3.4. Váš první Script-Fu skript

Do you not need to stop and catch your breath? No? Well then, let's proceed with your fourth lesson — your first Script-Fu Script.

3.4.1. Vytvoření skriptu Text Box

One of the most common operations I perform in GIMP is creating a box with some text in it for a web page, a logo or whatever. However, you never quite know how big to make the initial image when you start out. You don't know how much space the text will fill with the font and font size you want.

Mistr Script-Fu (ale i nadaný student) si brzy uvědomí, že lze takový problém snadno a automaticky řešit pomocí Script-Fu.

Proto vytvoříme skript, který pojmenujeme Text Box a který vytvoří obrázek o velikosti přesně odpovídající zadanému textu. Uživatel bude mít možnost zvolit i řez písma, jeho velikost a barvu.

3.4.2. Editace a ukládání skriptů

Do této chvíle jsme pracovali se Script-Fu konzolí. Od této chvíle však budeme pracovat s textovými soubory.

Where you place your scripts is a matter of preference — if you have access to GIMP's default script directory, you can place your scripts there. However, I prefer keeping my personal scripts in my own script directory, to keep them separate from the factory-installed scripts.

In the ~/.config/GIMP/2.10/ directory that GIMP made off of your home directory, you should find a directory called scripts. GIMP will automatically look in your ~/.config/GIMP/2.10/ directory for a scripts directory, and add the scripts in this directory to the Script-Fu database. You should place your personal scripts here.

3.4.3. Úplné základy

Každý Script-Fu skript definuje alespoň jednu funkci, hlavní funkci skriptu. Ta je zodpovědná za činnost skriptu.

Every script must also register with the procedural database, so you can access it within GIMP.

Nejprve definujeme hlavní funkci:

        (define (script-fu-text-box inText inFont inFontSize inTextColor))
      

Here, we've defined a new function called script-fu-text-box that takes four parameters, which will later correspond to some text, a font, the font size, and the text's color. The function is currently empty and thus does nothing. So far, so good — nothing new, nothing fancy.

3.4.4. Jmenné konvence

Konvence jazyka Scheme pro vytváření jmen upřednostňují malá písmena a pomlčky, tak jako jsme učinili při výběru jména funkce. Při pojmenovávání jejích parametrů jsme se však od konvence odchýlili. Mám rád jména popisná, která o funkci nebo parametru hodně říkají, proto jsme pro parametry použili předponu in, která naznačuje, že parametry obsahují hodnoty předávané skriptu, nikoliv skriptem vytvořené. Pro proměnné vytvořené uvnitř skriptu používám předponu the.

It's GIMP convention to name your script functions script-fu-abc, because then when they're listed in the procedural database, they'll all show up under Script-Fu when you're listing the functions. This also helps distinguish them from plug-ins.

3.4.5. Registrace funkce

Now, let's register the function with GIMP. This is done by calling the function script-fu-register. When GIMP reads in a script, it will execute this function, which registers the script with the procedural database. You can place this function call wherever you wish in your script, but I usually place it at the end, after all my other code.

Zde je výpis naší registrační funkce (její parametry vzápětí vysvětlím):

  (script-fu-register
    "script-fu-text-box"                        ;func name
    "Text Box"                                  ;menu label
    "Creates a simple text box, sized to fit\
      around the user's choice of text,\
      font, font size, and color."              ;description
    "Michael Terry"                             ;author
    "copyright 1997, Michael Terry;\
      2009, the GIMP Documentation Team"        ;copyright notice
    "October 27, 1997"                          ;date created
    ""                     ;image type that the script works on
    SF-STRING      "Text"          "Text Box"   ;a string variable
    SF-FONT        "Font"          "Charter"    ;a font variable
    SF-ADJUSTMENT  "Font size"     '(50 1 1000 1 10 0 1)
                                                ;a spin-button
    SF-COLOR       "Color"         '(0 0 0)     ;color variable
  )
  (script-fu-menu-register "script-fu-text-box" "<Image>/File/Create/Text")
      

If you save these functions in a text file with a .scm suffix in your script directory, then choose FiltersScript-FuRefresh Scripts, this new script will appear as FileCreateTextText Box.

Pokud ale skript spustíte, neudělá samozřejmě nic užitečného, ale uvidíte výzvy vytvořené při registraci skriptu (podrobnosti dále).

Finally, if you invoke the Procedure Browser ( HelpProcedure Browser), you'll notice that our script now appears in the database.

3.4.6. Jednotlivé kroky registrace skriptu

To register our script with GIMP, we call the function script-fu-register, fill in the seven required parameters and add our script's own parameters, along with a description and default value for each parameter.

Povinné parametry

  • The name of the function we defined. This is the function called when our script is invoked (the entry-point into our script). This is necessary because we may define additional functions within the same file, and GIMP needs to know which of these functions to call. In our example, we only defined one function, text-box, which we registered.

  • The location in the menu where the script will be inserted. The exact location of the script is specified like a path in Unix, with the root of the path being image menu as <Image>.[6]

    If your script does not operate on an existing image (and thus creates a new image, like our Text Box script will), you'll want to insert it in the image window menu, which you can access through the image menu bar, by right-clicking the image window, by clicking the menu button icon at the left-top corner of the image window, or by pressing F10.

    If your script is intended to work on an image being edited, you'll want to insert it in the image window menu. The rest of the path points to the menu lists, menus and sub-menus. Thus, we registered our Text Box script in the Text menu of the Create menu of the File menu.[7] (FileCreateTextText Box).

    If you notice, the Text sub-menu in the File/Create menu wasn't there when we began — GIMP automatically creates any menus not already existing.

  • Popis skriptu, který se zobrazuje v Prohlížeči procedur.

