Fade Keyframe

Keyframe for transitioning between two or more colors. More...

Data Structures
struct	point_t
	Single point on a cartesian plane. More...
struct	cubic_bezier_t
	Pair of control points for a cubic bezier curve where the start is (0,0) and end is (1,1). More...
struct	keyframe_fade_t
	Fade keyframe. More...

Macros
#define	KEYFRAME_FADE_COLORS_INPUT_MAX_LENGTH   (15)
	Maximum number of colors allowed to be input by the user.
#define	KEYFRAME_FADE_COLORS_MAX_LENGTH   (KEYFRAME_FADE_COLORS_INPUT_MAX_LENGTH + 1)
	Maximum number of colors that can be faded in one keyframe. More...

Enumerations
enum	fade_type_t { FADE_TYPE_STEP , FADE_TYPE_CUBIC }
	The type of fade to perform. More...
enum	fade_axis_t { FADE_AXIS_NONE = 0 , FADE_AXIS_HUE = (1U << 0) , FADE_AXIS_SAT = (1U << 1) , FADE_AXIS_VAL = (1U << 2) }
	The color axes/channels to fade over. More...

Functions
static bool	keyframe_fade_render_frame (keyframe_base_t *const p_keyframe, timestep_t time, color_rgb_t *p_color_out)
static void	keyframe_fade_render_init (keyframe_base_t *const p_keyframe, framerate_t framerate, color_rgb_t current_color)
static keyframe_base_t *	keyframe_fade_clone (keyframe_base_t const *const p_keyframe)
static void	blend_colors (color_hsv_t const *p_a, color_hsv_t const *p_b, fade_axis_t axis, float ratio, color_hsv_t *p_out)
	Blends two HSV colors based on a ratio between a to b. More...
static void	cubic_bezier_calc (cubic_bezier_t const *const p_curve, float t, point_t *p_point)
	Calculates a point on a cubic bezier curve at interpolation index, t. More...
keyframe_base_t *	keyframe_fade_parse (char *p_str)
	Parses a command string into a Fade Keyframe. More...
keyframe_base_t *	keyframe_fade_ctor (keyframe_fade_t *p_fade)
	Initialize a Fade keyframe with the appropriate keyframe_base_t and state values. More...

Variables
static const keyframe_base_api_t	keyframe_fade_api
	Fade keyframe API function pointers. More...
static const keyframe_fade_t	keyframe_fade_init
	Default values for fade keyframe structs. More...
const cubic_bezier_t	cb_linear = { { 0.0f, 0.0f }, { 1.0f, 1.0f } }
	Control points for linear fade. More...
const cubic_bezier_t	cb_ease = { { 0.25f, 0.1f }, { 0.25f, 1.0f } }
	Control points for ease fade. More...
const cubic_bezier_t	cb_ease_in = { { 0.42f, 0.0f }, { 1.0f, 1.0f } }
	Control points for ease-in fade. More...
const cubic_bezier_t	cb_ease_out = { { 0.0f, 0.0f }, { 0.58f, 1.0f } }
	Control points for ease-out fade. More...
const cubic_bezier_t	cb_ease_in_out = { { 0.42f, 0.0f }, { 0.58f, 1.0f } }
	Control points for ease-in-out fade. More...
const cubic_bezier_t	cb_linear
	Control points for linear fade. More...
const cubic_bezier_t	cb_ease
	Control points for ease fade. More...
const cubic_bezier_t	cb_ease_in
	Control points for ease-in fade. More...
const cubic_bezier_t	cb_ease_out
	Control points for ease-out fade. More...
const cubic_bezier_t	cb_ease_in_out
	Control points for ease-in-out fade. More...

Detailed Description

Keyframe for transitioning between two or more colors.

Macro Definition Documentation

KEYFRAME_FADE_COLORS_MAX_LENGTH

#define KEYFRAME_FADE_COLORS_MAX_LENGTH   (KEYFRAME_FADE_COLORS_INPUT_MAX_LENGTH + 1)

Maximum number of colors that can be faded in one keyframe.

Input + 1 to allow current color to be pushed to the top.

Enumeration Type Documentation

fade_axis_t

enum fade_axis_t

The color axes/channels to fade over.

Enumerator
FADE_AXIS_NONE	No axis require fading.
FADE_AXIS_HUE	Fade is needed for the Hue axis.
FADE_AXIS_SAT	Fade is needed for the Saturation axis.
FADE_AXIS_VAL	Fade if needed for the Value axis.

fade_type_t

enum fade_type_t

The type of fade to perform.

Enumerator
FADE_TYPE_STEP	Colors are immediately transitioned.
FADE_TYPE_CUBIC	The transition curve is applied between every pair of colors.

Function Documentation

blend_colors()

static void blend_colors ( color_hsv_t const *  p_a, color_hsv_t const *  p_b, fade_axis_t  axis, float  ratio, color_hsv_t *  p_out  )

static

Blends two HSV colors based on a ratio between a to b.

