path: root/doc/chalk/using-filters.docbook

<chapter id="filters">
<title>Filters</title>

<para>
&chalk; comes with a number of filters. These can be used to enhance or
otherwise modify the image, either in whole or in part. Some filters are
applied directly, others are customizable, meaning that you are presented with
a dialog in which you can tune the result to your liking before the filter is
applied. If a selection is active, a filter is applied on the selected part of
the image. If no selection is active, the entire image is modified.
</para><para>
This chapter describes the available filters in detail. To make comparing the
filters easier, each filter has been applied to the same image and each description
contains a comparison image, showing the result of applying the filter described.
The original image (with thanks to the photographer, Christian Peper) is shown
below at half the original size. The sample images demonstrating the
results of applying the filters, with the original image at the left and the
modified image at the right, are shown at 25% of the original size.
</para>
<note><para>Some filters yield reasonable results for most images. For
other filters though, quite some tweaking needs to be done before the desired
outcome is achieved. If a filter does not do what you want, it might need
more or less customising. The examples in this chapter are exaggerated to
give a good impression of the filters. You will usually want to have more
<quote>gentle</quote> modifications.</para></note>
<para>
Tip: If you want to apply a filter to everything except a certain part of your
image (for example, you want to desaturate your image except for the centre),
select the part you do not want to apply the filter to, use the
<menuchoice><guimenu>Select</guimenu><guimenuitem>Invert</guimenuitem></menuchoice>
menu option, and then apply the filter.
</para>
<para>
See the <link linkend="commands-dialogs-filters">Dialogs for working with
filters</link> section for descriptions of the settings available for the
customizable filters.
</para>

<screenshot>
<screeninfo>The original image</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The original image</phrase>
</textobject>
<caption><para>The original image</para></caption>
</mediaobject>
</screenshot>

<sect1 id="filters-autocontrast">
<title>The Auto Contrast filter</title>
<para>
The Auto Contrast filter changes the contrast of your image to what should be
the best settings. Usually this works out fine, but in some cases (for example
photos taken under unusual lighting circumstances), the filter will not yield
satisfying results.
</para>
<para>
You can find the Auto Contrast filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Adjust</guisubmenu></menuchoice> menu. This filter is not customizable.
</para>
<screenshot>
<screeninfo>The image with the Auto Contrast filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-autocontrast.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Auto Contrast filter applied to it</phrase>
</textobject>
<caption><para>The image with the Auto Contrast filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-blur">
<title>The Blur filter</title>
<para>
You can use the Blur filter to blur your image (give it a fuzzy look).
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Blur</guisubmenu></menuchoice> menu.
See the section on <link linkend="commands-dialogs-filters-blur">the
<guilabel>Blur</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Blur filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-blur.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Blur filter applied to it</phrase>
</textobject>
<caption><para>The image with the Blur filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-brightnesscontrast">
<title>The Brightness / Contrast filter</title>
<para>
With this filter, you can adjust the brightness and contrast of your image.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Adjust</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-brightnesscontrast">the
<guilabel>Brightness / Contrast</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Brightness / Contrast filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-brightnesscontrast.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Brightness / Contrast filter applied to it</phrase>
</textobject>
<caption><para>The image with the Brightness / Contrast filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-bumpmap">
<title>The Bumpmap filter</title>
<para>
The Bumpmap filter takes two layers and uses one of these to convert the other
one so that it will give an illusion of depth. The object layer (the layer to be
transformed) is the actual layer that should receive the three-dimensional
looks. The bumpmap layer is a grayscale layer, which is read and used to
determine the height for each point of the object layer.  Alternatively, the
same layer can be used as both object layer and bumpmap layer.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Map</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-bumpmap">the
<guilabel>Bumpmap</guilabel> dialog</link> for more information on its
settings.
</para>
<screenshot>
<screeninfo>The image with the Bumpmap filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-bumpmap.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Bumpmap filter applied to it</phrase>
</textobject>
<caption><para>The image with the Bumpmap filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-cimg">
<title>The CImg Image Restoration filter</title>
<para>
With this filter, you can perform minor enhancements to your image, for
example removing small scratches or adding a slight blur. The difference
between our sample original image and the result of applying this filter with
standard settings is virtually none.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Enhance</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-imagerestoration">the
<guilabel>Image Restoration</guilabel> dialog</link>
for more information on its settings.
</para>
</sect1>

