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diff --git a/doc/chalk/using-layers.docbook b/doc/chalk/using-layers.docbook new file mode 100644 index 00000000..3ca80291 --- /dev/null +++ b/doc/chalk/using-layers.docbook @@ -0,0 +1,620 @@ +<chapter id="layers"> +<title>Layers</title> + +<para> +This chapter gives an overview of how layers work in &chalk;. +</para> + +<sect1 id="layers-background"> +<title>Background information on layers</title> + +<para> +Extensive use of &chalk; will almost require you to have some knowledge of +layers. Using layers, you can work on one part of the image without touching +the rest of it, and most effects are best applied on a layer, instead of on +the whole image. Of course, if you do want to apply an effect to an entire +image, &chalk; does offer you that possibility, and there is nothing against +it. +</para><para> +The idea behind layers is quite simple. As the name suggests, layers lie on +top of each other, and together form the layer stack. The final resulting +image is that what you see when looking through the stack from top to bottom. +This means that usually the upper layers of your image will have more or less +transparency, since you cannot look through a layer which has no transparency. +(&chalk; works with opaqueness instead of transparency. A layer that is 100 +percent opaque is 0 percent transparent, and vice versa.) A layer higher in +the stack gets applied later than one lower in the stack. For example, if your +image contains four layers, numbered from 1 (lowest) to 4 (highest), the +effect that layer number 4 adds to the image, is applied to the result from +applying layers 1 through 3. +</para><para> +Every image you edit in &chalk; contains layers. When you create a new image, +the layer box (usually shown at the bottom right of your screen, see <link +linkend="commands-palettes-layers-layers">this section</link>) will contain +one layer. The painting and editing you do is then applied to that layer. Once +you add more layers, you can choose on which part of the image you want to +work, by selecting the respective layer. All further painting is then applied +to that layer, until you select another one. +</para><para> +Layers are also an excellent way to check whether adding certain effects (or +applying certain image modifications) come out right. Add a layer which +contains what you want to try out, and show or hide it with the eye icon in +the layer box. You can especially profit from this method if you have multiple +effects to check out: show and hide them in any combination, and decide which +you like best. And since you can move the layers around, you can also +experiment with the order in which the effects are applied. +</para><para> +See the <link linkend="tutorial-select-layer">Selections and layers +tutorial</link> for a small hands-on introduction. +</para> +</sect1> + +<sect1 id="layers-layerbox"> +<title>The layer box</title> + +<para>The layer box is the instrument you will use most to work with layers. It +gives an overview of the layers that are present in your image, and using it +you can manage layers by adding, removing, reordering or modifying them. +</para><para> +The layer box consists of three parts. The middle part gives an overview of the +layers in the image. At the top, you can set some properties for the current +layer. At the bottom, a couple of layer management options can be found. The +next sections describe these three parts in more detail. +</para> + +<sect2 id="layers-layerbox-overview"> +<title>Layer overview</title> + +<para>This part shows you which layers are present in your image. In a tree-like +structure, the layer group hierarchy is shown: layers that are contained within +a layer group are displayed a bit to the right to indicate their belonging to +that group. +</para><para> +For each layer, a thumbnail preview and its name are shown. The layer name +is preceded by a folder icon if it is a group layer. Furthermore, two +indicators are present: the eye icon shows whether the layer is currently +visible (an open eye indicates that the layer is visible, a closed eye +indicates that it is not), and the lock icon shows whether the layer is +locked. No changes can be made to a locked layer. +</para><para> +When you click on a layer's eye icon, its visibility is switched from on to +off or vice versa. Clicking on the lock icon enables or disables editing of +that layer. You can click on the name of the current layer to rename it. +Note that to rename a layer, it has to be the current one. You do not need to +activate a layer in order to make it (in)visible or (un)locked via the eye and +lock icons, respectively: these work directly. +</para><para> +Doubleclick on a layer entry in the list to open the <link +linkend="commands-dialogs-layers-layerproperties"><guilabel>Layer +Properties</guilabel></link> dialog. This dialog shows a layer's colorspace and +profile. You can also change its name, opacity and composite mode here. +</para> +</sect2> + +<sect2 id="layers-layerbox-options"> +<title>Layer options</title> +<para> +The