to its height. Keeping it when resizing stops the image being stretched or squashed.
Cropno attested term裁剪자르기(크롭)To cut away the parts of an image outside a chosen area.
Resamplingno attested term重采样리샘플링Changing the number of pixels in a bitmap, working out the new pixels from the old ones. Detail that is lost can't be recovered.

On the te reo Māori column. Terms marked as gaps have no attested equivalent in the sources checked — Karaitiana Taiuru's Dictionary of Māori Computer and Social Media Terms, Paekupu, the Reserve Bank's te reo financial glossary, NZQA and Te Aka. No coinage is printed as though it were established; where a class needs one, commission it from Te Taura Whiri i te Reo Māori and credit the translator. Te reo Māori is not italicised and takes no plural "s".