<sect1 id="filters-coloradjustment">
<title>The Color Adjustment filter</title>
<para>
This filter allows you to change the looks of your image by increasing or
decreasing the abundance of certain colors.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Adjust</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-coloradjustment">the
<guilabel>Color Adjustment</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Color Adjustment filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-coloradjustment.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Color Adjustment filter applied to it</phrase>
</textobject>
<caption><para>The image with the Color Adjustment filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-colortoalpha">
<title>The Color to Alpha filter</title>
<para>
This filter changes a color or color range in your image to become
transparent, effectively clearing regions with those colors.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Colors</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-colortoalpha">the
<guilabel>Color to Alpha</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Color to Alpha filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-colortoalpha.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Color to Alpha filter applied to it</phrase>
</textobject>
<caption><para>The image with the Color to Alpha filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-colortransfer">
<title>The Color Transfer filter</title>
<para>
With this filter, you can re-color an image using the colors from another
image. Each color in your current image will be replaced by the most alike
color used in the other image.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Colors</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-colortransfer">the
<guilabel>Color Transfer</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Color Transfer filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-colortransfer.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Color Transfer filter applied to it</phrase>
</textobject>
<caption><para>The image with the Color Transfer filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-customconvolution">
<title>The Custom Convolution filter</title>
<para>
This filter allows you to distort your image by setting a number of
parameters.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Enhance</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-customconvolution">the
<guilabel>Custom Convolution</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Custom Convolution filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-customconvolution.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Custom Convolution filter applied to it</phrase>
</textobject>
<caption><para>The image with the Custom Convolution filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-desaturate">
<title>The Desaturate filter</title>
<para>
This filter converts your image to grayscale by setting the saturation of each
pixel's color to zero.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Adjust</guisubmenu></menuchoice> menu. 
This filter is not customizable.
</para>
<screenshot>
<screeninfo>The image with the Desaturate filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-desaturate.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Desaturate filter applied to it</phrase>
</textobject>
<caption><para>The image with the Desaturate filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-edgedetection">
<title>The Edge Detection filters</title>
<para>
These filters try to detect <quote>edges</quote> (boundaries) in the picture
and modify the image such that only these edges retain their respective colors,
while the rest of the image is turned gray. Through the use of lighting the
image will then get a three-dimensional look.
</para><para>
There are four edge detection filters available. Each of these detects edges
from a different side (possibly considering other parts of the image as being
edges) and will therefore obtain a different resulting image.
</para>
<para>
You can find the filters in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Edge Detection</guisubmenu></menuchoice> menu. 
These filters are not customizable.
</para>
<screenshot>
<screeninfo>The image with the Bottom Edge Detection filter applied to
it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-edgebottom.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Bottom Edge Detection filter applied to it</phrase>
</textobject>
<caption><para>The image with the Bottom Edge Detection filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-emboss">
<title>The Emboss filters</title>
<para>
Emboss filters work somewhat like edge detection filters, with the difference
that embossed images are entirely gray. Areas in the picture are detected and
are given a certain <quote>height level</quote>, which is made visible by using
grayscale borders, making the image look like it is three-dimensional.
</para>
<para>
You can find the filters in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Emboss</guisubmenu></menuchoice> menu. 
Except for the Emboss with Variable Depth filter, these filters are not
customizable. See the section on <link
linkend="commands-dialogs-filters-emboss">the
<guilabel>Emboss</guilabel> dialog</link>
for more information on the settings of the Emboss with Variable Depth filter.
</para>
<screenshot>
<screeninfo>The image with the Emboss in All Directions filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-embossall.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Emboss in All Directions filter applied to it</phrase>
</textobject>
<caption><para>The image with the Emboss in All Directions filter applied to
it</para></caption>
</mediaobject>
</screenshot>
<screenshot>
<screeninfo>The image with the Emboss with Variable depth filter applied to
it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-embossvariable.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Emboss with Variable depth filter applied to it</phrase>
</textobject>
<caption><para>The image with the Emboss with Variable depth filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-gaussianblur">
<title>The Gaussian Blur filter</title>
<para>
This filter makes the image a little fuzzy by blurring it in a pseudo-random
way. A gaussian algorithm is used for finding the extent to which each part of
