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Texture synthesis is the process of algorithmically constructing a large digital image from a small digital sample image by taking advantage of its structural content. In Mathematics, Computing, Linguistics and related subjects an algorithm is a sequence of finite instructions often used for Calculation A digital image is a representation of a two-dimensional Image using ones and zeros (binary It is object of research to computer graphics and is used in many fields, amongst others digital image editing, 3D computer graphics and post-production of films. Computer graphics are Graphics created by Computers and more generally the Representation and Manipulation of Pictorial Data Image editing encompasses the processes of altering Images whether they be digital photographs traditional analog photographs or Illustrations 3D computer graphics (in contrast to 2D computer graphics) are graphics that use a three-dimensional representation of geometric data that is stored in the computer

In few words, texture synthesis is used to fill in holes in images, create large non-repetitive background images and expand small pictures. See "SIGGRAPH 2007 course on Example-based Texture Synthesis" for more details.

Contents

Textures

Maple burl, an example of a texture.
Maple burl, an example of a texture. Acer ( maple) is a Genus of Trees or Shrubs They are variously classified in a family of their own the Aceraceae, or A burl (British bur or burr) is a tree growth in which the grain has grown in a deformed manner

"Texture" is an ambiguous word and in the context of texture synthesis may have one of the following meanings:

  1. In common speech, "texture" is a synonym for "surface structure". Texture mapping is a method for adding detail surface texture or colour to a computer-generated graphic or 3D model. Usually it comprises the five properties attributed to texture by psychology of perception: coarseness, contrast, directionality, line-likeness and roughness [1]. In Psychology and the Cognitive sciences perception is the process of attaining awareness or understanding of sensory Information.
  2. In 3D computer graphics, a texture is a digital image that is applied to a three-dimensional model via texture mapping to give objects a more realistic look. 3D computer graphics (in contrast to 2D computer graphics) are graphics that use a three-dimensional representation of geometric data that is stored in the computer Texture mapping is a method for adding detail surface texture or colour to a computer-generated graphic or 3D model. Often, such an image is a photograph of a "real" texture, such as wood grain. Wood grain describes the alignment texture and appearance of the Wood fibres
  3. In image processing, every digital image composed of repeated elements is called a "texture. Image processing is any form of Signal processing for which the input is an image such as photographs or frames of video the output of image processing can be either an image " For example, see the images below.

Texture can be arranged within a spectrum from Stochastic to Regular:

These extremes are connected by a smooth transition, as visualized in the figure below from "Near-regular Texture Analysis and Manipulation." Yanxi Liu, Wen-Chieh Lin, and James Hays. SIGGRAPH 2004

The texture spectrum

Aim

The aim of a texture synthesis algorithm is to create an output image that meets the following requirements:

Moreover, it shall meet the usual requirements of algorithms: efficiency in terms of speed and economy in terms of memory.

Methods

The following methods and algorithms have been researched or developed for texture synthesis:

Tiling

The plainest way to create a larger image from a sample image is by simply tiling it. That means the output image is tiled together from duplicates of the sample image, in a simple copy-and-paste manner. For a pejorative meaning see Cut and paste job In Human-computer interaction, cut and paste and copy and paste offer The result is usually unsatisfactory: unless the sample complies with special requirements, the seams between the tiles will be plainly visible, and even then still the output image will be highly repetitive.

Stochastic texture synthesis

An algorithm of that family produces an image by randomly choosing colour values for each pixel, only influenced by basic parameters like minimum brightness, average colour or maximum contrast. These algorithms perform well with stochastic textures only, otherwise they produce completely unsatisfactory results as they ignore any kind of structure within the sample image.

Single purpose structured texture synthesis

Algorithms of that family use a fix procedure to create an output image, i. e. they are limited to a single kind of structured texture. Thus, these algorithms can both only be applied to structured textures and only to textures with a very similar structure. For example, a single purpose algorithm could produce high quality texture images of stonewalls; yet, it is very unlikely that the algorithm will produce any viable output if given a sample image that shows pebbles.

Chaos mosaic

This method, proposed by the Microsoft group for internet graphics, is a refined version of tiling and performs the following three steps:

  1. The output image is filled completely by tiling. The result is a repetitive image with visible seams.
  2. Randomly selected parts of random size of the sample are copied and pasted randomly onto the output image. The result is a rather non-repetitive image with visible seams.
  3. The output image is filtered to smooth edges.

The result is an acceptable texture image, which is not too repetitive and does not contain too many artifacts. Still, this method is unsatisfactory because the smoothing in step 3 makes the output image look blurred.

Pixel-Based Texture Synthesis

These methods, such as "Texture Synthesis by Non-parametric Sampling." Efros and Leung, ICCV, 1999, "Fast Texture Synthesis using Tree-structured Vector Quantization" Wei and Levoy SIGGRAPH 2000 and "Image Analogies" Hertzmann et al. SIGGRAPH 2001. are some of the simplest and most successful general texture synthesis algorithms. They typically synthesize a texture in scan-line order by finding and copying pixels with the most similar local neighborhood as the synthetic texture. These methods are very useful for image completion. They can be constrained, as in "Image Analogies", to perform many interesting tasks. They are typically accelerated with some form of Approximate Nearest Neighbor method since the exhaustive search for the best pixel is somewhat slow. The synthesis can also be performed in multiresolution, such as "Texture synthesis via a noncausal nonparametric multiscale Markov random field." Paget and Longstaff, IEEE Trans. on Image Processing, 1998.

Patch-Based Texture Synthesis

Patch-based texture synthesis creates a new texture by copying and stitching together textures at various offsets. "Image Quilting." Efros and Freeman. SIGGRAPH 2001 and "Graphcut Textures: Image and Video Synthesis Using Graph Cuts." Kwatra et al. SIGGRAPH 2003 are the best known patch-based texture synthesis algorithms. These algorithms tend to be more effective and faster than pixel-based texture synthesis methods.

An example of Efros and Freeman's Image Quilting.

Chemistry based

Realistic textures can be generated by simulations of complex chemical reactions within fluids, namely Reaction-diffusion systems. Reaction–diffusion systems are mathematical models that describe how the concentration of one or more substances distributed in space changes under the influence of two processes local It is believed that these systems show behaviors which are qualitatively equivalent to real processes (Morphogenesis) found in the nature, such as animal markings (shells, fishs, wild cats. MOrphogenesis is an EP by Industrial Black metal band.And Oceans. . . ). See also Turing patterns.

Literature

Several of the earliest and most referenced papers in this field include:

Popat in 1993 - "Novel cluster-based probability model for texture synthesis, classification, and compression".

Heeger-Bergen in 1995 - "Pyramid based texture analysis/synthesis".

Paget-Longstaff in 1998 - "Texture synthesis via a noncausal nonparametric multiscale Markov random field"

Efros-Leung in 1999 - "Texture Synthesis by Non-parameteric Sampling".

Wei-Levoy in 2000 - "Fast Texture Synthesis using Tree-structured Vector Quantization"

although there was also earlier work on the subject, such as

(The latter algorithm has some similarities to the Chaos Mosaic approach).

The non-parametric sampling approach of Efros- Leung is the first approach that can easily synthesis most types of texture, and it has inspired literally hundreds of follow-on papers in computer graphics. Since then, the field of texture synthesis has rapidly expanded with the introduction of 3D graphics accelerator cards for personal computers.

A similar technique for audio rather than images is known as Granular synthesis. Granular synthesis is a basic sound synthesis method that operates on the Microsound time scale.

References

  1. ^  Tamura et al. (1978)

External links

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