Parameters

[in]	p_a	Pointer to color a (ratio = 0).
[in]	p_b	Pointer to color b (ratio = 1).
	axis	The axes to blend across.
	ratio	The ratio between color a and color b.
[out]	p_out	Pointer to store the blended color.

cubic_bezier_calc()

static void cubic_bezier_calc ( cubic_bezier_t const *const  p_curve, float  t, point_t *  p_point  )

static

Calculates a point on a cubic bezier curve at interpolation index, t.

This function assumes start, \( P_0 \), and end, \( P_3 \), points of \( (0,0) \) and \( (1,1) \) respectively. The equation for the bezier curve is

\[ \vec{B}(t) = (1-t)^3 \vec{P}_0 + 3 (1-t)^2 t \vec{P}_1 + 3 (1-t) t^2 \vec{P}_2 + t^3 \vec{P}_3, \quad 0 \le t \le 1 \]

or simplified using the assumptions for \( P_0 \) and \( P_3 \)

\[ \vec{B}(t) = 3 (1-t)^2 t \vec{P}_1 + 3 (1-t) t^2 \vec{P}_2 + t^3, \quad 0 \le t \le 1 \]

Parameters

[in]	p_curve	Pointer to the bezier control points.
	t	Interpolation index at which to calculate a point on the curve; 0 <= t <= 1.
[out]	p_point	Pointer to store the calculated point.

keyframe_fade_ctor()

keyframe_base_t * keyframe_fade_ctor

(

keyframe_fade_t *

p_fade

)

Initialize a Fade keyframe with the appropriate keyframe_base_t and state values.

Parameters

[in]

p_fade

Pointer to the fade keyframe to construct, or NULL to allocate a new one.

Returns

Pointer to the keyframe base portion of the fade keyframe.

keyframe_fade_parse()

keyframe_base_t * keyframe_fade_parse

(

char *

p_str

)

Parses a command string into a Fade Keyframe.

Parameters

[in]

p_str

Pointer to the command string.

Returns

Pointer to the parsed keyframe or NULL on error.

Variable Documentation

cb_ease [1/2]

const cubic_bezier_t cb_ease = { { 0.25f, 0.1f }, { 0.25f, 1.0f } }

Control points for ease fade.

Quickly fades from the start value, then transitions slower to the end value.

cb_ease [2/2]

const cubic_bezier_t cb_ease

extern

Control points for ease fade.

Quickly fades from the start value, then transitions slower to the end value.

cb_ease_in [1/2]

const cubic_bezier_t cb_ease_in = { { 0.42f, 0.0f }, { 1.0f, 1.0f } }

Control points for ease-in fade.

Slow fade at the start then quickly fades to the end value.

cb_ease_in [2/2]

const cubic_bezier_t cb_ease_in

extern

Control points for ease-in fade.

Slow fade at the start then quickly fades to the end value.

cb_ease_in_out [1/2]

const cubic_bezier_t cb_ease_in_out = { { 0.42f, 0.0f }, { 0.58f, 1.0f } }

Control points for ease-in-out fade.

Quickly transitions from the start to the end; faster than normal ease.

cb_ease_in_out [2/2]

const cubic_bezier_t cb_ease_in_out

extern

Control points for ease-in-out fade.

Quickly transitions from the start to the end; faster than normal ease.

cb_ease_out [1/2]

const cubic_bezier_t cb_ease_out = { { 0.0f, 0.0f }, { 0.58f, 1.0f } }

Control points for ease-out fade.

Quickly fades from the start value then slowly fades to the end value.

cb_ease_out [2/2]

const cubic_bezier_t cb_ease_out

extern

Control points for ease-out fade.

Quickly fades from the start value then slowly fades to the end value.

cb_linear [1/2]

const cubic_bezier_t cb_linear = { { 0.0f, 0.0f }, { 1.0f, 1.0f } }

Control points for linear fade.

Fades linearly, in equal steps, between the start and end values.

cb_linear [2/2]

const cubic_bezier_t cb_linear

extern

Control points for linear fade.

Fades linearly, in equal steps, between the start and end values.

keyframe_fade_api

const keyframe_base_api_t keyframe_fade_api

static

Initial value:

=
{
    .render_frame = keyframe_fade_render_frame,
    .render_init = keyframe_fade_render_init,
    .clone = keyframe_fade_clone,
}

Fade keyframe API function pointers.

keyframe_fade_init

const keyframe_fade_t keyframe_fade_init

static

Initial value:

= 
{
    .base = { .p_api = &keyframe_fade_api },
    .args =
    {
        .colors_len = 0,
        .push_current = false,
        .fade_type = FADE_TYPE_CUBIC,
        .curve = { { 0.0f,  0.0f }, { 1.0f,  1.0f } },  
        .period = 1
    }
}

Default values for fade keyframe structs.