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Encyclopedia > Image scaling

In computer graphics, image scaling is the process of resizing a digital image. Scaling is a non-trivial process that involves a trade-off between efficiency, smoothness and sharpness. As the size of an image is increased, so the pixels which comprise the image become increasingly visible, making the image appear "soft". Conversely, reducing an image will tend to enhance its smoothness and apparent sharpness. A digital image is a representation of a two-dimensional image as a finite set of digital values, called picture elements or pixels. ... This example shows an image with a portion greatly enlarged, in which the individual pixels are rendered as little squares and can easily be seen. ...


Apart from fitting a smaller display area, image size is most commonly decreased (or subsampled or downsampled) in order to produce thumbnails. Enlarging an image (upsampling or interpolating) is generally less common. The main reason for this is that in "zooming" an image, it is not possible to discover any more information in the image than already exists, and image quality inevitably suffers. However, there are several methods of increasing the number of pixels that an image contains, which evens out the appearance of the original pixels. In computer graphics, subsampling (or downsampling) is the process of reducing an image to a smaller size. ... The ThumbsPlus image file manager showing folder tree in the upper left and 12 thumbnail-size images to the right. ... In numerical analysis, a branch of mathematics, bicubic interpolation is one of the most common interpolation methods in two dimensions. ...


Scaling methods

An image size can be changed in several ways. Consider doubling the size of the following image:


Image:Image-before-scaling.png Image File history File links No higher resolution available. ...


The easiest way of doubling its size is nearest neighbour interpolation, replacing every pixel with four pixels of the same color: Example of nearest neighbor interpolation of a set of points in 2D Nearest neighbor interpolation is a simple method of interpolation. ...


Image:Image-after-trivial-scaling.png Image File history File links No higher resolution available. ...


The resulting image is larger than the original, and preserves all the original detail, but has undesirable jagginess. The diagonal lines of the W, for example, now show the characteristic "stairway" shape. jaggies are those sharp edges that you see in all the wii games Jaggies is the informal name for aliasing artifacts in raster images, often caused by non-linear mixing effects producing high-frequency components and/or missing or poor anti-aliasing filtering prior to sampling. ...


Other scaling methods are better at preserving smoooth contours in the image. For example, bilinear interpolation produces the following result: In mathematics, bilinear interpolation is an extension of linear interpolation for interpolating functions of two variables. ...


Image:Image-after-linear-interpolation.png Image File history File links No higher resolution available. ...


Linear (or bilinear, in two dimensions) interpolation is typically better than the nearest-neighbor system for changing the size of an image, but causes some underiable softening of details and can still be somewhat jagged. Better scaling methods include bicubic interpolation: In numerical analysis, a branch of mathematics, bicubic interpolation is one of the most common interpolation methods in two dimensions. ...


Image:Image-after-cubic-interpolation.png Image File history File links No higher resolution available. ...


See also

2xSaI is a digital image processing algorithm for computer graphics. ... In numerical analysis, a branch of mathematics, bicubic interpolation is one of the most common interpolation methods in two dimensions. ... In mathematics, bilinear interpolation is an extension of linear interpolation for interpolating functions of two variables. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... In the mathematical subfield of numerical analysis, spline interpolation is a form of interpolation where the interpolant is a special type of piecewise polynomial called a spline. ...

External links


  Results from FactBites:
 
Olympus MIC-D: Cropping, Zooming, and Repositioning Digital Images - Interactive Java Tutorial (1727 words)
Zooming to enlarge image details is useful for the visualization of small structures present in a digital image, and scaling is often necessary to format a digital image to fit within the boundaries of a display medium, as in the case of displaying a collection of thumbnail images.
Image rotation is performed at 90-degree intervals in the tutorial (and also in the MIC-D software), with the center of the image serving as the rotational origin.
Scaling is a useful operation for formatting a digital image to fit within the bounds of a display medium, as in the case of displaying a collection of thumbnail images.
  More results at FactBites »

 
 

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