Gradient

This transformation generates an image the same size as the current image filled with a graduated sequence of colors. This gradient image is optionally applied to the input image as a normal or subtractive filter -- a useful option when you want to lighten or darken the input image.

To create a gradient without an input image, first use the File New command to create a blank input image of the desired size and resolution.

There are several transformations that fall within the Gradient category:

Linear Gradient -- varies along a straight line from a starting point to an ending point – linear gradients may be horizontal, vertical or at an angle.

Oval Gradient -- varies outward in concentric ellipses, circles or rectangles from the center to an ending radius

Sweep Gradient -- varies by angle around a center point. Linear, Oval and Sweep gradients work based on either a color line or a curve control that specifies the sequence of colors or gray levels that the gradient will apply.

Multipoint Gradient -- specified at a number of points. Multipoint gradient works by letting you specify colors or gray levels at a series of points in the input image. It then interpolates smoothly between those points to fill out the gradient everywhere in the image.

Positioning the Gradient

You position the gradient by adjusting points that appear as an overlay on the input image. If you need to drag control points outside the input image, first zoom it out to make it smaller.

For a linear gradient, you position the starting and ending point of the gradient line. Picture Window displays additional lines at right angles to the gradient line for reference purposes. The gradient colors are painted in sequence perpendicular to the line connecting the starting and ending point. The starting color is painted beyond the starting point and the ending color is painted beyond the ending point. You can adjust the positions of intermediate points on the gradient either by dragging control points in the overlay or by moving them on the color line or curve controls. Note that you cannot drag one control point past another as they must remain in order.

For an oval gradient, you position a box that contains the outermost ellipse or rectangle of the sequence. The gradient colors are painted in ellipses (or rectangles) that grow outward from the center. The starting color is painted at the center and the ending color at the outermost ellipse (or rectangle) and beyond. When creating an oval or rectangular gradient, you can force it to be circular or square by holding down the shift key while you drag one of the four edge control points. You can adjust the positions of intermediate points on the gradient either by dragging control points in the overlay or by moving them on the color line or curve controls. Note that you cannot drag one control point past another as they must remain in order. To rotate the oval, drag the line that connects the center to the outermost oval.

For a sweep gradient, you position the center of rotation and the rotation angle. The gradient colors are painted along radial line extending from the center. The starting color is painted at the starting angle and proceeds around for a full 360 degrees. The overlay contains a line for each control point on the color line or point on the curve. The line at the starting angle is displayed in a slightly different color so you can identify it. You can drag anywhere on this line to rotate the gradient or you can drag the center point to shift the center of rotation. You can adjust the positions of intermediate points on the gradient either by dragging the associated rays in the overlay or by moving them on the color line or curve controls. Note that you cannot drag one control point past another as they must remain in order.

For multi-point gradients, you can position an existing point by clicking and dragging it, add a new point by Shift-clicking on the input image (holding down either Shift key while clicking with the left mouse button) at the desired location, or remove an existing point by Ctrl-clicking on it (holding down the Ctrl key while clicking with the left mouse button) in the input image window.

Except for multi-point gradients, you may position control points outside the boundaries of the input image, and this is necessary to obtain certain effects where the gradient runs off the edge of the image. To do this usually requires zooming input image out to make it small enough that you have room to place the control points.

Amount

The amount control lets you control how much of the gradient transformation is applied to the input image. You can apply a percentage of the transformation to the entire image, or you can specify an amount mask to restrict the effects of the transformation to only part of the input image.

Gradient Type

Depending on the transformation you select, you can create different effects:

Linear

Linear gradients vary according to the color line in bands. You control the location and orientation of the linear gradient by adjusting control points displayed over the input image. You adjust the gradient colors and transitions using the color line control (see below). If you select Horizontal or Vertical, the control points are fixed to make a horizontal or vertical gradient. Linear gradients can be at any angle.

Oval

Oval and rectangular gradients vary according to the color line in a series of ellipses or rectangles that grow outward from a central point. You control the location and size of the gradient by adjusting control points displayed over the input image. You adjust the gradient colors and transitions using the color line control (see below).

Sweep

Sweep gradients vary according to angle from a central point. You control the location of the gradient by adjusting control points displayed over the input image. You adjust the gradient colors and transitions using the color line control (see below).

Multipoint

When you choose multi-point, the color line, cycle, and antialias controls (see below) are replaced by a single color control that lets you specify the color of the current point. Multi-point gradients are created by specifying colors at a set of locations in the image – the area between the specified points is then filled in using two-dimensional interpolation to blend the specified colors. The more points you use, the more control you exert over the gradient. Shift-click on the input image to create a new point; ctrl-click on an existing point to remove it. To reposition a point, click and drag it.

A Match Input Image checkbox is also displayed; when this checkbox is selected, the color associated with a given point is automatically made to match that of the corresponding location in the input image whenever you reposition the point. This is helpful when using a multi-point gradient to replicate the gradient in an input image.

The Method control lets you select different interpolation methods. Some of the methods also have an adjustable Scale slider you can use to vary the effect.

Operation

This control lets you select how the gradient should be combined with the input image. The options are:

Fill -- This operation causes the gradient to replace the input image (to the extent specified by the Amount control).

Filter -- This operation applies the gradient to the input image as a filter, similar to placing a transparent color or neutral density filter over the image. If the gradient consists of only black and white colors, the input image is darkened depending on the darkness of the gradient—where the gradient is white the input image remains unchanged.

Subtractive Filter -- This operation applies the gradient to the input image as a subtractive filter, similar making a negative of filtering a negative of the input image with a negative of the gradient. If the gradient consists of only black and white colors, the input image is lightened depending on the lightness of the gradient -- where the gradient is black the input image remains unchanged.

Cycle

This control lets you generate multiple cycles of the gradient color in equally spaced bands or rings.

Antialias

Without antialiasing, if the color sequence you specify with the color line control has abrupt transitions, then the corresponding color boundaries may appear jagged in the output image. Increasing the antialias setting will eliminate these rough edges, but will take more computation time. If the gradient color transitions are all smooth, antialiasing is unnecessary.

Color Line

The color line control lets you specify the gradient color sequence. The color at the left end of the color line is the starting color of the gradient; the color at the right end is the ending color.

Start/End Color and Curve

If you select Curve from the Settings menu (see below), the color line is replaced by a curve. By adjusting the curve you can specify any kind of transition you want between the Start Color and the End Color.

Settings Menu

The following two options affect how you specify gradients when the gradient type is horizontal, vertical, linear, oval, rectangular, or radial sweep.

Line -- the gradient is derived from a color line.

Curve -- the gradient is derived from a curve that specifies a transition from a starting color to an ending color.

The following options determine whether you create a color or a black and white gradient.

Color -- Lets select colors for the color line or starting and ending curve colors.

Black & White -- You can only select gray levels for the color line and starting and ending curve colors. This forces the resulting gradient image to be a black and white image you can use for example as a mask.