PanoTools Anti Aliasing Filters - Revision history

Erik Krause: wordsmithing

2008-11-01T21:10:07Z

wordsmithing

Erik Krause: Prepared for new glossary template

2007-11-18T15:36:12Z

Prepared for new glossary template

Erik Krause: typo

2007-11-17T23:37:43Z

typo

Thomas Rauscher: added comment

2007-11-12T13:40:51Z

added comment

Thomas Rauscher: added examples page

2007-11-11T15:26:04Z

added examples page

Thomas Rauscher: Pano12 Anti Aliasing Filters moved to PanoTools Anti Aliasing Filters: its not only pano12...

2007-11-11T15:14:28Z

Pano12 Anti Aliasing Filters moved to PanoTools Anti Aliasing Filters: its not only pano12...

Thomas Rauscher: initial version

2007-11-11T15:13:48Z

initial version

New page

Since version 2.7.10 the [[PanoTools]] library contains several [[interpolation]] filter that avoid [[aliasing]]. Those filters use a dynamic kernel size where the size of the filter kernel is calculated for each pixel.

There are two theoretical types of kernels that have an equal right for existence. Kernels based on the [[wikipedia:Normal distribution|Gaussian distribution]] and kernels based on the [[wikipedia:Sinc function|Sinc function]]. Both kernels have an infinite width so a windowing function is used to limit the kernel size for practical reasons. Gaussian based kernels do not contain negative values, sinc based do.

The values in the plot describe the contribution of a pixel depending on the distance from the center. A wider kernel in the center means a more blurry image but if it is to narrow it tends to produce aliasing. If the kernel contains negative values the images also gets sharpened. Some examples: If you look at the plots you can see that a ''Hamming Filter'' produces blurrier image then the ''Blackmann Filter''. The ''Lanczos2 Filter'' introduces more sharpening then the ''Mitchell Filter'' because of the larger negative areas.

{| class="wikitable"
|-
! short
! ID
! Name
! f(x)
! Kernel size
|-
| aabox || 8 || Box Filter || [[Image:plot_s_filter_8.png]] || 0.5
|-
| aatriangle || 9 || Bartlett/Triangle Filter || [[Image:plot_s_filter_9.png]] || 1.0
|-
| aahermite || 10 || Hermite Filter || [[Image:plot_s_filter_10.png]] || 1.0
|-
| aahanning || 11 || Hanning Filter || [[Image:plot_s_filter_11.png]] || 1.0
|-
| aahamming || 12 || Hamming Filter || [[Image:plot_s_filter_12.png]] || 1.0
|-
| aablackman || 13 || Blackmann Filter || [[Image:plot_s_filter_13.png]] || 1.0
|-
| aagaussian || 14 || Gaussian 1/sqrt(2) Filter (blury) || [[Image:plot_s_filter_14.png]] || 1.25
|-
| aagaussian2 || 15 || Gaussian 1/2 Filter (sharper) || [[Image:plot_s_filter_15.png]] || 1.0
|-
| aaquadratic || 16 || Quadardic Filter || [[Image:plot_s_filter_16.png]] || 1.5
|-
| aacubic || 17 || Cubic Filter || [[Image:plot_s_filter_17.png]] || 2.0
|-
| aacatrom || 18 || Catmull-Rom Filter || [[Image:plot_s_filter_18.png]] || 2.0
|-
| aamitchell || 19 || Mitchell Filter || [[Image:plot_s_filter_19.png]] || 2.0
|-
| aalanczos2 || 20 || Lanczos2 Filter || [[Image:plot_s_filter_20.png]] || 2.0
|-
| aalanczos3 || 21 || Lanczos3 Filter || [[Image:plot_s_filter_21.png]] || 3.0
|-
| aablackmanbessel || 22 || Blackman/Bessel Filter || [[Image:plot_s_filter_22.png]] || 3.2383
|-
| aablackmansinc || 23 || Blackman/sinc Filter || [[Image:plot_s_filter_23.png]] || 4.0
|}

[[Category:Glossary]]

