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diff --git a/doc/chalk/using-selections.docbook b/doc/chalk/using-selections.docbook new file mode 100644 index 00000000..675088ec --- /dev/null +++ b/doc/chalk/using-selections.docbook @@ -0,0 +1,200 @@ +<chapter id="selections"> +<title>Selections</title> + +<para> +This chapter gives a short introduction on selections. +</para><para> +You can select a part of an image masking off the rest. This is handy when +you want to cut, copy or just modify a part of the image without affecting +the rest. For processing selected objects &chalk; applies a mask. Each pixel of +the selection is processed based on a value of its mask, or the <quote>level +of the selection</quote>, that can range from 0 (unselected) to 255 +(selected). Yes, that is right, you can have fractionally selected pixels. +And by working on individual pixels you can <quote>paint</quote> your selection. +</para><para> +The selection mask is visualized with unselected pixels having a blueish +tint, and selected pixels looking like normal. Fractionally selected pixels +are shown as something in between. Additionally a red border is drawn around +the selected areas. Fractionally selected pixels are inside the border, so +even inside the red border you can possibly see the blueish tint on some pixels. +</para> + +<sect1 id="selections-making"> +<title>Making a selection</title> +<para> +A whole range of tools exist to make selections. From rectangles, ellipses +and freehand to the more exotic like color range select. When you make +several selections they add up. So a rectangle select followed by an +ellipse select select both areas. Later on, you can subtract areas from +the selection by using, for example, the <guilabel>Erase Selection</guilabel> tool. +</para><para> +To get back to normal (no active selection), choose +<menuchoice><guimenu>Select</guimenu><guimenuitem>Deselect</guimenuitem> +</menuchoice>. To select all pixels, choose +<menuchoice><guimenu>Select</guimenu><guimenuitem>Select All</guimenuitem> +</menuchoice>. +</para><para> +You may think that those two actions give the same result, but it +is much more efficient to have no active selection than to have selected +everything. +</para><para> +After having deselected you can bring your selection back by choosing +<menuchoice><guimenu>Select</guimenu><guimenuitem>Reselect</guimenuitem> +</menuchoice>. +</para> +</sect1> + +<sect1 id="selections-painting"> +<title>Painting your selection</title> +<para> +As said above you can essentially paint your selection, and just like +when you paint normally you can choose to paint your selection freehand or +guided with rectangles, ellipses, &etc;. You also have the choice of different +paint tools like pen, brush, airbrush, &etc;. Choose the guide tool, and the +paint tool in the toolbox, and go ahead and <quote>paint</quote> your +selection. +</para><para> +The guide tools work just like you may be used to from other applications. So +holding down shift while drawing a rectangle or an ellipse still forces them to +be a square or a circle respectively. +</para> + +<screenshot> +<screeninfo>Painting a selection</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="using-selections-1.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>Painting a selection</phrase> +</textobject> +<caption><para>Painting a selection</para></caption> +</mediaobject> +</screenshot> +<screenshot> +<screeninfo>Painting a selection</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="using-selections-2.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>Painting a selection</phrase> +</textobject> +<caption><para>Painting a selection</para></caption> +</mediaobject> +</screenshot> + +</sect1> + +<sect1 id="selections-unselecting"> +<title>Unselecting</title> +<para> +All the selection paint tools have an option to add or subtract from the +selection. This means that you can use all your familiar tools to both select +and unselect. There is also a true selection eraser among the selection paint +tools. +</para> + +<screenshot> +<screeninfo>Unselecting</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="using-selections-3.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>Unselecting</phrase> +</textobject> +<caption><para>Unselecting</para></caption> +</mediaobject> +</screenshot> +</sect1> + +<sect1 id="selections-making-new"> +<title>Making a new selection</title> +<para> +When you want to make a new selection, replacing the currently active one, you +first need to deselect the active selection. Choose +<menuchoice><guimenu>Select</guimenu><guimenuitem>Deselect</guimenuitem> +</menuchoice>. +</para> +</sect1> + +<sect1 id="selections-contigious"> +<title>Selecting a contiguous area (magic wand)</title> +<para> +To follow the analogy of painting your selection &chalk; also provides an +equivalent to filling a contiguous area. Some paint applications call this +selection tool the magic wand tool. What it does is select the nearby +pixels as long as they have nearly the same color as the pixel you click +on. The selection floods out from the point you click on. In the fuzziness +option you can set how different the colors are allowed to be before the +flooding stops. +</para> + +<screenshot> +<screeninfo>Before the magic wand</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="using-selections-4.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>Before the magic wand</phrase> +</textobject> +<caption><para>Before the magic wand</para></caption> +</mediaobject> +</screenshot> + +<screenshot> +<screeninfo>A magic wand selection</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="using-selections-5.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>A magic wand selection</phrase> +</textobject> +<caption><para>A magic wand selection</para></caption> +</mediaobject> +</screenshot> + +</sect1> + +<sect1 id="selections-similar"> +<title>Selecting similar colors</title> +<para> +The <guilabel>Select Similar</guilabel> tool lets you pick a pixel and then select all pixels that +have a similar color. Picking a color in one corner of the image may select a +pixel in another corner if they have similar color. +With the <guilabel>Fuzziness</guilabel> option you can set how similar the colors must be to become +selected. +</para> + +<screenshot> +<screeninfo>Selecting similar colors</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="using-selections-6.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>Selecting similar colors</phrase> +</textobject> +<caption><para>Selecting similar colors</para></caption> +</mediaobject> +</screenshot> +</sect1> + +<sect1 id="selections-inverting"> +<title>Inverting the selection</title> +<para> +In some cases it is easier to specify your selection the other way around. That +is, first you select the parts that ultimately should not be selected and then +then you choose +<menuchoice><guimenu>Select</guimenu><guimenuitem>Invert</guimenuitem> +</menuchoice>. +What invert does, is that for every pixel it flips the selection level so to +speak, by setting it to 256 minus the current selection level. Thus what was +selected becomes unselected and vice versa. +</para> +</sect1> + +</chapter> |