# What is the difference between vector and raster images?

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• Anonymous

There are two kinds of computer graphics - raster (composed of pixels) and vector (composed of paths). Raster images are more commonly called bitmap images.

A bitmap image uses a grid of individual pixels where each pixel can be a different color or shade. Bitmaps are composed of pixels.

Vector graphics use mathematical relationships between points and the paths connecting them to describe an image. Vector graphics are composed of paths.

• Anonymous

OK, we do a whole class on this, but here it is in a nutshell:

Computer screens display pictures with a grid of dots. Each dot is a specific color. The colors are (usually) stored in a three-number sequence, for the amount of red, green, and blue in the particular dot.

Any picture you see on a computer screen is stored with some variation of this scheme. This is called a 'raster' image. Raster images are good because they are closely related to the display technology (monitors, printers, and whatever else).

Raster images have weaknesses, though.

They are very wasteful. An uncompressed image that fills the screen can weigh in at over eight megabytes (that's why we almost never use uncompressed images)

Raster images are also notoriously difficult to scale. You can take a big picture and make it smaller without too many problems (except of course the smaller picture contains less data) You can't take a small picture and make it bigger. If you try to enlarge a raster image, you will get blocky results, no matter what they show you on every -stinking- episode of CSI (wait, did I rant there? sorry.)

Vector graphics are described differently. A vector graphic works by storing the math formulas needed to draw a picture. If the image contains mainly geometric shapes, this can be very efficient. For example, a circle may only require four pieces of data: X, Y, radius, and color. It doesn't matter how large the circle is, it only requires those same elements.

Another advantage of vector images is how easy they are to modify. If you want to change the size, you just multiply the radius. If you want to rotate something, you just apply another formula. (Actually the software usually does all the math. Most people using vector software are unaware of all the calcuations going on under the hood.)

Vector images scale very well, but they aren't perfect either: A vector image's file size depends on the complexity. A photo will not be efficiently stored as a vector image. Vector images are harder on the computer because they require more processing power than raster images. Computers usually can't display vector images directly, but must convert them to raster images on the fly.

The most common software for working with raster images is PhotoShop (although there are many others.) The most popular open-source raster tool is Gimp, which is almost as powerful as PhotoShop and free.

A number of tools work with various vector formats, including Adobe Illustrator and Flash. SVG is a common vector format in the open-source world, with some very promising tools emerging including inkscape and dia.

• Anonymous

A "vector" image is drawn with a single gun that continuously "draws" the image on the screen. I have not seen a color vector display. These are typical of radar and other air traffic control displays. They are typically capable of very high resolution. They are still in use today on the B1 bomber (I've been on the flight deck and seen them).

A raster image is painted on the screen in stripes of dots. It can be color or monochrome. To achieve this, the image is laid out in memory and the video driver walks over the image a stripe at a time--the stripes being one pixel wide. This binary data is displayed by the monitor and refreshed on the screen 60-90 times a second until it's changed. This is what all modern computer monitors use.

• 4 years ago

Vector drawings are based on points and the lines connecting them. You can zoom in to any level and still maintain smooth lines. You create these types of images with tools like Adobe Illustrator. Raster (or bitmap) images are made up of pixels (dots). The more pixels, the more detail the image could hold. If you zoom in far enough on a raster image you can see the pixels. You can create images like this with Adobe Photoshop. Your digital camera also captures this type of images. Most all of the images you see on the internet are raster images. Vector based images are usually used for print work (because they can scale up very large and still look good).

vector images are calculated mathematically, and usually created by modifying basic shapes. the advantage to this is that it can be expanded to any size without loss of quality. they usually have less detail than raster images. it is possible to create high detail vector art though. here is a vector art sample:

http://io-noi-aldo.sonance.net/blogpix/a_linha_vec...

note the flat colors and crisp borders.

they usually come in .pdf or .ai format. they will not come in formats such as .jpeg or .gif

oh right, the image above is a jpeg version of the vector image. that is, it was converted to be compatible with all computers.

raster images are comprised of little squares (pixels) of varying colors. all jpegs and gifs are raster images. when you blow them up, you are only expanding the little squares that make them up, so at some point, all you will see are giant squares of color. it is easier to add detail or modify detail on a raster image (just paint over it) and effects such as glows are very easy to apply to it. of course, you wont need a sample.