lqr_carver_bias_set_energy_function — set a custom energy function for a LqrCarver object
#include <lqr.h>
LqrRetVal lqr_carver_set_energy_function( | LqrCarver* carver, |
| LqrEnergyFunc en_func, | |
| gint radius, | |
| LqrEnergyReaderType reader_type, | |
gpointer extra_data); |
The function lqr_carver_set_energy_function assigns the energy function
en_func to the LqrCarver object pointed to by
carver (see below for more details on custom functions definitions).
The parameter radius determines the size of the square region which
affects the computation around each pixel (the side of the square will be 2 *
pixels long).
radius + 1
The parameter reader_type sets the reader type used when reading the
image, and therefore it determines what quantity will be passed on to the function
en_func (see below for more details on reader types).
The parameter extra_data is a (void) pointer which can be used to pass on
additional values to the function ef_func.
The function en_func must be of type
LqrEnergyFunc, whose prototype is defined by:
typedef gfloat (*LqrEnergyFunc) (gint x, gint y, gint img_width, gint img_height, LqrReadingWindow * rwindow, gpointer extra_data);
Such a function is expected to compute the energy at pixel x, y based on the
knowledge of the current image size (obtained from width and height) and the content of
the image in a square around that pixel, which is passed through the
rwindow reading window.
In most cases, the parameters x, y, width and height would only be used
to determine whether the region under consideration is at the image boundary or not.
The rwindow content must be read using the function
lqr_rwindow_read(3).
The LqrEnergyReaderType is an enum which can take these values
(also noted is the number of channels of the corresponging reading window):
LQR_ER_BRIGHTNESSbrightness (1 channel)
LQR_ER_BRIGHTNESSluma (1 channel)
LQR_ER_RGBARGBA (4 channels)
LQR_ER_CUSTOMread the normalised image channels as they are (as many channels as the image has)
These readouts always return values beetween 0 and 1.
Note that these readouts may have special meanings depending on the image type:
for LQR_GREY_IMAGE, LQR_GREYA_IMAGE and
LQR_CUSTOM_IMAGE images, the LQR_ER_LUMA
readout will yield the same result as LQR_ER_BRIGHTNESS
for LQR_CUSTOM_IMAGE images, the LQR_ER_BRIGHTNESS
readout will return the average pixel value (additive, i.e. if a black channel is
present the channel values will be inverted and multiplied by the black channel
inverse), multiplied by the alpha channel value.
for LQR_CUSTOM_IMAGE images, the LQR_ER_RGBA
readout cannot be used: it will always return
0