Interpolations are mathematical procedures with which missing information between two points of a line is calculated. For displays and projectors, it is the adaptation of an image format to be displayed to the nativescreen resolution of the display or projector. For example, the CCIR format720 x 576, if it is to be displayed on an LCD display with a resolution of 1,024 x 768, is interpolated.
Interpolation of displays involves mathematically calculating additional pixels that are located between other pixels. Interpolation methods are used to increase the apparent resolution of graphics, images and photos. The resolution itself cannot be changed by interpolation, since no additional details are generated.
Mathematical interpolation methods include pixel repetition, linear interpolation, higher degree interpolation and spline interpolation. In the simplest method of pixel repetition, no new pixel value is calculated, but the previous pixel is taken over unchanged. In linear inter polation, a straight line between two reference points is determined and all points lying on it are calculated individually. In higher degree interpolation, higher degree polygons are used and in spline interpolation, the interpolation is done by using Bezier curves. If the interpolation takes place two-dimensionally, these procedures can be used in both image axes. A distinction is made between bilinear and bicubic interpolation.
In bilinear interpolation, the value for the interpolated pixel is calculated from the four neighboring pixels. In contrast, the bicubic method uses the values of eight neighboring pixels and calculates the interpolated value from them.