Image transformation
[Video]

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 ()
	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.

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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.

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Typedef Documentation

typedef struct gavl_image_transform_s gavl_image_transform_t

Opaque image transformation engine.

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

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 dimesion to signal that a pixel is outside the source image.

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Function Documentation

GAVL_PUBLIC gavl_image_transform_t* gavl_image_transform_create

(

)

Create a transformation engine.

Returns:

A newly allocated transformation engine

Since 1.1.0.

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.

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 sucessfully 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.

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.

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.