@@ Line 1: / Line 1: @@
-{{Glossary|Since version 2.7.10 the [[PanoTools]] library contains several [[interpolation]] filter that avoid [[aliasing]].|1}} Those filters use a dynamic kernel size where the size of the filter kernel is calculated for each pixel.
+{{Glossary|Since version 2.7.10 the [[PanoTools]] library contains several [[interpolation]] filters that avoid [[aliasing]].|1}} Those filters use a dynamic kernel size where the size of the filter kernel is calculated for each pixel. The kernel size in the table refers to the kernel used if there is no resizing (f.e. rotation only). If image size is reduced a larger kernel is needed which increases execution times.
-There are two theoretical types of kernels that have an equal right for existence. Kernels based on the [[wikipedia:Normal distribution|Gaussian distribution]] and kernels based on the [[wikipedia:Sinc function|Sinc function]]. Both kernels have an infinite width so a windowing function is used to limit the kernel size for practical reasons. Gaussian based kernels do not contain negative values, sinc based do.
+There are two types of kernels with equal right to exist. Non-sharpening kernels (ID 8 to 17) based on the [[wikipedia:Normal distribution|Gaussian distribution]] and sharpening kernels (ID 18 to 23) based on the [[wikipedia:Sinc function|Sinc function]]. Both kernel types have an infinite width so a windowing function is used to limit the kernel size for practical reasons. Gaussian based kernels do not contain negative values, sinc based do.
-The values in the plot describe the contribution of a pixel depending on the distance from the center. A wider kernel in the center means a more blurry image but if it is to narrow it tends to produce aliasing. If the kernel contains negative values the images also gets sharpened. Some examples: If you look at the plots you can see that a ''Hamming Filter'' produces blurrier image then the ''Blackmann Filter''. The ''Lanczos2 Filter'' introduces more sharpening then the ''Mitchell Filter'' because of the larger negative areas.
+The values in the plot describe the contribution of a pixel depending on the distance from the center. A wider kernel in the center means a more blurry image but if it is too narrow it tends to produce aliasing. If the kernel contains negative values the images also gets sharpened. Some examples: If you look at the plots you can see that a ''Hamming Filter'' produces blurrier image then the ''Blackmann Filter''. The ''Lanczos2 Filter'' introduces more sharpening then the ''Mitchell Filter'' because of the larger negative areas.
 {| class="wikitable"

← Older revision		Revision as of 15:36, 18 November 2007
Line 1:		Line 1:
−	Since version 2.7.10 the [[PanoTools]] library contains several [[interpolation]] filter that avoid [[aliasing]]. Those filters use a dynamic kernel size where the size of the filter kernel is calculated for each pixel.	+	{{Glossary\|Since version 2.7.10 the [[PanoTools]] library contains several [[interpolation]] filter that avoid [[aliasing]].\|1}} Those filters use a dynamic kernel size where the size of the filter kernel is calculated for each pixel.

	There are two theoretical types of kernels that have an equal right for existence. Kernels based on the [[wikipedia:Normal distribution\|Gaussian distribution]] and kernels based on the [[wikipedia:Sinc function\|Sinc function]]. Both kernels have an infinite width so a windowing function is used to limit the kernel size for practical reasons. Gaussian based kernels do not contain negative values, sinc based do.		There are two theoretical types of kernels that have an equal right for existence. Kernels based on the [[wikipedia:Normal distribution\|Gaussian distribution]] and kernels based on the [[wikipedia:Sinc function\|Sinc function]]. Both kernels have an infinite width so a windowing function is used to limit the kernel size for practical reasons. Gaussian based kernels do not contain negative values, sinc based do.

@@ Line 30: / Line 30: @@
 | aagaussian2 || 15 || Gaussian 1/2 Filter (sharper) || [[Image:plot_s_filter_15.png]] || 1.0
 |-
-| aaquadratic || 16 || Quadardic Filter || [[Image:plot_s_filter_16.png]] || 1.5
+| aaquadratic || 16 || Quadratic Filter || [[Image:plot_s_filter_16.png]] || 1.5
 |-
 | aacubic || 17 || Cubic Filter || [[Image:plot_s_filter_17.png]] || 2.0 || default filter in [[Photoshop]]

@@ Line 11: / Line 11: @@
 ! Name
 ! f(x)
-! Kernel size
+! Kernel size<br>(radius)
 |-
-| aabox || 8 || Box Filter || [[Image:plot_s_filter_8.png]] || 0.5
+| aabox || 8 || Box Filter || [[Image:plot_s_filter_8.png]] || 0.5 || sometimes called ''nearest neighbor''
 |-
-| aatriangle || 9 || Bartlett/Triangle Filter || [[Image:plot_s_filter_9.png]] || 1.0
+| aatriangle || 9 || Bartlett/Triangle Filter || [[Image:plot_s_filter_9.png]] || 1.0 || sometimes called ''bilinear''
 |-
 | aahermite || 10 || Hermite Filter || [[Image:plot_s_filter_10.png]] || 1.0
@@ Line 31: / Line 32: @@
 | aaquadratic || 16 || Quadardic Filter || [[Image:plot_s_filter_16.png]] || 1.5
 |-
-| aacubic || 17 || Cubic Filter || [[Image:plot_s_filter_17.png]] || 2.0
+| aacubic || 17 || Cubic Filter || [[Image:plot_s_filter_17.png]] || 2.0 || default filter in [[Photoshop]]
 |-
 | aacatrom || 18 || Catmull-Rom Filter || [[Image:plot_s_filter_18.png]] || 2.0

@@ Line 45: / Line 45: @@
 | aablackmansinc || 23 || Blackman/sinc Filter || [[Image:plot_s_filter_23.png]] || 4.0
 |}
 [[Category:Glossary]]