avg

Animated Scalable Vector Graphics (SVG)

This library provides an easy way to make animations using the scalable vector graphics (SVG) format. SVG is a web-standard format and can be opened by all modern web browsers. An SVG can often be placed wherever any other image type can be placed. Even many email clients can view SVG animations. This format provides an easy way for others to view an animation without requiring any additional software installation.

Shapes

First, create your shapes with the shape class. A shape object can be initialized with the following parameters:

• x : float or array, default 0.0 x values of the shape or the x-axis radius of an ellipse.
• y : float or array, default 0.0 y values of the shape or the y-axis radius of an ellipse.
• stroke : float or array, default 1.0 Stroke width or animated widths.
• color : float or array, default 0x000000 Stroke or fill color or animated colors. It is a fill color or colors if stroke is a scalar zero.
• alpha : float or array, default 1.0 Opacity or animated opacity values. A 0.0 means fully transparent and a 1.0 means fully opaque.
• dur : float, default 1.0 Animation duration in seconds.

Here is an example:

theta = [2*m.pi*n/(100 - 1) for n in range(100)]
stroke = [0.5 + 0.3*m.sin(2*t) for t in theta]
color = [(cl(t) << 16) +
        (cl(t - 120*m.pi/180) << 8) +
        (cl(t + 120*m.pi/180)) for t in theta]
alpha = [0.6 + 0.4*m.cos(6*t) for t in theta]
tri = avg.shape([-1.0, 1.0, 0.0, -1.0], [-0.866, -0.866, 0.866, -0.866],
        stroke=stroke, color=color, alpha=alpha, dur=10)

In this example, the stroke, color, and alpha have all been made to change over the period of 10 seconds. The cl( ) is just a custom triangle function.

Frames

Second, place shapes or other frames into frames. The frame class provides the following initialization parameters:

• objs : shape or frame or list of such A single shape or frame object or a list of such objects.
• x : float or array_like, default 0.0 x-axis values of translation of the objects within the frame.
• y : float or array_like, default 0.0 y-axis values of translation of the objects within the frame.
• ang : float or array_like, default 0.0 Angles of rotation of the objects within the frame in degrees.
• scale : float or array_like, default 1.0 Scaling factors of the objects within the frame.
• dur : float, default 1.0 Animation duration in seconds.

Here is an example:

x = [2*m.sin(3*t) for t in theta]
y = [-m.cos(3*t) for t in theta]
ang = [-3*t*180/m.pi for t in theta]
scale = [1 + 0.5*m.sin(2*t) for t in theta]
frm = avg.frame(tri, x, y, ang, scale, dur=10)

So, the tri shape will move to the postions (x, y), rotate to the angles ang, and scale by scale. You can put multiple shapes and frames into another frame. Suppose a and b are shapes and C, D, and E are frames. These can be put into another frame as follows:

frm = avg.frame([a, b, C, D, E], x, y, dur=10)

Animate

When you have finished defining all your shapes and frames, you can create the animation file using the animate function. This function takes the following paramters:

• obj : shape object, frame object, or list of such objects The data to create an animation.
• filename : string, default 'ani.svg' The desired name of output file. End it with '.svg' in order for your system to know which application to use to open it.
• x_lim : array, default [-1, 1] A list of the minimum and maximum x values to display in the animation.
• y_lim : array, default [-1, 1] A list of the minimum and maximum y values to display in the animation.
• width : float, default 640 Desired width of the animation image in pixels. This is also used in determining the scaling factor for the dimensions of the image. If not specified, the image will actually automatically scale to fit the size of the browser window.
• progress : bool, default False Flag to show progress bar.

Here is an example:

avg.animate(frm, x_lim=[-3, 3], y_lim=[-3, 3])

Note that not specifying the width will make the image scale to the size of its container, like the browser window. However, it also means that parts of the animation can sometimes be viewable outside the limits specified.