top of the layer box contains two controls for setting properties of the +currently selected layer. The list box at the left allows you to quickly set +the layer's composite mode. The spin field and slider at the right can be used +to change the layer's opacity. +</para><para> +At the bottom of the layer box, there are five buttons. From left to right, +these are as follows. The <guibutton>New Layer</guibutton> icon brings up a +submenu from which you can choose which type of layer you want to add. This +menu can also be opened by clicking with the &RMB; on the layer box. The +<guibutton>Move Layer Down</guibutton> and <guibutton>Move Layer Up</guibutton> +buttons move the current layer one level down and up, respectively, within the +current layer group. If the layer is already the last or first within the +layer group, trying to move it further will move it out of the layer group. +The <guibutton>Layer Properties</guibutton> button opens the <link +linkend="commands-dialogs-layers-layerproperties"><guilabel>Layer +Properties</guilabel></link> dialog, just as when you would have doubleclicked +on the layer. The <guibutton>Delete Layer</guibutton> button deletes the +current layer. +</para> +</sect2> + +</sect1> + +<sect1 id="layers-working"> +<title>Working with layers</title> + +<para> +Because layers are quite important when extensively using &chalk;, you can +perform a lot of operations on them. These are all available via the <link +linkend="commands-menus-layer"><guimenu>Layer</guimenu> menu</link>. Some of +the possibilities: +</para> + +<variablelist> +<varlistentry><term></term><listitem><para>Add, remove, and duplicate layers;</para></listitem></varlistentry> +<varlistentry><term></term><listitem><para>Create and edit layer masks;</para></listitem></varlistentry> +<varlistentry><term></term><listitem><para>Flip, rotate, scale and shear layers;</para></listitem></varlistentry> +<varlistentry><term></term><listitem><para>Convert layers between colorspaces;</para></listitem></varlistentry> +<varlistentry><term></term><listitem><para>Save layers as images;</para></listitem></varlistentry> +<varlistentry><term></term><listitem><para>View layer histograms.</para></listitem></varlistentry> +</variablelist> + +</sect1> + +<sect1 id="layers-adjustment"> +<title>Adjustment Layers</title> + +<para>Adjustment layers are layers that consist of a filter and an optional +selection. The filter effect is applied to the composite image of all +layers under the adjustment layer in the current layer group. The big +thing is, adjustment layers apply these effects non-destructively. The +original image data is not modified. +</para><para> +Almost all &chalk; filters are suitable for use in adjustment +layers -- even filters that would downgrade the image quality. For instance, +the raindrops filter converts to 8-bit RGB before working its magic. If you +would try to use this filter directly on a 16-bit L*a*b* layer, &chalk; would +warn you about the conversion to RGB and back again this filter would cause. +Not so with adjustment layers: the original data isn't touched, so applying +the filter is safe. +</para><para> +What about the colorspace of an adjustment layer then? In order to examine +this issue, you need to know what happens when &chalk; renders an adjustment +layer. +</para> + +<sect2 id="layers-adjustment-selections"> +<title>Adjustment layers and selections</title> + +<para>If the currently active layer has an active selection, then that selection +will be copied and used as a mask for the adjustment layer. If there is no +active selection, then there will be no mask and the adjustment will apply to +the entire extent of the layers under the adjustment layer in the current +group. There is <emphasis>no</emphasis> way of adding a mask to an existing +adjustment layer. +</para><para> +If there is a mask in the adjustment layer, you can edit the mask using the +ordinary painting tools and painting operations. +</para> + +</sect2> + +<sect2 id="layers-adjustment-projection"> +<title>A note on projections</title> + +<para> +&chalk; composites the layers bottom to top, within each layer group. The +aggregate -- or the projection as it is also called -- is then filtered by +the adjustment layer. If there are layers on top of the adjustment layer, +those are composited onto the projection. &chalk; converts all layer data before +compositing, so if the bottom-most layer in an image is grayscale, all layers +are converted to grayscale before compositing -- and that means that the +adjustment layer projection will be grayscale, too. +</para><para> +With this knowledge you'll understand why &chalk; can often offer better +performance working with layers on top of an adjustment layer which is on top +of a complex layer structure: &chalk; uses the projection and doesn't even look +anymore at the layers under the adjustment layer. Unless, of course, you +change one of them. +</para> +</sect2> + +</sect1> + +<sect1 id="layers-composite"> +<title>Compositing modes</title> + +<para> +Layers can be composited in various ways, each yielding a different effect. +This section describes the available compositing modes. Each description is +accompanied by an example: on top of an original image (see below), a rainbow +gradient is added. +</para> + +<para> +<screenshot> +<screeninfo>The original image</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-original.