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Interpolation Techniques
When an image is resized or rotated, the new pixel locations will not in general align exactly with the original ones, so that interpolation is needed to determine the values for the new pixels. The simplest method is select the nearest pixel to the new location. This preserves pixel values but produces visual artifacts such as stair-stepping along edges. Interpolation using the four nearest neighbors (bilinear) or a larger neighborhood of 16 pixels (bicubic) produce visually more pleasing results, but can blur fine lines and detail. This interactive tutorial illustrates the process of enlarging and rotating an image using different interpolation methods.
The tutorial initializes with a randomly selected specimen imaged in the microscope appearing in the Specimen Image window. The Choose A Specimen pull-down menu provides a selection of specimen images, in addition to the initial randomly chosen one. The Nearest Neighbor, Bilinear Interpolation, and Bicubic Interpolation buttons select the method used to generate the result image shown on the right. The Zoom Factor slider adjusts the degree of enlargement of the image, while the Angle of Rotation slider adjusts the rotation angle of the result. This slider may either be controlled directly, or the arrow buttons at either end used to change the setting.
Contributing Authors
John C. Russ - Materials Science and Engineering Dept., North Carolina State University, Raleigh, North Carolina, 27695.
Matthew Parry-Hill, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.
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