3.4. Blend
| 3. Paint Tools |

### 3.4. Blend

图 13.55. The Blend tool in Toolbox

This tool fills the selected area with a gradient blend of the foreground and background colors by default, but there are many options. To make a blend, drag the cursor in the direction you want the gradient to go, and release the mouse button when you feel you have the right position and size of your blend. The softness of the blend depends on how far you drag the cursor. The shorter the drag distance, the sharper it will be.

There are an astonishing number of things you can do with this tool, and the possibilities may seem a bit overwhelming at first. The two most important options you have are the Gradient and the Shape. Clicking the Gradient button in the tool options brings up a Gradient Select window, allowing you to choose from among a variety of gradients supplied with GIMP; you can also construct and save custom gradients. Further information about gradients can be found in 第 10 节 “Gradients” and 第 3.4 节 “Gradients Dialog”.

For Shape, there are 11 options: Linear, Bilinear, Radial, Square, Conical (symmetric), Conical (asymmetric), Shaped (angular), Shaped (spherical), Shaped (dimpled), Spiral (clockwise), and Spiral (counterclockwise); these are described in detail below. The Shaped options are the most interesting: they cause the gradient to follow the shape of the selection boundary, no matter how twisty it is. Unlike the other shapes, Shaped gradients are not affected by the length or direction of the line you draw: for them as well as every other type of gradient you are required to click inside the selection and move the mouse, but a Shaped appears the same no matter where you click or how you move.

| 提示
Check out the Difference option in the Mode menu, where doing the same thing (even with full opacity) will result in fantastic swirling patterns, changing and adding every time you drag the cursor.

#### 3.4.1. Activating the Tool

There are different possibilities to activate the tool:

- From the image-menu: Tools → Paint Tools → Blend.

- By clicking the tool icon .

- By clicking on the L keyboard shortcut.

#### 3.4.2. Key modifiers (Defaults)

Ctrl

  Ctrl is used to create straight lines that are constrained to 15 degree absolute angles.

#### 3.4.3. Options

图 13.56. “Blend” tool options

Normally, tool options are displayed in a window attached under the Toolbox as soon as you activate a tool. If they are not, you can access them from the image menu bar through Windows → Dockable Windows → Tool Options which opens the option window of the selected tool.

Mode; Opacity
  See the Common Paint Tool Options for a description of tool options that apply to many or all paint tools.
Gradient

  A variety of gradient patterns can be selected from the drop-down list. The tool causes a shading pattern that transitions from foreground to background color or introducing others colors, in the direction the user determines by drawing a line in the image. For the purposes of drawing the gradient, the Reverse check-box reverse the gradient direction with the effect, for instance, of swapping the foreground and background colors.

Offset

  The Offset value permits to increase the “slope” of the gradient. It determines how far from the clicked starting point the gradient will begin. Shaped forms are not affected by this option.

  图 13.57. “Blend” tool: Offset example

  Top, Offset = 0 ; Bottom, Offset = 50%

Shape

  The GIMP provides 11 shapes, which can be selected from the drop-down list. Details on each of the shapes are given below.

  图 13.58. Examples of gradient shapes

  Linear

  Bi-Linear

  Radial

  Linear

    This gradient begins with the foreground color at the starting point of the drawn line and transitions linearly to the background color at the ending point.

  Bi-Linear

    This shape proceeds in both directions from the starting point, for a distance determined by the length of the drawn line. It is useful, for example, for giving the appearance of a cylinder.

  Radial

    This gradient gives a circle, with foreground color at the center and background color outside the circle. It gives the appearance of a sphere without directional lighting.

  Square; Shaped

    图 13.59. Square-shaped gradient examples

    Square

    Shaped (angular)

    Shaped (spherical)

    Shaped (dimpled)

    There are four shapes that are some variant on a square: Square, Shaped (angular), Shaped (spherical), and Shaped (dimpled). They all put the foreground color at the center of a square, whose center is at the start of the drawn line, and whose half-diagonal is the length of the drawn line. The four options provide a variety in the manner in which the gradient is calculated; experimentation is the best means of seeing the differences.

  Conical (symmetric); Conical (asymmetric)

    图 13.60. Conical gradient examples

    Conical (symmetrical)

    Conical (asymmetrical)

    The Conical (symmetrical) shape gives the sensation of looking down at the tip of a cone, which appears to be illuminated with the background color from a direction determined by the direction of the drawn line.

    Conical (asymmetric) is similar to Conical (symmetric) except that the "cone" appears to have a ridge where the line is drawn.

  Spiral (clockwise); Spiral (counterclockwise)

    图 13.61. Spiral gradient examples

    Spiral (clockwise)

    Spiral (counterclockwise)

    The Spiral shape provide spirals whose repeat width is determined by the length of the drawn line.

Repeat

  There are two repeat modes: Sawtooth Wave and Triangular Wave. The Sawtooth pattern is achieved by beginning with the foreground, transitioning to the background, then starting over with the foreground. The Triangular starts with the foreground, transitions to the background, then transitions back to the foreground.

Dithering

  Dithering is fully explained in the Glossary

Adaptive Supersampling

  This a more sophisticated means of smoothing the "jagged" effect of a sharp transition of color along a slanted or curved line. Only tests can allow you to choose.

3.3. Bucket Fill |  | 3.5. Pencil