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The original image</phrase> +</textobject> +<caption><para>The original image</para></caption> +</mediaobject> +</screenshot> +</para> + +<sect2 id="layers-composite-normal"> +<title><guilabel>Normal</guilabel></title> + +<para> +The <guilabel>Normal</guilabel> mode does nothing special. It adds the layer +to the image, and if no other special effects like opacity are changed, the +underlying layers will only be visible at places where the new layer is +itself transparent. +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Normal</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-normal.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Normal</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Normal</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +</sect2> + +<sect2 id="layers-composite-multiply"> +<title><guilabel>Multiply</guilabel></title> + +<para> +The <guilabel>Multiply</guilabel> mode blends the two layers so that the +bottom layer gets <quote>colorized</quote> by the new layer. The resulting +image is generally quite dark. +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Multiply</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-multiply.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Multiply</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Multiply</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +</sect2> + +<sect2 id="layers-composite-burn"> +<title><guilabel>Burn</guilabel>, <guilabel>Dodge</guilabel>, +<guilabel>Divide</guilabel> and <guilabel>Screen</guilabel></title> + +<para> +The <guilabel>Burn</guilabel>, <guilabel>Dodge</guilabel>, +<guilabel>Divide</guilabel> and <guilabel>Screen</guilabel> modes all add an +extra <quote>burning</quote> effect by following contours instead of using +straight lines. In addition, <guilabel>Burn</guilabel> and +<guilabel>Divide</guilabel> use the inverted colors instead of the actual +colors of the composited layer. +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Burn</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-burn.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Burn</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Burn</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Dodge</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-dodge.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Dodge</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Dodge</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Divide</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-divide.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Divide</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Divide</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Screen</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-screen.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Screen</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Screen</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +</sect2> + +<sect2 id="layers-composite-overlay"> +<title><guilabel>Overlay</guilabel></title> + +<para> +Like <guilabel>Multiply</guilabel>, the <guilabel>Overlay</guilabel> mode +colorizes the underlying layer. The resulting image is about as light as +the original layer. +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Overlay</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-overlay.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Overlay</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Overlay</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +</sect2> + +<sect2 id="layers-composite-darken"> +<title><guilabel>Darken</guilabel></title> + +<para> +The <guilabel>Darken</guilabel> mode darkens the underlying layer while +colorizing it to match the colors in the composited layer. +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Darken</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-darken.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Darken</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Darken</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +</sect2> + +<sect2 id="layers-composite-lighten"> +<title><guilabel>Lighten</guilabel></title> + +<para> +The <guilabel>Lighten</guilabel> mode lightens the underlying layer while +colorizing it to match the colors in the composited layer. +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Lighten</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-lighten.