Tuesday, August 05, 2008

Raster vs Vector

This is a copy of a post I made on Shutterstock in reference to someone's question about raster and vector images and is simplified a bit, but should be helpful to someone who is still trying to figure out the whole raster/bitmap vs vector thing.

In a very basic nutshell... bitmap and raster are used interchangeably. That format is basically represented by x number of pixels (dots) and each of those pixels has a color. If you zoom all the way in to an image (like a photograph) you see big dots and each one has a color. That's a raster image or more commonly referred to as a bitmap image. With one of these raster images, like a picture, you can make it smaller if you need to, but you can't really make it much larger (called upsizing) than it is without a serious degradation in quality. Some common bitmap files are .png, .jpg, .gif, .tga, .tif and .bmp.

A vector image is made up (again, simplifying) of math commands that say "go here and draw this kind of line" or "go here and draw a circle of x radius" -- but of course, we don't create those images that way, thankfully! As a result, you can't really zoom "all the way" to a vector image to see the dots or pixels. As a result, a vector can be resized to whatever size it needs to be. So vector images can be upsized/resized to any size that someone might need, from an icon to a 300 dpi billboard (which would be insane). Illustrator is the most common program used to create vector images. Flash is probably the other really well known program that makes vectors, though it's not really referred to as such and isn't really built for making "vector images" as much as interactive stuff. Inkscape is a free vector creation program, and it's quite nice. An .eps file is an example of a vector file, along with .ai files.

To confuse the issue further, you can import pictures (aka rasters or bitmaps) into flash or illustrator but if you're doing a true vector illustration you won't want to do that.

If you're doing stock images, when you're done making your vector image in Inkscape, you need to export the vector version (.eps) for upload to your favorite site as well as a raster version (which you export from inkscape as .png and convert to .jpg) which you create from within inkscape by doing Export->PNG.

It's all a bit confusing, but once you jump into it, it'll make more sense.

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