# Algorithms

**URL:** https://discourse.itk.org/c/algorithms/7.md?no_subcategories=false&page=19

[Latest](https://discourse.itk.org/latest.md) · [Categories](https://discourse.itk.org/categories.md) · [Tags](https://discourse.itk.org/tags.md)

**Page:** 20

---

## [Set up different learning rates for to-be-optimized elements](https://discourse.itk.org/t/set-up-different-learning-rates-for-to-be-optimized-elements/396)

<div class="topic-metadata">

**Author:** [@Ray](https://discourse.itk.org/u/Ray)\
**Replies:** 1\
**Last updated:** [November 6, 2017, 6:23pm UTC](https://discourse.itk.org/t/set-up-different-learning-rates-for-to-be-optimized-elements/396 "2017-11-06T18:23:03Z")

</div>

Hello! I’m using RegularStepGradientDescentOptimizerv4 to optimize a rigid registration. I want to set up a higher learning rate for translation parameters and a lower learning rate for rotation parameters. Is there any…

---

## [GradientMagnitudeImageFilter vs SobelEdgeDetectionImageFilter](https://discourse.itk.org/t/gradientmagnitudeimagefilter-vs-sobeledgedetectionimagefilter/382)

<div class="topic-metadata">

**Author:** [@AlexRothberg](https://discourse.itk.org/u/AlexRothberg)\
**Replies:** 1\
**Last updated:** [November 3, 2017, 10:57am UTC](https://discourse.itk.org/t/gradientmagnitudeimagefilter-vs-sobeledgedetectionimagefilter/382 "2017-11-03T10:57:11Z")

</div>

There are a number of edge related filters list here. I am trying to understand the difference between GradientMagnitudeImageFilter and SobelEdgeDetectionImageFilter. GradientMagnitudeImageFilter can incorporate pixel s…

---

## [Perona Malik Noise Estimator using Canny](https://discourse.itk.org/t/perona-malik-noise-estimator-using-canny/384)

<div class="topic-metadata">

**Author:** [@AlexRothberg](https://discourse.itk.org/u/AlexRothberg)\
**Replies:** 0\
**Last updated:** [November 2, 2017, 2:03pm UTC](https://discourse.itk.org/t/perona-malik-noise-estimator-using-canny/384 "2017-11-02T14:03:04Z")

</div>

In Perona and Malik, they state: a histogram of the absolute values of the gradient throughout the image was computed, and K was set equal to the 90% value of its integral My interpretation of this is to take the 9…

---

## [Multi-level neighborhood-correlation BSpline](https://discourse.itk.org/t/multi-level-neighborhood-correlation-bspline/296)

<div class="topic-metadata">

**Author:** [@Ray](https://discourse.itk.org/u/Ray)\
**Replies:** 0\
**Last updated:** [October 16, 2017, 7:08pm UTC](https://discourse.itk.org/t/multi-level-neighborhood-correlation-bspline/296 "2017-10-16T19:08:20Z")

</div>

I’m using neighborhood correlation for registration metric and BSpline for transformation model. The images are 100x100. The neighborhood window size is 10pixel-by-10pixel. The mesh size is 10x10. If I use 2-level regis…

---

## [Set up initialization in LBFGSOptimizerv4](https://discourse.itk.org/t/set-up-initialization-in-lbfgsoptimizerv4/293)

<div class="topic-metadata">

**Author:** [@Ray](https://discourse.itk.org/u/Ray)\
**Replies:** 1\
**Last updated:** [October 13, 2017, 10:41pm UTC](https://discourse.itk.org/t/set-up-initialization-in-lbfgsoptimizerv4/293 "2017-10-13T22:41:57Z")

</div>

In LBFGSBOptimizerv4, there is a method called “SetInitialPosition (const ParametersType &param)”. I wonder whether or not in LBFGSOptimizerv4 there is a similar function to set up parameter initialization. I couldn’t f…

---

## [Set up step length for LBFGSBOptimizerv4](https://discourse.itk.org/t/set-up-step-length-for-lbfgsboptimizerv4/288)

<div class="topic-metadata">

**Author:** [@Ray](https://discourse.itk.org/u/Ray)\
**Replies:** 2\
**Last updated:** [October 11, 2017, 6:18pm UTC](https://discourse.itk.org/t/set-up-step-length-for-lbfgsboptimizerv4/288 "2017-10-11T18:18:52Z")

</div>

Hello! I’m LBFGSBOptimizerv4 to perform optimization for BSpline registration. I want to set up step length for the optimizer, but it looks this class doesn’t provide this method: https://itk.org/Doxygen/html/classitk\_1…

---

## [Ray cast interpolation returns an unexpected output](https://discourse.itk.org/t/ray-cast-interpolation-returns-an-unexpected-output/255)

<div class="topic-metadata">

**Author:** [@christophe.vandijck](https://discourse.itk.org/u/christophe.vandijck)\
**Replies:** 2\
**Last updated:** [October 6, 2017, 8:38am UTC](https://discourse.itk.org/t/ray-cast-interpolation-returns-an-unexpected-output/255 "2017-10-06T08:38:10Z")

</div>

Hi fellow ITK-users, I’m trying to create several DRR images from a CT volume following several (oblique) directions. These DRRs often give unexpected results (empty images, the actual intensities not where I expected t…

[Previous page](https://discourse.itk.org/c/algorithms/7.md?no_subcategories=false&page=18)