ACE automatic color enhancement. More...

Functions
int	ace_enhance_image_interp (float u, const float f, int width, int height, float alpha, const char *omega_string, int num_levels)
	ACE automatic color enhancement using level interpolation. More...

int	ace_enhance_image_poly (float u, const float f, int width, int height, float alpha, const char *omega_string, int degree)
	ACE automatic color enhancement using a polynomial slope function. More...

Detailed Description

ACE automatic color enhancement.

Author: Pascal Getreuer getre.nosp@m.uer@.nosp@m.gmail.nosp@m..com

This program is free software: you can redistribute it and/or modify it under, at your option, the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version, or the terms of the simplified BSD license.

You should have received a copy of these licenses along with this program. If not, see http://www.gnu.org/licenses/ and http://www.opensource.org/licenses/bsd-license.html.

Definition in file ace.h.

Function Documentation

int ace_enhance_image_interp	(	float *	u,
		const float *	f,
		int	width,
		int	height,
		float	alpha,
		const char *	omega_string,
		int	num_levels
	)

ACE automatic color enhancement using level interpolation.

Parameters

u	the enhanced output image
f	the input image in planar row-major order
width,height	image dimensions
alpha	the slope parameter (>=1), larger implies stronger enhancement
omega_string	string specifying the spatial weighting function
num_levels	number of interpolation levels (>=2)

Returns: 1 on success, 0 on failure

This routine perform ACE enhancement by computing

$\omega(x) * s_\alpha(L - I(x))$

for fixed levels L. The $ R_L $ are then piecewise linearly interpolated to approximate R. The parameter num_levels determines the number of L values used. Increasing num_levels improves quality but increases computation time.

If non-null, parameter omega_string specifies the spatial weighting function $\omega(x,y)$ . Valid choices are

"1/r" default ACE, $\omega(x,y) = 1/\sqrt{x^2 + y^2}$
"1" constant, $\omega(x,y) = 1$
"G:#" Gaussian where # is a number specifying $\sigma$ , $\omega(x,y) = \exp(-\tfrac{x^2 + y^2}{2\sigma^2})$

If OpenMP is enabled, the main computation loop is parallelized.

Definition at line 78 of file ace.c.

int ace_enhance_image_poly	(	float *	u,
		const float *	f,
		int	width,
		int	height,
		float	alpha,
		const char *	omega_string,
		int	degree
	)

ACE automatic color enhancement using a polynomial slope function.

Parameters

u	the enhanced output image
f	the input image in planar row-major order
width,height	image dimensions
alpha	the slope parameter (>=1), larger implies stronger enhancement
omega_string	string specifying the spatial weighting function
degree	polynomial degree (can be 3, 5, 7, 9, or 11)

Returns: 1 on success, 0 on failure

This routine perform ACE enhancement using the fast O(N log N) algorithm of Bertalmio et al. The slope parameter must be an integer or half-integer between 1 and 8 (1, 1.5, 2, 2.5, ..., 7.5, 8). The slope function is approximated by an $L^\infty$ -optimal polynomial of degree degree.

If non-null, parameter omega_string specifies the spatial weighting function $\omega(x,y)$ . Valid choices are

"1/r" default ACE, $\omega(x,y) = 1/\sqrt{x^2 + y^2}$
"1" constant, $\omega(x,y) = 1$
"G:#" Gaussian where # is a number specifying $\sigma$ , $\omega(x,y) = \exp(-\tfrac{x^2 + y^2}{2\sigma^2})$

If OpenMP is enabled, the main computation loop is parallelized.

note: In the parallel computation, values are summed in a nondeterministic order (i.e., in whichever order threads complete). Due to rounding effects, addition is not exactly associative and the output varies slightly between runs (+/- 1 intensity level).

Definition at line 266 of file ace.c.

Functions

Detailed Description

Function Documentation