the image should be blurred.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Blur</guisubmenu></menuchoice> menu. 
This filter is not customizable.
</para>
<screenshot>
<screeninfo>The image with the Gaussian Blur filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-gaussianblur.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Gaussian Blur filter applied to it</phrase>
</textobject>
<caption><para>The image with the Gaussian Blur filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-gaussiannoise">
<title>The Gaussian Noise Reduction filter</title>
<para>
With this filter, you can remove noise from your image.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Enhance</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-gaussiannoise">the
<guilabel>Gaussian Noise Reduction</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Gaussian Noise Reduction filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-gaussiannoise.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Gaussian Noise Reduction filter applied to it</phrase>
</textobject>
<caption><para>The image with the Gaussian Noise Reduction filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-invert">
<title>The Invert filter</title>
<para>
This filter inverts all colors. The Red, Green and Blue component of each pixel
are taken and subtracted from 255. This means that red becomes cyan, green
becomes purple, and blue becomes yellow. The resulting values form the new
pixel color.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Adjust</guisubmenu></menuchoice> menu. 
This filter is not customizable.
</para>
<screenshot>
<screeninfo>The image with the Invert filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-invert.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Invert filter applied to it</phrase>
</textobject>
<caption><para>The image with the Invert filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-lenscorrection">
<title>The Lens Correction filter</title>
<para>
This filter can fix distortions in your image resulting from for example
<quote>pincushion</quote> lens effects, and modify some lighting.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Other</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-lenscorrection">the
<guilabel>Lens Correction</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Lens Correction filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-lenscorrection.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Lens Correction filter applied to it</phrase>
</textobject>
<caption><para>The image with the Lens Correction filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-maximizechannel">
<title>The Maximize Channel filter</title>
<para>
This filter gives each pixel in your image a new color: only the color channel
that contributes the most to the color of a pixel is retained (except for
gray pixels, which are kept gray).
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Colors</guisubmenu></menuchoice> menu. 
This filter is not customizable.
</para>
<screenshot>
<screeninfo>The image with the Maximize Channel filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-maximizechannel.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Maximize Channel filter applied to it</phrase>
</textobject>
<caption><para>The image with the Maximize Channel filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-meanremoval">
<title>The Mean Removal filter</title>
<para>
This filter sharpens the image by changing the colors of neighboring pixels
with approximately the same color, so that small differences are evened out.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Enhance</guisubmenu></menuchoice> menu. 
This filter is not customizable.
</para>
<screenshot>
<screeninfo>The image with the Mean Removal filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-meanremoval.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Mean Removal filter applied to it</phrase>
</textobject>
<caption><para>The image with the Mean Removal filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-minimizechannel">
<title>The Minimize Channel filter</title>
<para>
This filter gives each pixel in your image a new color: the color channel
that contributes the most to the color of a pixel is removed (except for
gray pixels, which are kept gray).
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Colors</guisubmenu></menuchoice> menu. 
This filter is not customizable.
</para>
<screenshot>
<screeninfo>The image with the Minimize Channel filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-minimizechannel.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Minimize Channel filter applied to it</phrase>
</textobject>
<caption><para>The image with the Minimize Channel filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-oilpaint">
<title>The Oilpaint filter</title>
<para>
An oilpaint effect is given to the image by creating patch-shaped areas in which
the most important color is applied to the entire area.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Artistic</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-oilpaint">the
<guilabel>Oilpaint</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Oilpaint filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-oilpaint.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Oilpaint filter applied to it</phrase>
</textobject>
<caption><para>The image with the Oilpaint filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-pixelize">
<title>The Pixelize filter</title>
<para>
The image is pixelated by taking a square area and giving it the mean color
value of the pixels it contains.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Artistic</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-pixelize">the
<guilabel>Pixelize</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Pixelize filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-pixelize.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Pixelize filter applied to it</phrase>
</textobject>
<caption><para>The image with the Pixelize filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-raindrops">
<title>The Raindrops filter</title>
<para>
This filter makes it look like raindrops have fallen on the image by distorting
drop-shaped areas with a lens-like effect as one would see when looking
at the image through a real raindrop. Some raindrops will have a fish-eye lens
effect.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Artistic</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-raindrops">the
