mirror of https://github.com/GNOME/gimp.git
460 lines
7.9 KiB
HTML
460 lines
7.9 KiB
HTML
<HTML
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><HEAD
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><TITLE
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>Convert to Indexed </TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.49"><LINK
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REL="HOME"
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TITLE="GIMP User Manual"
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HREF="../contents.html"><LINK
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REL="UP"
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TITLE="Image"
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HREF="../image/index.html"><LINK
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REL="PREVIOUS"
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TITLE="Convert to Grayscale"
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HREF="../image/image/mode/convert_to_grayscale.html"><LINK
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REL="NEXT"
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TITLE="Desaturate"
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HREF="../image/image/colors/desaturate.html"></HEAD
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><BODY
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CLASS="SECT1"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>GIMP User Manual</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="../image/image/mode/convert_to_grayscale.html"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 4. Image</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="../image/image/colors/desaturate.html"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECT1"
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><H1
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CLASS="SECT1"
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><A
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NAME="DIALOGS-CONVERT-TO-INDEXED"
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><SPAN
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CLASS="INTERFACE"
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>Convert to Indexed</SPAN
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></A
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></H1
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><A
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NAME="AEN1310"
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></A
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><A
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NAME="AEN1312"
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></A
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><P
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> This mode enables you to convert <SPAN
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CLASS="ACRONYM"
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>RGB</SPAN
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> or grayscale images
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to indexed images. An indexed image is an image which only has the colors
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specified in its color palette. The color palette is saved in the image
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file. The maximum number of colors in an indexed image is 256. If you want
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to make transparent <SPAN
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CLASS="ACRONYM"
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>GIF</SPAN
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> images, then you can only use a
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maximum of 255 colors since the last color will be used to determine if the
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pixel is opaque or transparent.
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</P
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="PALETTEOPTIONS"
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>Palette Options</A
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></H2
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><P
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></P
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><DL
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><DT
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><SPAN
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CLASS="GUILABEL"
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>Generate optimal palette</SPAN
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></DT
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><DD
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><P
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> For the most part, this option is the best to use when
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creating an indexed image.
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<SPAN
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CLASS="APPLICATION"
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>GIMP</SPAN
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> will evaluate your colors
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and create a color palette suitable for the image. You can
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specify the number of colors that you want to have in your
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indexed image, but remember that you can't have more than
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255 colors if are about to create an indexed image with
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transparency.
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</P
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></DD
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><DT
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><SPAN
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CLASS="GUILABEL"
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>Use custom palette</SPAN
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></DT
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><DD
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><P
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> If you want to use a predefined palette, you have to use
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this option. You then choose your palette from the drop
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down menu. By default it's <SPAN
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CLASS="GUILABEL"
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>Web
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palette</SPAN
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>. The <SPAN
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CLASS="GUILABEL"
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>Web palette</SPAN
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>
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is the palette used by web browsers such as
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<SPAN
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CLASS="APPLICATION"
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>Netscape</SPAN
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>. This will help you
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create web-safe indexed images.
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<DIV
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CLASS="NOTE"
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><P
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></P
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><TABLE
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CLASS="NOTE"
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WIDTH="90%"
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BORDER="0"
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><TR
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><TD
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WIDTH="25"
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ALIGN="CENTER"
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VALIGN="TOP"
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><IMG
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SRC="../../images/note.gif"
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HSPACE="5"
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ALT="Note"></TD
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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><P
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> There is some debate over indexing against the
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Web palette.
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</P
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></TD
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></TR
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></TABLE
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></DIV
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>
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</P
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></DD
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><DT
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><SPAN
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CLASS="GUILABEL"
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>Custom Palette Options</SPAN
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></DT
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><DD
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><P
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> <SPAN
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CLASS="GUIBUTTON"
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>Remove unused colors from final
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palette</SPAN
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>: If the palette contains colors that
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aren't used in the indexed image, you can remove the extra
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colors and make the image file size smaller. This is a
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good option so keep it enabled.
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</P
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></DD
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><DT
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><SPAN
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CLASS="GUILABEL"
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>Use black/white (1-bit) palette
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</SPAN
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></DT
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><DD
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><P
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> This option will create a monochrome image only built up
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of black and white pixels.
