Capítulo 3. First Steps with GIMP
| Parte I. Primeros pasos |

## Capítulo 3. First Steps with GIMP

## 1. Conceptos básicos

Figura 3.1. Wilber, la mascota de GIMP

The Wilber Construction Kit ( src/images/Wilber_Construction_Kit_original.xcf) allows you to give GIMP's mascot named Wilber a different appearance. It is the work of Tuomas Kuosmanen (tigert).

Esta sección es una breve introducción a los conceptos básicos y a la terminología usada en GIMP. Los conceptos aquí presentados serán explicados en profundidad en otra parte. Salvando unas pocas excepciones, se ha tratado de no llenar esta sección de una gran cantidad de enlaces y referencias cruzadas: todo lo referido aquí es de tan alto nivel que le será posible ubicarlo fácilmente en el índice.

Imágenes

  Las imágenes son las entidades básicas usadas en GIMP. Hablando rápidamente, una “imagen” se corresponde con un solo archivo, como por ejemplo un archivo TIFF o JPEG. También puede pensar en una imagen como lo correspondiente a una única ventana (aunque en verdad es posible tener múltiples ventanas todas mostrando la misma imagen). No es posible tener una ventana única que muestre más de una imagen, o una imagen que no tenga ventana que la muestre.

  Una imagen de GIMP puede ser algo más complicado de lo que parece. En vez de pensar en ella como un dibujo en una hoja de papel, debería verla más como un pila de hojas, llamadas “capas”. Además de una pila de capas, una imagen de GIMP puede contener una máscara de selección, un conjunto de canales y un conjunto de rutas. De hecho, GIMP proporciona un mecanismo para agregar piezas arbitrarias de datos a una imagen, llamadas “parásitos”.

  En GIMP, es posible tener muchas imágenes abiertas al mismo tiempo. Aunque las imágenes grandes pueden usar muchos megabytes de memoria, GIMP usa un sofisticado sistema de gestión de memoria basado en bloques de píxeles que permite a GIMP manejar imágenes muy grandes sin esfuerzo. Sin embargo hay límites, y disponer de una mayor cantidad de memoria puede mejorar las prestaciones del sistema.

Capas

  If a simple image can be compared to a single sheet of paper, an image with layers is likened to a sheaf of transparent papers stacked one on top of the other. You can draw on each paper, but still see the content of the other sheets through the transparent areas. You can also move one sheet in relation to the others. Sophisticated GIMP users often deal with images containing many layers, even dozens of them. Layers need not be opaque, and they need not cover the entire extent of an image, so when you look at an image's display, you may see more than just the top layer: you may see elements of many layers. For more info see Introduction to Layers.

Resolución

  Digital images consist of a grid of square pixels. Each image has a size measured in two dimensions, such as 900 pixels wide by 600 pixels high. But pixels don't have a set size in physical space. To set up an image for printing, we use a value called resolution, defined as the ratio between an image's size in pixels and its physical size (usually in inches) when it is printed on paper. Most file formats (but not all) can save this value, which is expressed as ppi—pixels per inch.

  When printing a file, the resolution determines the size the image will have on paper, and as a result, the physical size of the pixels. The same 900×600 pixel image may be printed as a small 3×2" card with barely noticeable pixels—or as a large poster with large, chunky pixels.

  Images imported from cameras and mobile devices tend to have a resolution attached to the file. The resolution is usually 72 or 96 ppi. It is important to realize that this resolution is arbitrary and was chosen for historic reasons. You can always change the resolution with GIMP—this has no effect on the actual image pixels. Furthermore, for uses such as displaying images online, on mobile devices, television or video games—in short, any use that is not print—the resolution value is meaningless and is ignored. Instead, the image is usually displayed so that each image pixel conforms to one screen pixel.

Canales

  Un canal es un componente del color de un píxel. Para un píxel coloreado en GIMP, estos componentes son generalmente rojo, verde, azul y, a veces, transparencia (alfa). Para una imagen en escala de grises, son gris y alfa, y para una imagen de color indexada, son indexado y alfa.

