Bitmaps and Vectors - the Difference

There are two quite different techniques for creating, storing and processing computer images: bitmap graphics and vector graphics.

This page just defines the two types as simply as possible. You will find links to more detailed descriptions at the bottom.

Bitmaps

A bitmap image is a computer file used to store a picture. It consists of tiny blocks called pixels:

a 4 x 3 pixel image = 12 pixels total

The image above consists of just 12 pixels so in reality would appear as no more than a small grey dot. The gaps you see between the pixels do not really exist – they are just shown for clarity.

Imagine each pixel to be like a tiny square light bulb. Each pixel can be any colour you want and any brightness.

You cannot light up part of a pixel.

Real images are of course a lot more complex and consist of many more pixels.

The example below is still rather blocky and crude, but you can begin to see how a picture can be made up from pixel building blocks:

Squint at the image, or step back from your monitor and you will see it is a close up image of an eye. In real bitmap images, the pixels are tiny dots so the illusion of a smooth and realistic image is created:

Vectors

Programs like Flash draw using vectors. A very simple vector drawing might look like this:

In a vector drawing, you create control points. The lines in a vector drawing are created by the software and join up the control points that the user has drawn. There are 4 control points in the drawing above (3 are little white squares, the last one is dark to indicate that it is being worked on). There is far more to be explained about vector graphics, but hopefully the illustration above will be enough for you to see immediately how vector graphics differ from bitmap graphics.

That concludes our brief look at the difference between bitmap and vector graphics.
Be aware that although almost every graphics program you encounter will be primarily a vector ("drawing") or bitmap ("painting") program, it will probably offer both types of graphic and the chance to mix them together.

Advantages of bitmaps

• in paint programs, you see what you are getting, usually in real time when wielding a “paintbrush”
• when you use a scanner, the output will normally be a bitmap
• much easier to create the appearance of “natural” media, such as areas of watercolours bleeding into each other
• more universally available interchange file formats; most bitmaps can be read by most bitmap-based software and certain file formats such as jpeg and png can be read and written by every paint program. This is not, unfortunately, the case with vector file formats where many programs can only deal with their own file formats and a very limited choice of others such as eps may be available.

Advantages of vectors

• pretty much resolution-independent. It is possible to rescale up a whole chunk of animation without the blockiness you would get from doing this with bitmaps
• for painting, you can specify that the bounding lines are automatically closed even when not visible, so avoiding problems of paint flooding out
• shapes easily edited
• smaller output files for Internet use
• shapes can be made to animate automatically from one to another, providing they have the same number of control points

Painting and drawing programs continue to evolve; one common feature is that both type of program incorporate more and more elements of the other type; painting programs have more drawing features in them and drawing programs have more painting features.
In some drawing software, it is possible to create graphics that look like typical bitmaps, (say, with airbrush lines, for example), yet still remain vectors and so be editable.
Some software can do a good job of transforming a given bitmap into a vector graphic, though there is always a loss of detail involved.

For outputting to the Web and for printwork, much software, (Flash etc.) is vector based. For TV and film, regardless of how the artwork was originated, the final output format will always be a bitmap one.

more about bitmaps          more about vector graphics

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