Module genpygoodies.formula

The formula module provides some utility functions and classes for creating formulas that appear and disappear in specific locations.

The code converts a formula from Latex to a PNG image that is then rendered as an image. The conversion is relatively time-consuming (typically it takes a few seconds). When making movies is best to avoid creating formulas per frame, if possible. It is better to create a formula image just once outside the draw function.

Functions

def make_formulas_png(filepath, formulas, color, dpi=600, gap=50, background=<generativepy.color.Color object>, packages=None)

Create a PNG image of a list of latex formulas.

The formulas will be left aligned. The image will be sized so that there is a border of gap pixels around the formulas in the final image. If there is more than one formula, each will be separated by gap pixels horizontally

Parameters

  • formulas: list of str - Latex formula
  • color: Color - Colour of formula.
  • dpi: number - Controls formula size. See formula module of generativepy documentation.
  • gap: number - Controls the width of the border around the edge of the formulas, and also the horizontal gap between the formulas.
  • packages: sequence of str - tuple containing any required additional latex packages

Returns

A tuple (width, height) indicating the pixel size of the final image.

Classes

class formula_fade_in (formula, position, color, appear_time=0, appear_duration=1, dpi=600, disappear_time=None, fade_duration=1)

Displays a formula with a fade animation. FADE IS NOT YET IMPLEMENTED see usage.

Parameters

  • formula: str - Latex formula
  • position: (number, number) - Tuple giving position of centre of formula
  • color: Color - Colour of formula.
  • appear_time: number - Time in seconds when formula appears and zoom starts.
  • appear_duration: number - Duration for formula to fade in. See usage.
  • dpi: number - Controls formula size. See formula module of generativepy documentation.
  • disappear_time: number - Time in seconds when formula starts to fade. Default None formula stays visible forever,
  • fade_duration: number - Duration for formula to fade out. See usage.
  • packages: sequence of str - list of names of Latex packages the formula uses.

Returns

A configured formula_fade_in object.

Usage Fading is not currently implemented. The formula will always be visible. The description below is for the intended behaviour when it is fully implemented.

This class displays a formula that fades in at a certain time. It is best to have an understanding of the generativepy formula module before attempting to use this class. It will explain important details such as the dpi and packages parameters.

Expand source code 
class formula_fade_in():

    def __init__(self, formula, position, color, appear_time=0, appear_duration=1, dpi=600, disappear_time=None, fade_duration=1):
        """
        Displays a formula with a fade animation. FADE IS NOT YET IMPLEMENTED see usage.

        **Parameters**

        * `formula`: str - Latex formula
        * `position`: (number, number) - Tuple giving position of centre of formula
        * `color`: Color - Colour of formula.
        * `appear_time`: number - Time in seconds when formula appears and zoom starts.
        * `appear_duration`: number - Duration for formula to fade in. See usage.
        * `dpi`: number - Controls formula size. See formula module of generativepy documentation.
        * `disappear_time`: number - Time in seconds when formula starts to fade. Default `None` formula stays visible forever,
        * `fade_duration`: number - Duration for formula to fade out. See usage.
        * `packages`: sequence of str - list of names of Latex packages the `formula` uses.

        **Returns**

        A configured `formula_fade_in` object.

        **Usage**
        Fading is not currently implemented. The formula will always be visible. The description below is for the intended
        behaviour when it is fully implemented.

        This class displays a formula that fades in at a certain time. It is best to have an understanding of the generativepy
        formula module before attempting to use this class. It will explain important details such as the `dpi` and `packages`
        parameters.
        """
        global _FORMULA_INDEX
        name = "formula" + str(_FORMULA_INDEX)
        _FORMULA_INDEX += 1
        self.image, self.size = rasterise_formula(name, formula, color, dpi=dpi)
        self.position = position
        self.alpha = Tween(0).wait(appear_time).to_d(1, appear_duration)
        if disappear_time is not None:
            self.alpha.wait(disappear_time).to_d(0, fade_duration)

    def at(self, position):
        """
        Changes the position of the formula. This is MUCH faster than creating a new formula object.

        **Parameters**

        * `position`: (number, number) - Tuple giving position of centre of formula

        **Returns**

        self

        **Usage**
        This can be used to change the display position of an existing formula after it has been created.

        This is useful if the formula appears in a movie and you need to move the formula around for each frame. It allows
        you to create the formula once and then move it on each frame.
        """
        self.position = position
        return self

    def show(self, ctx, fn):
        """
        Draws the formula in a frame

        **Parameters**

        * `ctx`: drawing context - Context to draw the formula into.
        * `fn`: int - Current frame number.

        **Returns**

        None

        **Usage**
        Call this in the draw function of every frame where the formula should appear.
        """
        # if self.alpha[fn]:
        #     Image(ctx).of_file_position(self.image, self.position)
        Image(ctx).of_file_position(self.image, self.position)

Methods

def at(self, position)

Changes the position of the formula. This is MUCH faster than creating a new formula object.

Parameters

  • position: (number, number) - Tuple giving position of centre of formula

Returns

self

Usage This can be used to change the display position of an existing formula after it has been created.

