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2. Dialoger relateret til billedstruktur |  |
| 2.2. Dialogen Kanaler | ||
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2. Dialoger relateret til billedstruktur | |
Dialogen Kanaler er den primære måde at redigere, ændre og administrere dine kanaler på. Kanaler har en dobbelt anvendelse. Det er derfor, dialogen er opdelt i to dele: den første del til farvekanaler og den anden del til markeringsmasker.
Farvekanaler gælder for billedet og ikke for et bestemt lag. Grundlæggende er tre primære farver nødvendige for at gengive hele den brede vifte af naturlige farver. Som anden digital software bruger GIMP rød, grøn og blå som primære farver. De første og primære kanaler viser værdierne rød, grøn og blå for hver pixel i billedet.
Ved siden af kanalnavnet er der en miniature, der viser en gråtonerepræsentation af hver kanal, hvor hvid er 100 % og sort er 0 % af den primære farve. Alternativt, hvis dit billede ikke er et farvet billede, men et gråtonebillede, er der kun én primær kanal kaldet Grå. For et indekseret billede med et fast antal kendte farver er der også kun én primær kanal kaldet Indekseret.
Then there is an optional channel called Alpha. This channel displays transparency values of each pixel in your image (See Alpha Channel in Glossary). In front of this channel is a thumbnail displaying a grayscale representation of the transparency where white is opaque and visible, and black is transparent and invisible. If you create your image without transparency then the Alpha channel is not present, but you can add it from the Layers Dialog context menu. Also, if you have more than one layer in your image, GIMP automatically creates an Alpha channel.
![[Bemærk]](images/note.png)
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GIMP understøtter ikke CMYK- og YUV-farvemodeller. |
Figur 15.7. Repræsentation af et billede med kanaler
Rød kanal
Grøn kanal
Blå kanal
Alfakanal
Alle kanaler
Billedet til højre er opdelt i tre farvekanaler (rød, grøn og blå) og alfakanalen for gennemsigtighed. På det højre billede vises gennemsigtigheden som et gråt skakbræt. I farvekanalen er hvid altid hvid, fordi alle farverne er til stede, og sort er sort. Den røde hat er synlig i den røde kanal, men helt usynlig i de andre kanaler. Det samme gælder for grøn og blå, som kun er synlige i deres egne kanaler og usynlige i de andre.
Dialogen kan dokkes. Se hvordan i afsnittet Afsnit 2.3, “Dialoger og dokning”.
Du kan tilgå den:
From the main menu through → → .
From the Tab menu in any dockable dialog by clicking on
and selecting
→ .
In the menu, there is a list of detached windows which exists only if at least one dialog remains open. In this case, you can raise the “Channels” dialog from the main menu: → .
The Channels Dialog consists of a list of color channels and the optional Alpha channel at the top; and below that a list of selection mask channels. A right-click in a channel list entry opens the channel context menu.
The color channels are always organized in the same order. They cannot be removed. You can only change their visibility and select or unselect them. By default, all of these channels are visible and selected.
![[Pas på]](images/caution.png)
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The selected color channels appear highlighted in the dialog. If you click on a color channel in the list you toggle selection of the corresponding channel, meaning a selected channel will become unselected and vice versa. Unselecting one of the color channels red, blue, or green has severe consequences. For instance if you disable the blue channel, all pixels from now on added to the image will not have a blue component, and so a white pixel will have the yellow complementary color. |
GIMP allows you to select multiple selection mask channels and perform actions on them. You can e.g. move them to a different location in the channels stack, and convert them to selections. Selecting multiple channels is done by using the mouse and Shift key, for adding a range of channels, or Ctrl key, for adding or removing the clicked channel.
Directly above the list of selection masks is the header bar. On the left you see the icons that identify the visibility and lock columns. In the middle a text label will tell you how many channels are currently selected if it is more than one.
On the right you see the search entry. Clicking here will allow you to search for and select one or more channels. You will also be able to save this search for future use.
For more details about searching see Search layers and Saved searches.
Hver kanal vises i listen med sine egne egenskaber, som er meget lig lagegenskaber:
Kanalers synlighed
By default, all color channels are visible, and color mask channels are invisible. Clicking on the eye-symbol, or the empty space if the channel is not visible, will toggle the visibility of the channel. Shift-clicking on the icon causes all other channels to be hidden.
Egenskaber for kanallås
Each selection mask channel has lock attributes. If one of its attributes is set, the respective lock icon will show up in front of the thumbnail.
