% o exception: return any errors or warnings in this structure.
%
*/
-MagickExport MagickBooleanType SigmoidalContrastImage(Image *image,
- const MagickBooleanType sharpen,const double contrast,const double midpoint,
- ExceptionInfo *exception)
-{
-#define SigmoidalContrastImageTag "SigmoidalContrast/Image"
-
- CacheView
- *image_view;
-
- MagickBooleanType
- status;
-
- MagickOffsetType
- progress;
-
- ssize_t
- y;
-
- /*
- Side effect: clamps values unless contrast<MagickEpsilon, in which
- case nothing is done.
- */
- if (contrast<MagickEpsilon)
- return(MagickTrue);
/*
Sigmoidal function with inflexion point moved to b and "slope
#else
#define Sigmoidal(a,b,x) ( 1.0/(1.0+exp((a)*((b)-(x)))) )
#endif
- /*
- Scaled sigmoidal formula:
+/*
+ Scaled sigmoidal formula:
+
( Sigmoidal(a,b,x) - Sigmoidal(a,b,0) ) /
( Sigmoidal(a,b,1) - Sigmoidal(a,b,0) )
- See http://osdir.com/ml/video.image-magick.devel/2005-04/msg00006.html
- and http://www.cs.dartmouth.edu/farid/downloads/tutorials/fip.pdf.
- The limit of ScaledSigmoidal as a->0 is the identity, but a=0 gives a
- division by zero. This is fixed above by exiting immediately when
- contrast is small, leaving the image (or colormap) unmodified. This
- appears to be safe because the series expansion of the logistic
- sigmoidal function around x=b is 1/2-a*(b-x)/4+... so that the key
- denominator s(1)-s(0) is about a/4 (a/2 with tanh).
- */
+
+ See http://osdir.com/ml/video.image-magick.devel/2005-04/msg00006.html and
+ http://www.cs.dartmouth.edu/farid/downloads/tutorials/fip.pdf. The limit
+ of ScaledSigmoidal as a->0 is the identity, but a=0 gives a division by
+ zero. This is fixed above by exiting immediately when contrast is small,
+ leaving the image (or colormap) unmodified. This appears to be safe because
+ the series expansion of the logistic sigmoidal function around x=b is
+ 1/2-a*(b-x)/4+... so that the key denominator s(1)-s(0) is about a/4
+ (a/2 with tanh).
+*/
#define ScaledSigmoidal(a,b,x) ( \
(Sigmoidal((a),(b),(x))-Sigmoidal((a),(b),0.0)) / \
(Sigmoidal((a),(b),1.0)-Sigmoidal((a),(b),0.0)) )
- /*
- Inverse of ScaledSigmoidal, used for +sigmoidal-contrast.
- Because b may be 0 or 1, the argument of the hyperbolic tangent
- (resp. logistic sigmoidal) may be outside of the interval (-1,1)
- (resp. (0,1)), even when creating a LUT, hence the branching.
- In addition, HDRI may have out of gamut values.
- InverseScaledSigmoidal is not a two-side inverse of
- ScaledSigmoidal: It is only a right inverse. This is unavoidable.
- */
+/*
+ Inverse of ScaledSigmoidal, used for +sigmoidal-contrast. Because b may be
+ 0 or 1, the argument of the hyperbolic tangent (resp. logistic sigmoidal)
+ may be outside of the interval (-1,1) (resp. (0,1)), even when creating a
+ LUT, hence the branching. In addition, HDRI may have out of gamut values.
+ InverseScaledSigmoidal is not a two-side inverse of ScaledSigmoidal:
+ It is only a right inverse. This is unavoidable.
+*/
#if defined(MAGICKCORE_HAVE_ATANH)
-#define InverseScaledSigmoidal(a,b,x) ({ \
- const double _argument = \
- (Sigmoidal((a),(b),1.0)-Sigmoidal((a),(b),0.0)) * (x) + \
- Sigmoidal((a),(b),0.0); \
- const double _clamped_argument = \
- ( _argument < -1+MagickEpsilon ? -1+MagickEpsilon : \
- ( _argument > 1-MagickEpsilon ? 1-MagickEpsilon : _argument ) ); \
- (b) + (2.0/(a)) * atanh(_clamped_argument); })
+static inline double InverseScaledSigmoidal(const double a,const double b,
+ const double x)
+{
+ const double _argument =
+ (Sigmoidal((a),(b),1.0)-Sigmoidal((a),(b),0.0)) * (x) +
+ Sigmoidal((a),(b),0.0);
+
+ const double _clamped_argument =
+ ( _argument < -1+MagickEpsilon ? -1+MagickEpsilon :
+ ( _argument > 1-MagickEpsilon ? 1-MagickEpsilon : _argument ) );
+
+ return((b) + (2.0/(a)) * atanh(_clamped_argument));
+}
#else
-#define InverseScaledSigmoidal(a,b,x) ({ \
- const double _argument = \
- (Sigmoidal((a),(b),1.0)-Sigmoidal((a),(b),0.0)) * (x) + \
- Sigmoidal((a),(b),0.0); \
- const double _clamped_argument = \
- ( _argument < MagickEpsilon ? MagickEpsilon : \
- ( _argument > 1-MagickEpsilon ? 1-MagickEpsilon : _argument ) ); \
- (b) + (-1.0/(a)) * log(1.0/_clamped_argument+-1.0); })
+static inline double InverseScaledSigmoidal(const double a,const double b,
+ const double x)
+{
+ const double _argument =
+ (Sigmoidal((a),(b),1.0)-Sigmoidal((a),(b),0.0)) * (x) +
+ Sigmoidal((a),(b),0.0);
+
+ const double _clamped_argument =
+ ( _argument < MagickEpsilon ? MagickEpsilon :
+ ( _argument > 1-MagickEpsilon ? 1-MagickEpsilon : _argument ) );
+
+ return((b) + (-1.0/(a)) * log(1.0/_clamped_argument+-1.0));
+}
#endif
- /*
- Convenience macros.
- */
+
+MagickExport MagickBooleanType SigmoidalContrastImage(Image *image,
+ const MagickBooleanType sharpen,const double contrast,const double midpoint,
+ ExceptionInfo *exception)
+{
+#define SigmoidalContrastImageTag "SigmoidalContrast/Image"
#define ScaledSig(x) ( ClampToQuantum(QuantumRange* \
ScaledSigmoidal(contrast,QuantumScale*midpoint,QuantumScale*(x))) )
#define InverseScaledSig(x) ( ClampToQuantum(QuantumRange* \
InverseScaledSigmoidal(contrast,QuantumScale*midpoint,QuantumScale*(x))) )
+ CacheView
+ *image_view;
+
+ MagickBooleanType
+ status;
+
+ MagickOffsetType
+ progress;
+
+ ssize_t
+ y;
+
+ /*
+ Convenience macros.
+ */
assert(image != (Image *) NULL);
assert(image->signature == MagickSignature);
if (image->debug != MagickFalse)
(void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
+ /*
+ Side effect: clamps values unless contrast<MagickEpsilon, in which
+ case nothing is done.
+ */
+ if (contrast < MagickEpsilon)
+ return(MagickTrue);
/*
Sigmoidal-contrast enhance colormap.
*/
projects / imagemagick / commitdiff