第6章 GIMP から画像を引き出す

目次

1. ファイル
1.1. 画像の保存方法とエクスポート方法
1.2. ファイル形式
2. ウェブ用の画像の作成
2.1. 画像の容量最適化と品質
2.2. さらにファイル容量を削減
2.3. 透過画像の保存

1. ファイル

GIMP is capable of reading and writing a large variety of graphics file formats. With the exception of GIMP's native XCF file format, file handling is done by plug-ins. This makes it relatively easy to extend GIMP to support new file types when the need arises.

1.1. 画像の保存方法とエクスポート方法

[注記] 注記

When you open an image, let's say in JPG or PNG file format, it is imported into GIMP's own XCF format, as a new project.

For example, a sunflower.png image will be loaded as *[sunflower] (imported)-1.0 (indexed color, 1 layer). The leading asterisk indicates that this file has been changed. This image can be saved as sunflower.xcf by using the Save command. If you need your image in another format, you should use the Export command.

When you are finished working with an image, you will save the results. In fact, it is often a good idea to save at intermediate stages too. GIMP is a pretty robust program, but on rare occasions crashes have happened.

GIMP's native format XCF is special. It is the only format that can store everything about an image (with the exception of undo information). This is the reason that saving can only be done in this format. It makes the XCF format especially suited for storing intermediate results, and for saving images to be re-opened later in GIMP.

XCF files are not readable by most other programs that display images. Once you have finished editing your image, you can export it to the format of your choice. GIMP supports a wide range of formats. Most file formats that can be imported, can also be used for exporting.

1.2. ファイル形式

There are several commands for saving and exporting images. They are listed in the section covering the File Menu. More information on how to use them can be found there.

出来上がった画像を 保存する ファイル形式について、 GIMP は幾種類もの対応ができます。 ただしレイヤーや透明度をはじめ画像の情報を すべて 保存できる形式は、 GIMP 由来の XCF 形式をおいて他にないということは重要です。 これ以外の形式はいずれも、 画像の属性を一定の範囲は保存できても一部は失います。 どんな形式を選びその形式がどんな性能かを理解するのはあなた次第です。

画像のエクスポートで元の画像そのものが変更されるものではありませんので、 それが原因で何かを失なうおそれはありません。 画像のエクスポート を参照してください。

[注記] 注記

When you close an image (possibly by quitting GIMP), you are warned if the image has been changed without subsequently being saved (an asterisk is in front of the image name in the title bar of the main window).