When multiple attributes are set, a double lock icon will show here. Clicking in this column allows you to change these attributes.
Lås pixels
This icon shows when “lock pixels” is enabled for the current channel. When this is enabled, the channel is locked for any action that changes pixels, meaning there will be no changes done to this channel.
Lås placering og størrelse
This icon shows when “lock position and size” is enabled for the current channel. When this is enabled, the channel is locked for any action that changes its position or size.
Lock visibility
This toggle button controls the “Lock” setting for the visibility of the channel. If this is enabled, the channel visibility cannot be changed until you disable the lock.
Et lille forhåndsvisningsikon repræsenterer kanalens effekt. Denne forhåndsvisning kan forstørres ved at holde venstre museknap nede på ikonet.
Navnet på kanalen, som skal være unikt i billedet. Hvis du dobbeltklikker på navnet på en markeringsmaskekanal, kan du redigere det. Navnene på de primære kanaler (rød, grøn, blå, alfa) kan ikke ændres. Hvis du dobbeltklikker på forhåndsvisningsikonet, åbnes en dialog, hvor du kan indstille alle kanalegenskaber.
The button bar at the bottom offers the following functionality:
Ny kanal
This creates a new channel. A dialog will open where you can set the Channel name, the Color tag, the channel attributes and lock attributes, and finally the Opacity and color used for the mask in the image window. A click on the color button displays the GIMP color selector where you can change the mask color.
If you press the Shift key while clicking the button, the New Channel dialog will not be opened. Instead the new channel will be created with the same settings as used previously. This new channel is a selection mask applied over the image. See for more details Selection Mask.
Raise Channels
This moves the selected channels up in the list. Press the Shift key to move the selected channels to the top of the list.
Lower Channels
This moves selected channels down in the list. Press the Shift key to move the selected channels to the bottom of the list.
Duplicate Channels
This creates a copy of the selected channels. The name of the new channels is suffixed with a number.
Replace the Selection with Selected Channels
This transforms the selected channels to become a selection. By default the selection derived from channels replaces the active selection. You can change this by using control keys.
Skift: Markeringen, der stammer fra en kanal, føjes til den aktive markering. Den endelige markering er en sammenlægning af de to.
Ctrl: Den endelige markering er subtraktionen af markeringen, der stammer fra en kanal, fra den aktive markering.
Skift+Ctrl: Den endelige markering er gennemskæringen mellem markeringen fra en kanal og den aktive markering. Kun de markerede dele, der er fælles for begge, bevares.
Delete Channels
This deletes the selected channels.
You can get the Channels context menu by right clicking on a channel. Several of the operations on channels are also available through buttons at the bottom of the channels list. Those operations are documented there.
These commands, except Edit Channel Attributes…, also work when multiple channels are selected.
Kun tilgængelig for markeringsmasker. Her kan du ændre Kanalnavn, Farvemærkat, kanalegenskaber, lås af egenskaber og Udfyldningens uigennemsigtighed samt den farve, der bruges til masken i billedvinduet. Et klik på farveknappen viser GIMPs farvevælger, hvor du kan ændre maskens farve.
Only available for selection masks. This allows you to assign a color tag to one or more selected channels. If you have a lot of channels this can make it easier to identify them by giving related channels the same color tag. To remove the color tag choose None.
The selection derived from the selected channels replaces the previously active selection.
The selection derived from the selected channels is added to the active selection. The final selection is merged from both.
The final selection is the subtraction of the selection derived from the selected channels from the active selection.
The final selection is the intersection of the selection derived from the selected channels with the active one. Only the selected parts common to both are kept.
Channels can be used to save and restore your selections. In the Channels dialog you can see a thumbnail representing the selection. Selection Masks are a graphical way to build selections into a gray level channel where white pixels are selected and black pixels are not selected. Therefore gray pixels are partially selected. You can think of them as feathering the selection, a smooth transition between selected and not selected. This is important to avoid the ugly pixelization effect when you fill the selection or when you erase its content after isolating a subject from background.
Der er flere måder at initialisere en markeringsmaske på.
From the main menu → if there is an active selection.
In the image window the bottom-left
button creates a
Quick Mask; the content
will be initialized with the active selection.
From the Channels dialog, when you click on the New channel button or from the context menu. When created, this Selection mask appears in the Channels dialog, named “Selection maskcopy” with a queuing number. You can change this by using the context menu that you get by right-clicking on the channel.
