median blur filter
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| median blur filter | Julien Hardelin | 30 Oct 15:01 |
| median blur filter | Ell via gimp-docs-list | 31 Oct 01:34 |
| median blur filter | Julien Hardelin | 31 Oct 06:45 |
| median blur filter | Ell via gimp-docs-list | 31 Oct 07:23 |
| median blur filter | Julien Hardelin | 31 Oct 13:53 |
median blur filter
Hi all,
I don't understand the "Alpha percentile" option in Median Blur filter.
Is this "alpha" a term related to statistics or to transparency ? I can't built an example of this option.
Please, give me this example.
Julien
median blur filter
On 10/30/18 11:01 AM, Julien Hardelin wrote:
Hi all,
I don't understand the "Alpha percentile" option in Median Blur filter.
Is this "alpha" a term related to statistics or to transparency ? I can't built an example of this option.
By default, the Median Blur filter finds the median value at the neighborhood of each pixel. In spite of its name, the filter can actually find *any* arbitrary percentile, not just the median (i.e., the 50th percentile). The "Percentile" parameter controls the percentile used for the color components, and the "Alpha percentile" parameter separately controls the percentile used for the alpha component. In other words, "alpha" is related to transparency in this context.
To see the effect of this parameter, you need an image with transparency -- if the alpha channel is opaque everywhere, the result will also be fully opaque, regardless of the percentile. Much like the color "Percentile" parameter, for which lower values shift the image toward darker tones and higher values toward brighter ones, lower values for the "Alpha percentile" parameter shift the image toward more transparency, and higher values shift the image toward more opacity, where a value of 50% is balanced. Roughly speaking, values less than 50% make the opaque regions of the image smaller, while values greater than 50% make the opaque regions of the image larger.
-- Ell
median blur filter
Thank you Ell for your quick answer.
When I read your explanation, I have a feeling that I understand. But when I try to apply this, I get nothing. I tried with an alpha channel, a layer mask, a selection mask (where I can edit transparency) without any result in the image.
Please, give me an example applying this damned Alpha percentile. I am sure that I will understand with an example.
Julien
Le 31/10/2018 à 02:34, Ell via gimp-docs-list a écrit :
On 10/30/18 11:01 AM, Julien Hardelin wrote:
Hi all,
I don't understand the "Alpha percentile" option in Median Blur filter.
Is this "alpha" a term related to statistics or to transparency ? I can't built an example of this option.
By default, the Median Blur filter finds the median value at the neighborhood of each pixel. In spite of its name, the filter can actually find *any* arbitrary percentile, not just the median (i.e., the 50th percentile). The "Percentile" parameter controls the percentile used for the color components, and the "Alpha percentile" parameter separately controls the percentile used for the alpha component. In other words, "alpha" is related to transparency in this context.
To see the effect of this parameter, you need an image with transparency -- if the alpha channel is opaque everywhere, the result will also be fully opaque, regardless of the percentile. Much like the color "Percentile" parameter, for which lower values shift the image toward darker tones and higher values toward brighter ones, lower values for the "Alpha percentile" parameter shift the image toward more transparency, and higher values shift the image toward more opacity, where a value of 50% is balanced. Roughly speaking, values less than 50% make the opaque regions of the image smaller, while values greater than 50% make the opaque regions of the image larger.
-- Ell
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median blur filter
On 10/31/18 2:45 AM, Julien Hardelin wrote:
Thank you Ell for your quick answer.
When I read your explanation, I have a feeling that I understand. But when I try to apply this, I get nothing. I tried with an alpha channel, a layer mask, a selection mask (where I can edit transparency) without any result in the image.
Please, give me an example applying this damned Alpha percentile. I am sure that I will understand with an example.
The example shows an image with transparency, blurred using Median Blur, with a radius of 10, and different alpha percentiles:
https://i.imgur.com/vBQgA7D.png
Note that there is no selection or mask involved.
Hope this helps :)
-- Ell
median blur filter
That's OK now!
It was so simple :-s
Thank you very much.
Julien
Le 31/10/2018 à 08:23, Ell via gimp-docs-list a écrit :
On 10/31/18 2:45 AM, Julien Hardelin wrote:
Thank you Ell for your quick answer.
When I read your explanation, I have a feeling that I understand. But when I try to apply this, I get nothing. I tried with an alpha channel, a layer mask, a selection mask (where I can edit transparency) without any result in the image.
Please, give me an example applying this damned Alpha percentile. I am sure that I will understand with an example.
The example shows an image with transparency, blurred using Median Blur, with a radius of 10, and different alpha percentiles:
https://i.imgur.com/vBQgA7D.png
Note that there is no selection or mask involved.
Hope this helps :)
-- Ell
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