TopHatTransform [image,ker]
gives the morphological top-hat transform of image with respect to structuring element ker.
TopHatTransform [image,r]
gives the top-hat transform with respect to a range-r square.
TopHatTransform [data,…]
applies top-hat transform to an array of data.
TopHatTransform
TopHatTransform [image,ker]
gives the morphological top-hat transform of image with respect to structuring element ker.
TopHatTransform [image,r]
gives the top-hat transform with respect to a range-r square.
TopHatTransform [data,…]
applies top-hat transform to an array of data.
Details
- Top-hat transform is a morphological operation used for enhancing small bright regions in an image, and can be used to remove uneven background illumination or extract features.
- BottomHatTransform is effectively the same as subtracting the morphologically opened image from the image.
- TopHatTransform works with binary, grayscale, and other images.
- TopHatTransform works with 3D as well as 2D images, and also with data arrays of any rank.
- The structuring element ker is a matrix containing 0s and 1s.
- TopHatTransform automatically pads structuring elements to have odd dimensions.
- TopHatTransform [image,r] is equivalent to TopHatTransform [image,BoxMatrix [r]].
- If multiple image channels are present, TopHatTransform operates on each of them separately.
- TopHatTransform preserves regions smaller than the structuring element whose channel values are larger than their surroundings.
Examples
open all close allBasic Examples (4)
Extract thin lines from a multichannel image:
Remove disks larger than the structuring element:
Correct uneven illumination to count grains of rice:
Correct uneven illumination and remove the large feature:
Applications (4)
Extract small, bright regions from a color image:
Subtract from the original image to remove small features:
Locate small, bright regions of a specific color channel:
Use the mask as the alpha channel:
Correct uneven background illumination in a grayscale image:
Isolate the lightning in an image:
Interactive Examples (1)
Use Manipulate to extract successively larger objects:
See Also
Related Guides
Text
Wolfram Research (2008), TopHatTransform, Wolfram Language function, https://reference.wolfram.com/language/ref/TopHatTransform.html (updated 2012).
CMS
Wolfram Language. 2008. "TopHatTransform." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2012. https://reference.wolfram.com/language/ref/TopHatTransform.html.
APA
Wolfram Language. (2008). TopHatTransform. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/TopHatTransform.html
BibTeX
@misc{reference.wolfram_2025_tophattransform, author="Wolfram Research", title="{TopHatTransform}", year="2012", howpublished="\url{https://reference.wolfram.com/language/ref/TopHatTransform.html}", note=[Accessed: 04-January-2026]}
BibLaTeX
@online{reference.wolfram_2025_tophattransform, organization={Wolfram Research}, title={TopHatTransform}, year={2012}, url={https://reference.wolfram.com/language/ref/TopHatTransform.html}, note=[Accessed: 04-January-2026]}