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I understand from prior knowledge that there are two different image format / composition options available for creating images; raster and vector.

I would like to understand more about them, such as what the defining characteristics of each are, and what typical, generic use-cases each might have.

  1. What are raster graphics composed of?

    • When would I want to choose raster over vector?

  1. What are vector graphics composed of?

    • When would I want to choose vector over raster?
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  • "When would you use vs the other" is a bit broad I think. A bit more context would be needed (because in digital media, you'll often have to use raster images even if vector would be the "right thing")
    – Pekka
    Commented Jan 6, 2011 at 18:00
  • I'm just looking for typical examples in an ideal world. I understand that often you have to use raster images, but I'm just looking for the generic use cases.
    – PearsonArtPhoto
    Commented Jan 6, 2011 at 18:56

4 Answers 4

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Vector graphics are graphics in which the image is represented in a mathematical fashion. What this allows one to do is to zoom in an image to infinite precision. They are ideal for situations in which an image might be used at various resolutions and dimensions.

Raster graphics are of a fixed dimension, somewhat like a grid pattern with specified values at each point. These graphics are the default for things from the real world (IE, scanned images, photographs, etc). They are ideal for use when an image will only be used once, and will never need to be enlarged, or if portions are coming from a photograph or other real-world image.

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    to add to Pears answer: Vector images are good for Logos, and Icons, when the size is indeterminate. Raster images are good for backgrounds and photos, when you know how big you want something to be.
    – zzzzBov
    Commented Jan 6, 2011 at 21:42
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enter image description here

(that's Illustrator on the left, Photoshop on the right)

Raster images are just grids of pixels, like what comes out of a digital camera or a scanner. The file doesn't know what those pixels mean. Web images and digital paintings are most often raster.

  • Adobe Photoshop, GIMP, Krita, Corel Photopaint and Pixelmator are primarily raster (some have a few very basic vector tools too, but the images they create are raster).
  • Most digital painting programs and apps like ArtRage, Sketchbook, Layerpaint and Procreate are raster.
  • JPG, GIF, PNG, TIFF, BMP are all common raster image formats. PSDs (Photoshop files) are raster too (but can sort-of contain sort-of vector shapes). PDFs can contain both.

Vector images are made of separate shapes, lines, paths etc. They're more flexible as each shape is separate and you can scale up and down as much as you like, but it's harder to make the images look natural.

  • Adobe Illustrator, Inkscape, Sketch, Affinity Designer and Corel Draw are primarily vector (although some have a few tools that add raster effects).
  • Most CAD and 3D rendering programs like AutoCAD, Maya, Blender and Cinema4D work with (more complex) vectors.
  • EPS, SVG and AI (Illustrator) are the most common vector formats. They can all contain embedded raster images. PDFs can contain both - it's good practice to produce PDFs where everything that can be vector is, and only things like photos are raster.

In general, if you can use vector, it's a good idea to. It'll be more flexible for scaling, easier to edit, and you won't have to worry about the resolution being high enough for print (vector images have infinite resolution).

It's common to work with a mix of the two e.g. where you have a photo and other elements.

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@Pearsonartphoto already puts it nicely. In an effort to find the shortest possible definition that is still correct:

  • Vector graphics are a collection of geometrical elements (primitives like circles, squares, triangles... as well as polygons and curves) that you can enlarge to any size.

  • Raster (Pixel) graphics is a collection of coloured dots. You can't enlarge it without the dots starting to show.

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  • Resizing the raster graphic down doesn't degrade the image as much as enlarging, though.
    – Jari Keinänen
    Commented Jan 6, 2011 at 18:26
  • @koiyu cheers, I meant "enlarge". Fixed
    – Pekka
    Commented Jan 6, 2011 at 18:26
  • @koiyu It doesn't at all, if you use Super Sampling.
    – Mateen Ulhaq
    Commented Jan 7, 2011 at 5:05
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NOTES: Inkscape would be an example of a Vector Graphics editor, while GIMP/Photoshop/Paint.NET/etc are suited to editing raster images.

Ever notice that as you zoom into an image, the quality gets lower? That's a raster image. A raster image is like the one your digital camera takes. They are usually in the formats JPG (lossy), GIF (lossless), PNG (my favorite; lossless), and many others.

This is a Raster Graphics editor in action:

Paint.NET

Meanwhile, vector images are in the format of SVG, and some others. Their applications are not usually for everyday use. (Ordinary people don't use vector graphics.) You can't upload .svg files, normally, and not everyone has an editor (even though Inkscape is free).

They're based on the mathematical idea of vectors:

Vectors

Vector graphics can do more than just lines, though. They can draw other "primitives" like squares, circles, curves.

Here's an image that explains the difference best: http://en.wikipedia.org/wiki/File:VectorBitmapExample.svg

Notice I couldn't upload because it was in .svg (vector) format. You CAN convert it to a raster, though, but I was too lazy.

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