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LabelOverlayImageFilter colorize a label image and put it on top of the input image.

Improving features and performance of binary erode and dilate filters

Published in The Insight Journal

Published in The Insight Journal

Binary erosion and dilation are the base filters of binary mathematical morphology.
In ITK 2.4.1 verb$BinaryDilateImageFilter$ and verb$BinaryErodeImageFilter$ implement
an efficient algorithm described in cite{Nikopoulos2000}. However, those filter lack [...]

InvertIntensityImageFilter is a convenient filter to invert the intensity of an image.

Binary morphological closing and opening image filters remove structures smaller than the structuring element in a binary image.

Morphological gradients enhance the variation of pixel intensity in a given neighborhood.

ModulusImageFilter is a simple image filter to compute the modulus (x % dividend) pixel-wise.

Component tree: an efficient representation of grayscale connected components

Published in The Insight Journal

Published in The Insight Journal

Connected component is a well known and very useful notion in binary case. As often in mathematical morphology, this notion can be extended to the grayscale case, and allow to perform lot of the useful transforms based on binary connected components in the [...]

Robust Automatic Threshold Selection (RATS) is a fast and noise robust
automatic thresholding method based on gradients in the image. The basic idea is to choose
the threshold at the intensity where the gradient are the highest.

While filtering in N dimensions is a main feature of ITK, filtering an image
in N-1 dimensions, slice by slice, can be very useful in many cases. Currently,
this operation require a consequent amount of work to be done with ITK. A new
filter is provided [...]

The Fourier transform of the convolution of two images is equal to the product of their
Fourier transform. With this definition, it is possible to create a convolution filter
based on the Fast Fourier Transform (FFT). The interesting complexity [...]

Several kind of noise can be found in real images, mostly depending on the modality
of acquisition. It is often useful to be able to simulate that noise, for example
to test the behavior of an algorithm in the presence of a known amount of noise.
This [...]

The tophat transform is a well know and widely used transform based of morphological opening or closing. It is often used to remove the background in an image, where the background is defined as the zones which do not fit in the user provided [...]

A common usage when working with Fourier transform is to shift the
the image to put the zero-frequency component in the center of the
image. This contribution comes with a filter to perform this
transform.

Two simple filters are contributed to compute the exponential of an image: the first one to raise the image to the power of a constant, the other one to raise the image to the power of the values provided in another image.

ly in ITK, the only way to find the contour of the objects in a binary image is to use the BinaryErodeImageFilter, with a kernel of radius 1. This filter is a generic filter, made to support any shape and size of structuring element, and thus is not optimized [...]

A filter to impose to the input image the minima defined in the marker image.

Image projection is a very common task in image analysis to reduce the dimension of an image. A base filter is provided, with some specialized filters which implement different projection methods.

Richard Beare has recently introduced a new filter to efficiently labelize the connected components with ITK, and has also proposed to use the run-length encoding used in that filter to implement some of the most useful binary mathematical morphology [...]

Combining some labeled images is a quite common and useful task in image analysis.
That's something we may want to do to prepare the markers for a watershed from
markers for example, or to write the output of several segmentations in a single
file.
This [...]

The deconvolution, also called deblurring, tries to revert the optical distortion introduced during the aquisition of the image. It is a family of image processing which can be classed in the larger family of image restoration.
Deconvolution is a very [...]

When an image is mostly composed of background pixels, most of the automatic
thresholding methods are failing to produce a relevant threshold. This is mainly
caused because one mode is over represented compared to the other in the histogram
of the image. [...]

This report discusses various definitions and implementations of the watershed transform as well as providing an introduction to some well known techniques for applying the watershed transform to practical problems. The discussion will be focused on new and [...]

Efficient N-Dimensional surface estimation using Crofton formula and run-length encoding

Published in The Insight Journal

Published in The Insight Journal

Unlike the measure of the area in 2D or of the volume in 3D, the perimeter and the surface are not easily measurable in a discretized image.
In this article we describe a method based on the Crofton formula to measure those two parameters in a discritized [...]

Finding regional extrema of images is an important step in a number of
morphological algorithms, such as some versions of the watershed
transformfootnote{This work started because we were trying to compare
different watershed algorithms}. Regional extrema [...]

Grayscale dilation and erosion are basic transformations of mathematical morphology. Used together
or with other transformations, they are very useful tools for image analysis. However, they can be very
time consuming, especially with 3D images, and with [...]

Kernel based filtering is one of the fundamental tools of image
analysis and processing. A number of approaches have been developed
over the years that allow efficient implementation of such filters
even when the kernel size is large. This article reviews [...]

ITK is a huge image analysis library, which contains lots of state of the arts
algorithms implementations. However, using it in C++ can be difficult and is
definitively bad suited for prototyping. WrapITK aims to allow classes from ITK
(and custom, classes [...]

Meeting Andy Warhol Somewhere Over the Rainbow: RGB Colormapping and ITK

Published in The Insight Journal

Published in The Insight Journal

Although greyscale intensity values are primarily used in image data visualization oftentimes, due to the requirements of aesthetics (whether they be self-imposed or collaborator-suggested), mapping the greyscale image to a user-defined colormap is desired. [...]

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