## 6. Gradients

图 7.22. Some examples of GIMP gradients.

Gradients from top to bottom: FG to BG (RGB); Full Saturation Spectrum CCW; Nauseating Headache; Browns; Four Bars

A gradient is a set of colors arranged in a linear order. The most basic use of gradients is by the Gradient tool, sometimes known as “gradient fill tool”: it works by filling the selection with colors from a gradient. You have many options to choose from for controlling the way the gradient colors are arranged within the selection. There are also other important ways to use gradients, including:

用渐变绘画

  GIMP的每个基本绘画工具都允许您选择使用渐变颜色。这使您能够创建从一端到另一端改变颜色的笔触。

渐变映射滤镜

  This filter is in the Colors menu, and allows you to “colorize” an image, using the color intensity of each point with the corresponding color from the active gradient (the intensity 0, very dark, is replaced by the color at most left end of the gradient, progressively until the intensity is 255, very light, replaced by the most right color of the gradient. See 第 8.39 节 “Gradient Map” for more information.

GIMP comes presupplied with a large number of gradients. You can also add new gradients that you create or download from other sources. You can access the full set of available gradients using the Gradients dialog, a dockable dialog that you can either activate when you need it, or keep around as a tab in a dock. The “current gradient”, used in most gradient-related operations, is shown in the Brush/Pattern/Gradient area of the Toolbox. Clicking on the gradient symbol in the Toolbox is an alternative way of bringing up the Gradients dialog.

Some quick examples of working with gradients (for more information see Gradient Tool) are:

- 将渐变放置在选区中：

  1. 选择一个渐变。

  2. 在选区的两个点之间使用鼠标单击并拖动混合工具。

  3. 颜色将垂直于鼠标拖动的方向并根据拖动的长度分布。

  图 7.23. 如何在选区中快速使用渐变

- 用渐变绘画：

  You can also use a gradient with one of the drawing tools (e.g. Pencil, Paintbrush or Airbrush) if you switch on Enable dynamics and set Dynamics to Color From Gradient. In the next step, set the gradients length and the Repeat style in the Fade Options section, and select a suitable gradient in the Color Options section. 第 3.2.6 节 “Dynamics Options” describes these parameters in more detail.

  The following example shows the impact on the Pencil tool.

  图 7.24. How to use a gradient with a drawing tool

  Tool settings

  Resulting succession of the gradients colors

- 具有相同渐变的不同产物：

  图 7.25. 渐变用法

  使用Tropical Colors渐变的四种方法：线性渐变填充，成形渐变填充，使用渐变颜色绘制的笔触，以及使用模糊笔刷绘制、然后使用渐变映射滤镜着色的笔触。

关于GIMP渐变的一些有用信息：

- The first gradients in the list are special: They use the colors from the Foreground/Background Colors Area in the Toolbox, instead of being fixed.

  - FG to BG (HSV Counter-Clockwise) represents the hue succession in a color wheel from the selected hue to 360°.

  - FG to BG (HSV Clockwise) represents the hue succession in a color wheel from the selected hue to 0°.

  - FG to BG (RGB) is the RGB representation of the gradient from the Foreground color to the Background color in Toolbox.

  - TheFG to BG (Hard Edge) gradient generates a gradient from the foreground color to the background color, with hard-edged transitions in between.

  - With FG to Transparent, the selected hue becomes more and more transparent. You can modify these colors by using the Color Selector. Thus, by altering the foreground and background colors, you can make these gradients transition smoothly between any two colors you want.

  - The FG to Transparent (Hard Edge) gradient generates a gradient from the foreground color to transparency, with hard-edged transitions in between.

    Using this gradient, you can generate patterns very quickly with the “Repeat” option, alternating repetitive colored shapes with full transparency over a given background. Does works best with shapes like spiral, radial, square and linear.

- 渐变不仅涉及颜色变化，还涉及不透明度的变化。有些渐变是完全不透明的；其他包括透明或半透明部分。当您使用非不透明渐变填充或绘制时，图层的现有内容将在其后面显示出来。

- 您可以使用渐变编辑器创建新的自定义渐变。您不能修改随GIMP提供的渐变，但您可以复制它们或创建新的渐变，然后编辑它们。

The gradients that are supplied with GIMP are stored in a system `gradients` folder.

Gradients that you create are automatically saved in the `gradients` folder of your personal GIMP directory. Any gradient files (ending with the extension `.ggr`) found in one of these folders, will automatically be loaded when you start GIMP. You can add more directories to the gradient search path, if you want to, in the Gradients tab of the Data Folders section of the Preferences dialog.

GIMP can also load gradient files in SVG format, used by many vector graphics programs. To make GIMP load an SVG gradient file, place it in the `gradients` folder of your personal GIMP directory, or any other folder in your gradient search path.

| 提示
You can find a large number of interesting SVG gradients on the web, in particular at OpenClipArt Gradients [OPENCLIPART-GRADIENT].

5.4. Creating a brush quickly |  | 7. Patterns

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