This is useful if the formula appears in a movie and you need to move the formula around for each frame. It allows you to create the formula once and then move it on each frame.

def show(self, ctx, fn)

Draws the formula in a frame

Parameters

  • ctx: drawing context - Context to draw the formula into.
  • fn: int - Current frame number.

Returns

None

Usage Call this in the draw function of every frame where the formula should appear.

class formula_zoom_in (formula, position, color, appear_time=0, scale_duration=1, initial_scale=0.7, dpi=600, disappear_time=None, fade_duration=1, packages=[])

Displays a formula with a zoom animation.

Parameters

  • formula: str - Latex formula
  • position: (number, number) - Tuple giving position of centre of formula
  • color: Color - Colour of formula.
  • appear_time: number - Time in seconds when formula appears and zoom starts.
  • scale_duration: number - Duration for formula to scale to full size. Default 1.
  • initial_scale: number - Initial size of formula as fraction of full size. Default 0.7
  • dpi: number - Controls formula size. See formula module of generativepy documentation.
  • disappear_time: number - Time in seconds when formula starts to fade. Default None formula stays visible forever,
  • fade_duration: number - Duration for formula to fade out. See usage.
  • packages: sequence of str - list of names of Latex packages the formula uses.

Returns

A configured formula_zoom_in object.

Usage This class displays a formula that zooms in at a certain time. It is best to have an understanding of the generativepy formula module before attempting to use this class. It will explain important details such as the dpi and packages parameters.

Fading is not currently implemented. The formula will behave as if the fade_duration is zero.

Expand source code 
class formula_zoom_in():

    def __init__(self, formula, position, color, appear_time=0, scale_duration=1, initial_scale=0.7, dpi=600, disappear_time=None, fade_duration=1, packages=[]):
        """
        Displays a formula with a zoom animation.

        **Parameters**

        * `formula`: str - Latex formula
        * `position`: (number, number) - Tuple giving position of centre of formula
        * `color`: Color - Colour of formula.
        * `appear_time`: number - Time in seconds when formula appears and zoom starts.
        * `scale_duration`: number - Duration for formula to scale to full size. Default 1.
        * `initial_scale`: number - Initial size of formula as fraction of full size. Default 0.7
        * `dpi`: number - Controls formula size. See formula module of generativepy documentation.
        * `disappear_time`: number - Time in seconds when formula starts to fade. Default `None` formula stays visible forever,
        * `fade_duration`: number - Duration for formula to fade out. See usage.
        * `packages`: sequence of str - list of names of Latex packages the `formula` uses.

        **Returns**

        A configured `formula_zoom_in` object.

        **Usage**
        This class displays a formula that zooms in at a certain time. It is best to have an understanding of the generativepy
        formula module before attempting to use this class. It will explain important details such as the `dpi` and `packages`
        parameters.

        Fading is not currently implemented. The formula will behave as if the `fade_duration` is zero.
        """
        global _FORMULA_INDEX
        name = "formula" + str(_FORMULA_INDEX)
        _FORMULA_INDEX += 1
        self.image, self.size = rasterise_formula(name, formula, color, dpi=dpi, packages=packages)
        self.position = position
        self.scale = Tween(initial_scale).wait(appear_time).to_d(1, scale_duration)
        self.alpha = Tween(0).wait(appear_time).set(1)
        if disappear_time is not None:
            self.alpha.wait(disappear_time).to_d(0, fade_duration)

    def at(self, position):
        """
        Changes the position of the formula. This is MUCH faster than creating a new formula object.

        **Parameters**

        * `position`: (number, number) - Tuple giving position of centre of formula

        **Returns**

        self

        **Usage**
        This can be used to change the display position of an existing formula after it has been created.

        This is useful if the formula appears in a movie and you need to move the formula around for each frame. It allows
        you to create the formula once and then move it on each frame.
        """
        self.position = position
        return self

    def show(self, ctx, fn):
        """
        Draws the formula in a frame

        **Parameters**

        * `ctx`: drawing context - Context to draw the formula into.
        * `fn`: int - Current frame number.

        **Returns**

        None

        **Usage**
        Call this in the draw function of every frame where the formula should appear.
        """
        if self.alpha[fn]:
            Image(ctx).of_file_position(self.image, (self.position[0] - self.size[0] * self.scale[fn] / 2, self.position[1] - self.size[1] * self.scale[fn] / 2)).scale(self.scale[fn]).paint()

Methods

def at(self, position)

Changes the position of the formula. This is MUCH faster than creating a new formula object.

Parameters

  • position: (number, number) - Tuple giving position of centre of formula

Returns

self

Usage This can be used to change the display position of an existing formula after it has been created.

This is useful if the formula appears in a movie and you need to move the formula around for each frame. It allows you to create the formula once and then move it on each frame.

def show(self, ctx, fn)

Draws the formula in a frame

Parameters

  • ctx: drawing context - Context to draw the formula into.
  • fn: int - Current frame number.

Returns

None

Usage Call this in the draw function of every frame where the formula should appear.