Image transformation

Typedefs
typedef struct gavl_image_transform_s	gavl_image_transform_t
	Opaque image transformation engine.
typedef void(*)	gavl_image_transform_func(void *priv, double xdst, double ydst, double *xsrc, double *ysrc)
	Function describing the method.

Functions
GAVL_PUBLIC gavl_image_transform_t *	gavl_image_transform_create (void)
	Create a transformation engine.
GAVL_PUBLIC void	gavl_image_transform_destroy (gavl_image_transform_t *t)
	Destroy a transformation engine.
GAVL_PUBLIC int	gavl_image_transform_init (gavl_image_transform_t *t, gavl_video_format_t *format, gavl_image_transform_func func, void *priv)
	Initialize a transformation engine.
GAVL_PUBLIC void	gavl_image_transform_transform (gavl_image_transform_t *t, gavl_video_frame_t *in_frame, gavl_video_frame_t *out_frame)
	Transform an image.
GAVL_PUBLIC gavl_video_options_t *	gavl_image_transform_get_options (gavl_image_transform_t *t)
	Get transformation options.

Detailed Description

gavl includes a generic image transformation engine. You pass a function pointer to the init function, which transforms the destination coordinates into source coordinates.

The interpolation method is set with gavl_video_options_set_scale_mode, but not all modes are supported. When initialized with an invalid scale mode, the transformation engine will silently choose the closest one.

Typedef Documentation

gavl_image_transform_t

typedef struct gavl_image_transform_s gavl_image_transform_t

Opaque image transformation engine.

You don't want to know what's inside.

gavl_image_transform_func

typedef void(*) gavl_image_transform_func(void *priv, double xdst, double ydst, double *xsrc, double *ysrc)

Function describing the method.

Parameters

priv	User data
xdst	X-coordinate of the destination
ydst	Y-coordinate of the destination
xsrc	Returns X-coordinate of the source
ysrc	Returns Y-coordinate of the source

All coordinates are in fractional pixels. 0,0 is the upper left corner. Return negative values or values larger than the dimension to signal that a pixel is outside the source image.

Function Documentation

gavl_image_transform_create()

GAVL_PUBLIC gavl_image_transform_t * gavl_image_transform_create

(

void

)

Create a transformation engine.

Returns

A newly allocated transformation engine

Since 1.1.0.

References gavl_image_transform_create().

Referenced by gavl_image_transform_create().

gavl_image_transform_destroy()

GAVL_PUBLIC void gavl_image_transform_destroy

(

gavl_image_transform_t *

t

)

Destroy a transformation engine.

Parameters

t	A transformation engine Since 1.1.0.

References gavl_image_transform_destroy().

Referenced by gavl_image_transform_destroy().

gavl_image_transform_init()

GAVL_PUBLIC int gavl_image_transform_init	(	gavl_image_transform_t *	t,
		gavl_video_format_t *	format,
		gavl_image_transform_func	func,
		void *	priv )

Initialize a transformation engine.

Parameters

t	A transformation engine
format	Format (can be changed)
func	Coordinate transform function
priv	The priv argument for func

Returns

1 if the transform was successfully initialized, 0 else.

If you enabled multithreading support, func will be called from multiple threads at the same time. Make sure, that it doesn't access any global data.

Return type was changed from void to in in version 1.1.2 Under normal circumstances, this function always returns 1.

Since 1.1.0.

References gavl_image_transform_init().

Referenced by gavl_image_transform_init().

gavl_image_transform_transform()

GAVL_PUBLIC void gavl_image_transform_transform	(	gavl_image_transform_t *	t,
		gavl_video_frame_t *	in_frame,
		gavl_video_frame_t *	out_frame )

Transform an image.

Parameters

t	A transformation engine
in_frame	Input frame
out_frame	Output frame Since 1.1.0.

References gavl_image_transform_transform().

Referenced by gavl_image_transform_transform().

gavl_image_transform_get_options()

GAVL_PUBLIC gavl_video_options_t * gavl_image_transform_get_options

(

gavl_image_transform_t *

t

)

Get transformation options.

Parameters

t	A transformation engine

Returns

Options

After you called this, you can use the gavl_video_options_set_*() functions to change the options. Options will become valid with the next call to gavl_image_transform_init.

Since 1.1.0.

References gavl_image_transform_get_options().

Referenced by gavl_image_transform_get_options().