Når kanalen er initialiseret, valgt (fremhævet med blåt), synlig (øjeikon i dialogen) og vist, som du ønsker (farve- og uigennemsigtighedsegenskaber), kan du begynde at arbejde med alle maleværktøjerne. De anvendte farver er vigtige. Hvis du maler med en anden farve end hvid, grå eller sort, vil farveværdien (luminositet) blive brugt til at definere en grå (medium, lys eller mørk). Når din maske er malet, kan du omdanne den til en markering ved at klikke på knappen
(Kanal til markering) eller via genvejsmenuen.
Du kan arbejde i markeringsmasker ikke kun med maleværktøjet, men også med andre værktøjer. For eksempel kan du bruge markeringsværktøjerne til at udfylde områder ensartet med farveovergange eller mønstre. Ved at tilføje mange markeringsmasker i din liste kan du nemt sammensætte meget komplekse markeringer. Man kan sige, at en markeringsmaske er for en markering, som et lag er for et billede.
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Så længe en markeringsmaske er aktiveret, arbejder du i masken og ikke i billedet. For at arbejde i billedet skal du deaktivere alle markeringsmasker. Glem heller ikke at stoppe visningen af masker i billedet ved at fjerne øjeikonet. Tjek også, at alle RGB- og alfakanaler er aktiveret og vises i billedet. |
A Quick Mask is a Selection Mask intended to be used temporarily to paint a selection. Temporarily means that, unlike a normal selection mask, it will be deleted from the channel list after its transformation to selection. The selection tools sometimes show their limits when they have to be used for doing complex drawing selection, as progressive. In this case, using the Quick Mask is a good idea which can give very good results.
The Quick Mask can be activated in different ways:
From the main menu: → .
By clicking the bottom-left
button highlighted in the screenshot.
Ved at bruge genvejen Skift+Q.
To initialize a Quick Mask,
click the bottom-left
button in the image window. If a selection was
active in your image, then its content appears unchanged while the
border is covered with a translucent red color. If no selection was
active then all the image is covered with a translucent red color.
Another click on the bottom-left button will deactivate the quick mask.
From the Channels dialog you can double click on the name or the
thumbnail to edit the QMask attributes. Then you
can change the Opacity and its filling color. At
every moment you can hide the mask by clicking on the eye icon
in front of the QMask.
Masken er kodet i gråtoner, så du skal bruge hvid eller grå for at mindske det område, der afgrænses af masken, og sort for at øge det. Det område, der er malet i lys eller mørk grå, vil være overgangsområder for markeringen som udtynding. Når din maske er klar, klikker du igen på knappen nederst til venstre i billedvinduet, og ekspresmasken fjernes fra kanallisten og konverteres til en markering.
Formålet med Ekspresmaske er at male en markering og dens overgange med maleværktøjerne uden at skulle bekymre sig om at håndtere markeringsmasker. Det er en god måde at isolere et motiv i et billede på, for når først markeringen er lavet, behøver du kun at fjerne indholdet (eller omvendt, hvis motivet er i markeringen).
Screenshot of the image window with activated Quick Mask. As long as the Quick Mask is activated, all operations are done on it. A gradient from black (left) to white (right) has been applied to the mask.
The Quick Mask is now disabled. The selection occupies the right half part of the image (marching ants) because the limit of the selection is at the middle of the gradient.
Der tilføjes nu et penselstrøg, mens markeringen er aktiveret. Mærkeligt! Selvom farveovergangen ikke er synlig, forbliver den aktiv over hele billedet, både i markerede og umarkerede områder!
After the Quick Mask Button is pressed, the command generates a temporary 8-bit (0-255) channel, on which the progressive selection work is stored. If a selection is already present the mask is initialized with the content of the selection. Once Quick Mask has been activated, the image is covered by a red semi-transparent veil. This one represents the non-selected pixels. Any paint tool can be used to create the selection on the Quick Mask. They should use only grayscale color, conforming the channel properties, white enabling to define the future selected place. The selection will be displayed as soon as the Quick Mask will be toggled but its temporary channel will not be available anymore.
![[Vink]](images/tip.png)
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To save in a channel the selection done with the Quick Mask select in the main menu → . |
Åbn et billede eller opret et nyt dokument.
Activate the Quick Mask using the left-bottom button in the image window. If a selection is present the mask is initialized with the content of the selection.
Choose a drawing tool and use it with grayscale colors on the Quick Mask.
Deactivate the Quick Mask using the left-bottom button in the image window.
