이미지는 김프 사용의 가장 기본이 되는 부분입니다. 보통 “이미지”라고 하면 TIFF 나 JPEG 과 같은 하나의 파일을 가리킵니다. 또는 하나의 이미지가 열려 있는 창을 가리키는 말로 쓰는 경우도 있습니다. 하지만 엄밀히 말해 이는 올바르지 않습니다. 왜냐하면 여러 창에 같은 이미지를 열 수도 있기 때문입니다. 반대로 한 창에 여러 이미지를 띄우거나 창없이 이미지를 열수는 없습니다.

김프에서 이미지는 굉장히 복잡하게 구성되어 있습니다. 이는 기존의 그림이 그려진 종이라는 개념이 아니라 “레이어”라는 수많은 페이지로 이루어진 책과 같은 개념입니다. 김프 이미지에는 레이어 외에 선택 마스크, 채널, 경로 등도 포함됩니다. 또한 김프는 “parasites(기생충)”라고 부르는 이미지의 데이터 조각을 무작위로 이어붙이는 기술도 제공합니다.

김프에서는 동시에 많은 이미지들을 열 수 있습니다. 큰 이미지들을 동시에 열려면 많은 메모리가 필요하지만, 김프의 지능적인 타일기반 메모리 관리 시스템은 이러한 메모리 문제를 깔끔하게 처리할 수 있습니다. 하지만 한계는 있으므로 일반적으로는 사용 가능한 메모리를 늘이는 것이 좋습니다.

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.

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 96ppi. 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.

채널은 픽셀 색상을 구성하고 있는 요소 중 하나입니다. 김프에서 픽셀이 가진 색상은 일반적으로 빨강, 녹색, 파랑, 그리고 투명(알파)입니다. 그레이스케일 이미지의 경우에는 회색과 알파만 있고, 인덱스 이미지는 인덱스와 알파만 있습니다.

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.

김프에서는 이러한 요소들을 한데 모아 픽셀 색상을 구성하여 화면, 프린터, 기타 장치 등에 이미지를 표시합니다. 일부 출력 장치는 빨강, 녹색, 파랑 등의 다른 채널을 사용하기도 합니다. 이런 경우에는 김프에서 사용하는 각 채널이 해당 장치에 알맞는 채널로 자동 변환됩니다.

이미지의 특정 색상을 조절할 때 채널을 이용하면 편리합니다. 예를 들어 인물 사진에서 “적목 현상”을 제거하려면 빨강 채널에서 색상을 조절하면 됩니다.

You can look at channels as masks which allow or restrict the output of the color that the channel represents. By using Filters on the channel information, you can create many varied and subtle effects on an image. A simple example of using a Filter on the color channels is the Channel Mixer filter.

이러한 채널 외에 다른 채널(정확히는 채널 마스크)을 생성할 수 있습니다. 새로 생성한 채널은 채널 대화 상자의 아래부분에 표시됩니다. 직접 새 채널을 생성하거나 선택을 채널로(마스크) 기능을 이용해 저장할 수도 있습니다. 채널 마스크에 대한 더 자세한 사항은 용어집의 마스크 부분을 참고하십시오.

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.

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.

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.

그런 까닭에 필터 메뉴의 모든 명령과 다른 메뉴들의 많은 명령들은 플러그인으로 구현되어 있습니다.

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.