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</P
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></DD
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></DL
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="DITHERING"
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>Dithering</A
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></H2
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><P
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> An indexed image can only be built up of a maximum of 256
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colors. Most of the time this is quite limiting and you will not
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be able to have all the colors in your image represented in this
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limited color space. The image might look like it is built up of
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<SPAN
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CLASS="QUOTE"
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>"bands"</SPAN
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> or <SPAN
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CLASS="QUOTE"
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>"color areas"</SPAN
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>. To make
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indexed images look better, you can dither them. This means that
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two or more colors are mixed to mimic the missing color. The
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disadvantage is that the image can look like it's built up of
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<SPAN
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CLASS="QUOTE"
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>"dots"</SPAN
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>.
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</P
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><P
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> <P
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></P
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><DL
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><DT
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><SPAN
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CLASS="GUILABEL"
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> No color dithering </SPAN
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></DT
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><DD
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><P
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> Will disable dithering completely.
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</P
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></DD
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><DT
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><SPAN
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CLASS="GUILABEL"
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> Positioned color dithering </SPAN
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></DT
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><DD
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><P
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> Use this option when you are dealing with animations
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such as <SPAN
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CLASS="ACRONYM"
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>GIF</SPAN
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> animations. The problem
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with dithering in animations is that the dithering will
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not be constant. If you choose positioned dithering
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instead, the dithering in constant areas will remain
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constant across your frames. It is not as good as
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<SPAN
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CLASS="GUILABEL"
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>Floyd Steinberg dithering</SPAN
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>, but is
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better than no dithering at all.
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</P
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></DD
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><DT
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><SPAN
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CLASS="GUILABEL"
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> Floyd Steinberg color dithering
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(reduced color bleeding) </SPAN
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></DT
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><DD
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><P
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> With normal Floyd Steinberg dithering, you may
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experience too much color bleeding. This is very visible
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when you index gradients, causing an unnatural look. If
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you encounter this effect, it is advisable to use this
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option (i.e Floyd Steinberg dithering reduced colour
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bleeding).
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</P
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></DD
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><DT
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><SPAN
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CLASS="GUILABEL"
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> Floyd Steinberg dithering (normal)
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</SPAN
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></DT
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><DD
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><P
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> This is the best option to use when you are indexing
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images. It's only in special cases that you will use the
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other dithering methods available.
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</P
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></DD
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><DT
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><SPAN
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CLASS="GUILABEL"
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> Enable dithering of transparency
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</SPAN
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></DT
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><DD
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><P
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> Indexed images only have one transparency mode —
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either it is off (the pixel is totally solid) or on (the
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pixel is totally transparent). This makes it very
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difficult to index images with smooth transitions from
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opaque to transparent. When you enable dithering of
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transparency, <SPAN
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CLASS="APPLICATION"
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>GIMP</SPAN
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> will try
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to mimic the smooth transition by dithering pixels on
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and off.
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<DIV
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CLASS="NOTE"
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><P
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></P
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><TABLE
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CLASS="NOTE"
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WIDTH="90%"
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BORDER="0"
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><TR
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><TD
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WIDTH="25"
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ALIGN="CENTER"
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VALIGN="TOP"
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><IMG
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SRC="../../images/note.gif"
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HSPACE="5"
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ALT="Note"></TD
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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><P
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> A good alternative to transparency dithering is the
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<A
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HREF="../filters/semiflatten.html"
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> <SPAN
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CLASS="MOUSEBUTTON"
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>Right</SPAN
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>click >
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<SPAN
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CLASS="GUIMENU"
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>Filters</SPAN
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> >
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<SPAN
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CLASS="GUISUBMENU"
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>Colors</SPAN
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> >
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<SPAN
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CLASS="GUIMENUITEM"
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>Semi-Flatten</SPAN
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> </A
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>
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function.
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</P
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></TD
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></TR
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></TABLE
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></DIV
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>
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</P
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></DD
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></DL
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>
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</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="AEN1390"
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>Additional Information</A
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></H2
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><P
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> Default Keyboard Shortcut: <B
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CLASS="KEYCAP"
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>Alt</B
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>-<B
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CLASS="KEYCAP"
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>I</B
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>
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</P
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></DIV
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></DIV
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
|
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><A
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HREF="../image/image/mode/convert_to_grayscale.html"
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>Prev</A
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></TD
|
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="../contents.html"
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>Home</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><A
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HREF="../image/image/colors/desaturate.html"
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>Next</A
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></TD
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></TR
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><TR
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><TD
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WIDTH="33%"
|
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ALIGN="left"
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VALIGN="top"
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>Convert to Grayscale</TD
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><TD
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WIDTH="34%"
|
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="../image/index.html"
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>Up</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><SPAN
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CLASS="GUIMENUITEM"
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>Desaturate</SPAN
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></TD
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></TR
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></TABLE
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></DIV
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></BODY
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></HTML
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> |