<guilabel>Raindrops</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Raindrops filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-raindrops.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Raindrops filter applied to it</phrase>
</textobject>
<caption><para>The image with the Raindrops filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-randomnoise">
<title>The Random Noise filter</title>
<para>
With this filter, random noise can be added to your image.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Other</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-randomnoise">the
<guilabel>Random Noise</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Random Noise filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-randomnoise.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Random Noise filter applied to it</phrase>
</textobject>
<caption><para>The image with the Random Noise filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-randompick">
<title>The Random Pick filter</title>
<para>
This filter distorts the image by interchanging pixels.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Other</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-randompick">the
<guilabel>Random Pick</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Random Pick filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-randompick.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Random Pick filter applied to it</phrase>
</textobject>
<caption><para>The image with the Random Pick filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-roundcorners">
<title>The Round Corners filter</title>
<para>
This filter just rounds off the corners of the image. This is done by making
the outside of the rounded corner transparent.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Map</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-roundcorners">the
<guilabel>Round Corners</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Round Corners filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-roundcorners.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Round Corners filter applied to it</phrase>
</textobject>
<caption><para>The image with the Round Corners filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-sharpen">
<title>The Sharpen filter</title>
<para>
This filter sharpens the image.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Enhance</guisubmenu></menuchoice> menu. 
This filter is not customizable.
</para>
<screenshot>
<screeninfo>The image with the Sharpen filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-sharpen.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Sharpen filter applied to it</phrase>
</textobject>
<caption><para>The image with the Sharpen filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-smalltiles">
<title>The Small Tiles filter</title>
<para>
The picture is reduced in size and repeated multiple times.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Map</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-smalltiles">the
<guilabel>Small Tiles</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Small Tiles filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-smalltiles.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Small Tiles filter applied to it</phrase>
</textobject>
<caption><para>The image with the Small Tiles filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-sobel">
<title>The Sobel filter</title>
<para>
This is a more enhanced edge detection filter.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Edge Detection</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-sobel">the
<guilabel>Sobel</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Sobel filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-sobel.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Sobel filter applied to it</phrase>
</textobject>
<caption><para>The image with the Sobel filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-unsharpmask">
<title>The Unsharp Mask filter</title>
<para>
This filter sharpens part of your image. (The name <quote>unsharp</quote> is
historical: parts would be masked off while the rest would be made less sharp.)
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Enhance</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-unsharpmask">the
<guilabel>Unsharp Mask</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Unsharp Mask filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-unsharpmask.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Unsharp Mask filter applied to it</phrase>
</textobject>
<caption><para>The image with the Unsharp Mask filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-wave">
<title>The Wave filter</title>
<para>
This filter transforms your image into a wave shape.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Other</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-wave">the
<guilabel>Wave</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Wave filter applied to it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-wave.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Wave filter applied to it</phrase>
</textobject>
<caption><para>The image with the Wave filter applied to it</para></caption>
</mediaobject>
</screenshot>
</sect1>

<sect1 id="filters-waveletnoise">
<title>The Wavelet Noise Reduction filter</title>
<para>
This filter reduces noise in the image by giving loose pixels a color close to
the surrounding area. This causes small details to be lost, but can enhance the
general view of the image when this is hampered by too many unnecessary details.
</para>
<para>
You can find the filter in the <menuchoice><guimenu>Filter</guimenu>
<guisubmenu>Enhance</guisubmenu></menuchoice> menu. 
See the section on <link
linkend="commands-dialogs-filters-waveletnoise">the
<guilabel>Wavelet Noise Reduction</guilabel> dialog</link>
for more information on its settings.
</para>
<screenshot>
<screeninfo>The image with the Wavelet Noise Reduction filter applied to
it</screeninfo>
<mediaobject>
<imageobject>
<imagedata fileref="crocusses-waveletnoise.png" format="PNG" />
</imageobject>
<textobject>
<phrase>The image with the Wavelet Noise Reduction filter applied to it</phrase>
</textobject>
<caption><para>The image with the Wavelet Noise Reduction filter applied to
it</para></caption>
</mediaobject>
</screenshot>
</sect1>


</chapter>