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Bitmap Graphics

Formats

Store colors pixel by pixel:

Such files can get pretty big: Size in bytes = width * height * bytes per pixel. Thus, one needs compression techniques:

Programming

Basic Effects

Antialiasing

Aliasing: generation of spurious frequencies due to sampling of frequencies of half the sampling rate or more. Note that “frequency” may also mean lines per inch, not only periods per second. This occurs in:

There is a huge variety of countermeasures, all called “antialiasing”. The basic approach is to limit the range of frequencies before sampling. It is virtually impossible to filter after aliasing has been created; one has to filter before sampling at the intended sampling rate. One simple approach to this is supersampling: Sample at several times the intended rate, then filter digitally and resample digitally at the intended rate. This is employed for images, films, and audio all alike.

The filtering leads to smooth transitions as can be seen in antialiased font rendering. Note that Microsoft's ClearType applies shifted filters for each R, G, and B subpixel, thus achieving a higher spatial resolution.

Interpolation

Another issue related to the discreteness of the pixels is interpolation: To compute arbitrarily scaled, rotated or warped versions of an image, one has to determine color values "between" the pixels of the given image. Standard interpolation methods: