Raster Images vs Vector Graphics
There are two types of digital graphics files – vector and raster. Vector images are made of hundreds of thousands of tiny lines and curves (or paths) to create an image. Raster images are composed of pixels. These pixels contain bits of color and when combined, they build images.
Raster images are often called bitmap images because they are made of millions of tiny squares, called pixels. You can identify a raster or bitmap image by looking at it very closely. If you zoom in enough, you will be able to see the square outlines of each pixel (especially around edges where there are dramatic color contrasts).
Raster graphics typically have larger file sizes than their vector counterparts. Higher DPI (dots per inch) and PPI (pixels per inch) settings also contribute to larger files because software must keep track of and be able to render each pixel. File size can become a concern if storage or server space is limited or if files have to be transmitted electronically.
Unlike pixel-based raster images, vector graphics are based on mathematical formulas that define geometric primitives such as polygons, lines, curves, circles and rectangles. Because vector graphics are composed of true geometric primitives, they are best used to represent more structured images, like line art graphics with flat, uniform colors. Most created images (as opposed to natural images) meet these specifications, including logos, letterhead, and fonts.
Common raster file types:
Raster files are saved in various formats:
- .tiff (Tagged Image File Format)
- .psd (Adobe Photoshop Document)
- .pdf (Portable Document Format)
- .jpg (Joint Photographics Expert Group)
- .png (Portable Network Graphic)
- .gif (Graphics Interchange Format)
- .bmp (Bitmap Image File)
Popular raster-based image editors:
- Adobe Photoshop
Common vector file types:
Vector files can be saved or edited in these formats:
- .ai (Adobe Illustrator document)
- .eps (Encapsulated PostScript)
- .svg (Scalable Vector Graphic)
- .pdf (Portable Document Format; only when saved from vector programs)
Popular vector-based image editors:
- Adobe Illustrator