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Lighten</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Lighten</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +</sect2> + +<sect2 id="layers-composite-hue"> +<title><guilabel>Hue</guilabel>, <guilabel>Saturation</guilabel> and +<guilabel>Value</guilabel></title> + +<para> +The <guilabel>Hue</guilabel>, <guilabel>Saturation</guilabel> and +<guilabel>Value</guilabel> modes respectively apply the hue, saturation and +value components of the composited layer to the underlying layer. +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Hue</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-hue.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Hue</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Hue</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Saturation</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-saturation.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Saturation</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Saturation</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Value</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-value.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Value</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Value</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +</sect2> + +<sect2 id="layers-composite-color"> +<title><guilabel>Color</guilabel></title> + +<para> +The <guilabel>Color</guilabel> mode colorizes the underlying layer, yielding +very strong colors. +</para> + +<para> +<screenshot> +<screeninfo>The gradient applied with the <guilabel>Color</guilabel> compositing +mode</screeninfo> +<mediaobject> +<imageobject> +<imagedata fileref="mountains-color.png" format="PNG" /> +</imageobject> +<textobject> +<phrase>The gradient applied with the <guilabel>Color</guilabel> compositing +mode</phrase> +</textobject> +<caption><para>The gradient applied with the <guilabel>Color</guilabel> compositing +mode</para></caption> +</mediaobject> +</screenshot> +</para> + +</sect2> + +</sect1> + +<sect1 id="layers-masks"> +<title>Layer Masks</title> + +<para> +Basically, a layer mask is a mask that you place on your paint layer. This +will literally mask areas of the layer, so that the content underneath shows +through. You can paint on it with greyscale colors: the more black the color, +the less the layer under it will shine through, the more white, the less the +layer under it will be shown. So complete white will let nothing through, +complete black will let everything through. Basically, it is a bit like +selecting a piece of your image, and then cutting it, so that the selected +bits go away. So what is the use for a mask here? The big advantage is that it +is non-destructive: if you decide that you masked out the wrong part of your +layer, you can easily remove the mask and start anew, something a lot harder +(not to say near impossible, especially in between sessions) with regular +selection-cutting. +</para><para> +So, how to create a mask? There are 2 ways: +</para> + +<itemizedlist> +<listitem><para> +Start from scratch. +<menuchoice><guimenu>Layer</guimenu><guisubmenu>Mask</guisubmenu><guimenuitem>Create +Mask</guimenuitem></menuchoice>. The mask starts with everything being +retained, that is, a complete white mask. Basically you will not see any +changes as long as you do not paint on it. +</para></listitem> +<listitem><para> +Start from the current selection. +<menuchoice><guimenu>Layer</guimenu><guisubmenu>Mask</guisubmenu><guimenuitem>Mask +From Selection</guimenuitem></menuchoice>. The selectedness will be converted +to whiteness. This means that fully selected area will be visible, fully +unselected areas will be invisible, and the rest will be partially visible, +depending on how much the area was selected. +</para></listitem> +</itemizedlist> + +<sect2 id="layers-masks-editing"> +<title>Editing the mask</title> + +<para> +First, make sure you are editing the mask, not the layer, by making sure +<menuchoice><guimenu>Layer</guimenu><guisubmenu>Mask</guisubmenu><guimenuitem>Edit +Mask</guimenuitem></menuchoice> is checked. (This is checked by default.) Then +you can paint on the layer just like before, only now you are +painting on the mask, instead of on the layer itself. To stop painting on the +mask, you can uncheck the <guilabel>Edit Mask</guilabel> checkbox. There's +also the option to show the mask, through checking +<menuchoice><guimenu>Layer</guimenu><guisubmenu>Mask</guisubmenu><guimenuitem>Show +Mask</guimenuitem></menuchoice>. (This is not checked by +default). This option will render the entire layer as a visual representation +of the mask in greyscale, instead of the actual layer. This can be handy to +see where your mask is, but it might be not as handy when you want to edit it, +since you cannot look at the actual layer. +</para><para> +Other actions: you can also remove the mask if you are not satisfied with it, +and want to start over again, or just want to remove it, with +<menuchoice><guimenu>Layer</guimenu><guisubmenu>Mask</guisubmenu><guimenuitem>Remove +Mask</guimenuitem></menuchoice>. You can also <quote>apply</quote> the mask, +meaning that the mask will be made permanently. This means that the mask is +removed, but that its effect of transparency will be committed to the layer. +</para> + +</sect2> +</sect1> + +</chapter> |