GraphicsBase scale_x_from_center and scale_y_from_center interfaces¶

This page explains the GraphicsBase class (base class of each graphic, such as the Rectangle) scale_x_from_center and scale_y_from_center property interfaces.

What interfaces are these?¶

The scale_x_from_center property changes the object’s horizontal scale, and the scale_y_from_center property changes the object’s vertical scale. These scaling interfaces change the scale from the center coordinates of each object.

Basic usage¶

Each property getter interface returns a Number value. The setter interfaces also require a Number to update scales (If 0.0 is specified, the object becomes invisible. 1.0 becomes the default scale, and 2.0 becomes the twice-scale value).

The following example shows the default scale rectangle (left), horizontally half-scaled rectangle (center), vertically half-scaled rectangle (right).

import apysc as ap

ap.Stage(
    stage_width=350,
    stage_height=150,
    background_color=ap.Color("#333"),
    stage_elem_id="stage",
)
sprite: ap.Sprite = ap.Sprite()
sprite.graphics.begin_fill(color=ap.Color("#0af"))

left_rectangle: ap.Rectangle = sprite.graphics.draw_rect(
    x=50, y=50, width=50, height=50
)
center_rectangle: ap.Rectangle = sprite.graphics.draw_rect(
    x=150, y=50, width=50, height=50
)
center_rectangle.scale_x_from_center = ap.Number(0.5)
right_rectangle: ap.Rectangle = sprite.graphics.draw_rect(
    x=250, y=50, width=50, height=50
)
right_rectangle.scale_y_from_center = ap.Number(0.5)

ap.save_overall_html(dest_dir_path="graphics_base_scale_from_center_basic_usage_1/")

These interfaces apply the scaling from the center coordinates as follows:

import apysc as ap

ap.Stage(
    stage_width=150,
    stage_height=150,
    background_color=ap.Color("#333"),
    stage_elem_id="stage",
)
sprite: ap.Sprite = ap.Sprite()
sprite.graphics.begin_fill(color=ap.Color("#0af"), alpha=0.3)

rectangle_1: ap.Rectangle = sprite.graphics.draw_rect(x=50, y=50, width=50, height=50)

rectangle_2: ap.Rectangle = sprite.graphics.draw_rect(x=50, y=50, width=50, height=50)
rectangle_2.scale_x_from_center = ap.Number(0.5)
rectangle_2.scale_y_from_center = ap.Number(0.5)

rectangle_3: ap.Rectangle = sprite.graphics.draw_rect(x=50, y=50, width=50, height=50)
rectangle_3.scale_x_from_center = ap.Number(0.25)
rectangle_3.scale_y_from_center = ap.Number(0.25)

ap.save_overall_html(dest_dir_path="graphics_base_scale_from_center_basic_usage_2/")

The += and -= operators are also supported:

from typing_extensions import TypedDict

import apysc as ap


class _RectanglesOptions(TypedDict):
    rectangle_1: ap.Rectangle
    rectangle_2: ap.Rectangle
    direction: ap.Int


def on_timer(e: ap.TimerEvent, options: _RectanglesOptions) -> None:
    """
    The handler that the timer calls.

    Parameters
    ----------
    e : ap.TimerEvent
        Event instance.
    options : dict
        Optional arguments dictionary.
    """
    rectangle_1: ap.Rectangle = options["rectangle_1"]
    rectangle_2: ap.Rectangle = options["rectangle_2"]
    direction: ap.Int = options["direction"]

    current_scale: ap.Number = rectangle_1.scale_x_from_center
    condition_1: ap.Boolean = current_scale >= 2.0
    condition_2: ap.Boolean = current_scale <= 0.05
    with ap.If(condition_1):
        direction.value = -1
    with ap.Elif(condition_2):
        direction.value = 1

    rectangle_1.scale_x_from_center += direction * 0.03
    rectangle_2.scale_y_from_center += direction * 0.03


ap.Stage(
    stage_width=150,
    stage_height=150,
    background_color=ap.Color("#333"),
    stage_elem_id="stage",
)
sprite: ap.Sprite = ap.Sprite()

sprite.graphics.begin_fill(color=ap.Color("#0af"), alpha=0.5)
rectangle_1: ap.Rectangle = sprite.graphics.draw_rect(x=50, y=50, width=50, height=50)

sprite.graphics.begin_fill(color=ap.Color("#f0a"), alpha=0.5)
rectangle_2: ap.Rectangle = sprite.graphics.draw_rect(x=50, y=50, width=50, height=50)


direction: ap.Int = ap.Int(1.0)
options: _RectanglesOptions = {
    "rectangle_1": rectangle_1,
    "rectangle_2": rectangle_2,
    "direction": direction,
}
timer: ap.Timer = ap.Timer(on_timer, delay=ap.FPS.FPS_60, options=options)
timer.start()

ap.save_overall_html(dest_dir_path="graphics_base_scale_from_center_basic_usage_3/")

scale_x_from_center property API¶

Note: the document build script generates and updates this API document section automatically. Maybe this section is duplicated compared with previous sections.

[Interface summary]

Get a scale-x value from the center of this instance.

[Returns]

scale_x_from_center: ap.Number
- Scale-x value from the center of this instance.

[Notes]

The scale’s minimum value is almost zero, and it does not become negative.

[Examples]

>>> import apysc as ap
>>> stage: ap.Stage = ap.Stage()
>>> sprite: ap.Sprite = ap.Sprite()
>>> sprite.graphics.begin_fill(color=ap.Color("#0af"))
>>> rectangle: ap.Rectangle = sprite.graphics.draw_rect(
...     x=50, y=50, width=50, height=50
... )
>>> rectangle.scale_x_from_center = ap.Number(1.5)
>>> rectangle.scale_x_from_center
Number(1.5)

scale_y_from_center property API¶