  • Vaše jméno (jméno autora skriptu).

  • Copyright, informace o autorských právech.

  • Datum, kdy byl skript napsán nebo naposledy revidován.

  • The types of images the script works on. This may be any of the following: RGB, RGBA, GRAY, GRAYA, INDEXED, INDEXEDA. Or it may be none at all — in our case, we're creating an image, and thus don't need to define the type of image on which we work.

Obrázek 13.3. The menu of our script.

The menu of our script.

3.4.7. Registrace parametrů skriptu

Po uvedení obecných, povinných parametrů je třeba uvést parametry, které vyžaduje náš skript. V seznamu těchto parametrů je také třeba uvést jejich typ, což umožní správně zobrazit dialog, ve kterém uživatel parametry nastavuje. Také zadáme výchozí hodnoty těchto parametrů.

Tato část registračního procesu používá následující formát:

Typ parametru

Popis

Příklad

SF-IMAGE

If your script operates on an open image, this should be the first parameter after the required parameters. GIMP will pass in a reference to the image in this parameter.

3

SF-DRAWABLE

If your script operates on an open image, this should be the second parameter after the SF-IMAGE param. It refers to the active layer. GIMP will pass in a reference to the active layer in this parameter.

17

SF-VALUE

Accepts numbers and strings. Note that quotes must be escaped for default text, so better use SF-STRING.

42

SF-STRING

Přijímá řetězce.

"Nějaký text"

SF-COLOR

Označuje parametr vyžadující barvu.

'(0 102 255)

SF-TOGGLE

Přijímá booleovskou hodnotu (pravda či nepravda). V dialogu se zobrazuje jako zaškrtávací políčko, přepínač.

TRUE nebo FALSE

3.4.8. The Script-Fu parameter API[8]

[Poznámka] Poznámka

Beside the above parameter types there are more types for the interactive mode, each of them will create a widget in the control dialog. You will find a list of these parameters with descriptions and examples in the test script plug-ins/script-fu/scripts/test-sphere.scm shipped with the GIMP source code.

Typ parametru

Popis

SF-ADJUSTMENT

Creates an adjustment widget in the dialog.

SF-ADJUSTMENT "label" '(value lower upper step_inc page_inc digits type)

Widget arguments list
ElementPopis
"label"Text printed before the widget.
jasValue print at the start.
lower / upperThe lower / upper values (range of choice).
step_incIncrement/decrement value.
page_incIncrement/decrement value using page key.
digitsDigits after the point (decimal part).
typeOne of: SF-SLIDER or 0, SF-SPINNER or 1

SF-COLOR

TODO: Description

SF-COLOR "label" '(red green blue)

or

SF-COLOR "label" "color"

Widget arguments list
ElementPopis
"label"Text printed before the widget.
'(red green blue) List of three values for the red, green and blue components.
"color"Color name in CSS notation.

SF-FONT

TODO: Description

(gimp-text-fontname image drawable x-pos y-pos text border antialias size unit font)

(gimp-text-get-extents-fontname text size unit font)

where font is the fontname you get. The size specified in the fontname is silently ignored. It is only used in the font-selector. So you are asked to set it to a useful value (24 pixels is a good choice).

SF-FONT "label" "fontname"

Widget arguments list
ElementPopis
"label"Text printed before the widget.
"fontname"Name of the default font.

SF-BRUSH

TODO: Description

SF-BRUSH "Brush" '("Circle (03)" 100 44 0)

Here the brush dialog will be popped up with a default brush of Circle (03) opacity 100 spacing 44 and paint mode of Normal (value 0).

If this selection was unchanged the value passed to the function as a parameter would be '("Circle (03)" 100 44 0).

SF-PATTERN

TODO: Description

SF-PATTERN "Pattern" "Maple Leaves"

The value returned when the script is invoked is a string containing the pattern name. If the above selection was not altered the string would contain "Maple Leaves".

SF-GRADIENT

TODO: Description

If the button is pressed a gradient selection dialog will popup.

SF-GRADIENT "Gradient" "Deep Sea"

The value returned when the script is invoked is a string containing the gradient name. If the above selection was not altered the string would contain "Deep Sea".

SF-PALETTE

TODO: Description

If the button is pressed a palette selection dialog will popup.

SF-PALETTE "Palette" "Named Colors"

The value returned when the script is invoked is a string containing the palette name. If the above selection was not altered the string would contain "Named Colors".

SF-FILENAME

TODO: Description

If the button is pressed a file selection dialog will popup.

SF-FILENAME "label" (string-append "" gimp-data-directory "/scripts/beavis.jpg")

The value returned when the script is invoked is a string containing the filename.

SF-DIRNAME

TODO: Description

SF-DIRNAME "label" "/var/tmp/images"

The value returned when the script is invoked is a string containing the dirname.

SF-OPTION

TODO: Description

The first option is the default choice.

SF-OPTION "label" '("option1" "option2")

The value returned when the script is invoked is the number of the chosen option, where the option first is counted as 0.

SF-ENUM

It will create a widget in the control dialog. The widget is a combo-box showing all enum values for the given enum type. This has to be the name of a registered enum, without the "Gimp" prefix. The second parameter specifies the default value, using the enum value's nick.

SF-ENUM "Interpolation" '("InterpolationType" "linear")

The value returned when the script is invoked corresponds to chosen enum value.



[6] Before version 2.6, <Toolbox> could be also used, but now the toolbox menu is removed, so don't use it.

[7] The original, written by Mike, says put the menu entry in the Script-Fu menu of the Xtns menu at the Toolbox, but since version 2.6, the Toolbox menu had been removed and merged with the image window menubar.

[8] This section is not part of the original tutorial.