  The entire rectangular array of any one of the color components for all of the pixels in an image is also referred to as a Channel. You can see these color channels with the Channels Dialog.

  Cuando se muestra la imagen, GIMP junta estos componentes para formar los colores del píxel para la pantalla, impresora u otro dispositivo de salida. Algunos de estos dispositivos pueden usar canales diferentes para rojo, verde y azul. Si ocurre esto, los canales de GIMP se convierten en los apropiados para el dispositivo cuando se muestra la imagen.

  Los canales pueden ser útiles cuando trabaja sobre una imagen que necesita ajustes en un color en particular. Por ejemplo, si quiere quitar los “ojos rojos” de una fotografía, podría operar sobre el canal rojo.

  Puede ver los canales como máscaras que permiten o restringen la salida del color que el canal representa. Mediante el uso de filtros en la información del canal, puede crear muchos efectos variados y sutiles sobre una imagen. Un ejemplo sencillo del uso de un filtro sobre los canales de color es el filtro Mezclador de canales.

  Además de estos canales, GIMP también le permite crear otros canales (o más correctamente, máscaras de canal), que se muestran en la parte inferior del diálogo de canales. Puede crear un canal nuevo o guardar una selección a un canal (máscara). Hay más información sobre las máscaras de canal en la entrada del glosario máscaras.

Selecciones

  Often when modifying an image, you only want a part of the image to be affected. The “selection” mechanism makes this possible. Each image has its own selection, which you normally see as a moving dashed line separating the selected parts from the unselected parts (the so-called “marching ants”). Actually this is a bit misleading: selection in GIMP is graded, not all-or-nothing, and really the selection is represented by a full-fledged grayscale channel. The dashed line that you normally see is simply a contour line at the 50%-selected level. At any time, though, you can visualize the selection channel in all its glorious detail by toggling the Quick Mask button.

  A large component of learning how to use GIMP effectively is acquiring the art of making good selections—selections that contain exactly what you need and nothing more. Because selection-handling is so centrally important, GIMP provides many tools for doing it: an assortment of selection-making tools, a menu of selection operations, and the ability to switch to Quick Mask mode, in which you can treat the selection channel as though it were a color channel, thereby “painting the selection”. For more information, see also The Selection.

Deshacer

  When you make mistakes, you can undo them. Nearly everything you can do to an image is undoable. In fact, you can usually undo a substantial number of the most recent things you did, if you decide that they were misguided. GIMP makes this possible by keeping a history of your actions. This history consumes memory, though, so undoability is not infinite. Some actions use very little undo memory, so that you can do dozens of them before the earliest ones are deleted from this history; other types of actions require massive amounts of undo memory.

  You can configure the amount of memory GIMP allows for the undo history of each image, but in any situation, you should always be able to undo at least your 2-3 most recent actions. The most important action that is not undoable is closing an image. For this reason, GIMP asks you to confirm that you really want to close the image if you have made any changes to it. For more information, see also Undoing.

Complementos

  A lot of the things that you do to an image in GIMP are done by GIMP itself. However, GIMP also makes extensive use of “plug-ins”, which are external programs that interact very closely with GIMP, and are capable of manipulating images and other GIMP objects in very sophisticated ways. Many important plug-ins are bundled with GIMP, but there are also many available by other means. In fact, writing plug-ins (and scripts) is the easiest way for people not on the GIMP development team to add new capabilities to GIMP.

  Todos los comandos en el menú Filtros, y una cantidad sustancial de comandos en otros menús, están en realidad implementados como complementos.

Guiones (scripts)

  In addition to plug-ins, GIMP can also make use of scripts. Scripts are written in a language called Script-Fu, which is unique to GIMP (for those who care, it is a dialect of the Lisp-like language called Scheme). In the past there was a clear distinction between scripts and plug-ins, but that is disappearing. Depending on which Script-Fu interpreter you use, Scheme scripts can also be installed as plug-ins.

Capítulo 2. Starting GIMP |  | 2. Ventanas principales

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