Module gwy :: Class Gradient

Class Gradient

A map from numbers to RGBA colors

Gradient is a map from interval [0,1] to RGB(A) color space. Each gradient is defined by an ordered set of color points, the first of them is always at 0.0, the last at 1.0 (thus each gradient must consist of at least two points). Between them, the color is interpolated. Color points of modifiable gradients (see Resource) can be edited with functions like Gradient.insert_point(), Gradient.set_point_color(), or Gradient.set_points().

Gradient objects can be obtained from gwy_gradients_get_gradient(). New gradients can be created with Inventory.new_item() on the Inventory returned by gwy_gradients().

Instance Methods

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get_color(x, color)
Computes the color at a given position of a color gradient.

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sample_to_pixbuf(pixbuf)
Samples a color gradient to a provided pixbuf.

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get_npoints()
Returns the number of points in a color gradient.

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get_point(index_)
Returns the point at given index of a color gradient.

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set_point(index_, point)
Sets a single color point in a color gradient.

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set_point_color(index_, color)
Sets the color of a color gradient point without moving it.

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delete_point(index_)
Deletes a point at given index in a color gradient.

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reset()
Resets a gradient to the default two-point gray scale state.

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get_points()
Returns the complete set of color points of a gradient.

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set_points(npoints, points)
Sets the complete color gradient definition to a given set of points.

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set_from_samples(nsamples, samples, threshold)
Reconstructs a color gradient definition from sampled colors.

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Method Details

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get_color(x, color)

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Computes the color at a given position of a color gradient.

Parameters:

x - Position in gradient, in range 0..1. (float)
color - Color to fill with interpolated color at position x. (RGBA)

sample_to_pixbuf(pixbuf)

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Samples a color gradient to a provided pixbuf.

Unlike Gradient.sample() which simply takes samples at equidistant points this method uses supersampling and thus it gives a bit better looking gradient presentation.

Parameters:

pixbuf - A pixbuf to sample gradient to (in horizontal direction). (gdk.Pixbuf)

get_npoints()

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Returns the number of points in a color gradient.

Returns:: The number of points in gradient. (int)

get_point(index_)

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Returns the point at given index of a color gradient.

Parameters:

index_ - Color point index in gradient. (int)

Returns:

Color point at index_. (GradientPoint)

set_point(index_, point)

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Sets a single color point in a color gradient.

It is an error to try to move points beyond its neighbours, or to move first (or last) point from 0 (or 1).

Parameters:

index_ - Color point index in gradient. (int)
point - Color point to replace current point at index_ with. (const-GradientPoint*)

set_point_color(index_, color)

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Sets the color of a color gradient point without moving it.

Parameters:

index_ - Color point index in gradient. (int)
color - Color to set the point to. (const-RGBA*)

delete_point(index_)

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Deletes a point at given index in a color gradient.

It is not possible to delete points in gradients with less than 3 points. First and last points should not be deleted unless there's another point with x = 0 or x = 1 present.

Parameters:

index_ - Color point index in gradient. (int)

get_points()

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Returns the complete set of color points of a gradient.

Returns:: Tuple consisting of 2 values (value, npoints). ((const-GradientPoint*), (int))

set_points(npoints, points)

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Sets the complete color gradient definition to a given set of points.

The point positions should be ordered, and first point should start at 0.0, last end at 1.0. There should be no redundant points.

Parameters:

npoints - The length of points. (int)
points - Color points to set as new gradient definition. (const-GradientPoint*)

set_from_samples(nsamples, samples, threshold)

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Reconstructs a color gradient definition from sampled colors.

The result is usually approximate.

Parameters:

nsamples - Number of samples, it must be at least one. (int)
samples - Sampled color gradient in GdkPixbuf-like RRGGBBAA form. (string)
threshold - Maximum allowed difference (for color components in range 0..1). When negative, default value 1/80 suitable for most purposes is used. (float)