Contrast enhance colormap.
*/
for (i=0; i < (ssize_t) image->colors; i++)
- Contrast(sign,&image->colormap[i].red,&image->colormap[i].green,
- &image->colormap[i].blue);
+ {
+ double
+ blue,
+ green,
+ red;
+
+ Contrast(sign,&red,&green,&blue);
+ image->colormap[i].red=(MagickRealType) red;
+ image->colormap[i].red=(MagickRealType) red;
+ image->colormap[i].red=(MagickRealType) red;
+ }
}
/*
Contrast enhance image.
{
#define EnhancePixel(weight) \
mean=((double) r[i]+GetPixelChannel(enhance_image,channel,q))/2.0; \
- distance=(double) r[i]-(double) GetPixelChannel( \
- enhance_image,channel,q); \
- distance_squared=QuantumScale*(2.0*((double) QuantumRange+1.0)+ \
- mean)*distance*distance; \
- if (distance_squared < ((double) QuantumRange*(double) \
- QuantumRange/25.0f)) \
+ distance=(double) r[i]-(double) GetPixelChannel(enhance_image,channel,q); \
+ distance_squared=QuantumScale*(2.0*((double) QuantumRange+1.0)+mean)* \
+ distance*distance; \
+ if (distance_squared < ((double) QuantumRange*(double) QuantumRange/25.0f)) \
{ \
aggregate+=(weight)*r[i]; \
total_weight+=(weight); \
Negate image.
*/
#if defined(MAGICKCORE_OPENMP_SUPPORT)
- #pragma omp parallel for schedule(static) shared(progress,status) \
+ #pragma omp parallel for schedule(static,4) shared(progress,status) \
dynamic_number_threads(image,image->columns,image->rows,1)
#endif
for (y=0; y < (ssize_t) image->rows; y++)
% 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;
+/*
+ ImageMagick 6 has a version of this function which uses LUTs.
+*/
- MagickBooleanType
- status;
+/*
+ Sigmoidal function Sigmoidal with inflexion point moved to b and "slope
+ constant" set to a.
- MagickOffsetType
- progress;
+ The first version, based on the hyperbolic tangent tanh, when combined with
+ the scaling step, is an exact arithmetic clone of the the sigmoid function
+ based on the logistic curve. The equivalence is based on the identity
- ssize_t
- y;
+ 1/(1+exp(-t)) = (1+tanh(t/2))/2
- /*
- Side effect: clamps values unless contrast<MagickEpsilon, in which
- case nothing is done.
- */
- if (contrast<MagickEpsilon)
- return(MagickTrue);
+ (http://de.wikipedia.org/wiki/Sigmoidfunktion) and the fact that the
+ scaled sigmoidal derivation is invariant under affine transformations of
+ the ordinate.
- /*
- Sigmoidal function with inflexion point moved to b and "slope
- constant" set to a.
- The first version, based on the hyperbolic tangent tanh, when
- combined with the scaling step, is an exact arithmetic clone of the
- the sigmoid function based on the logistic curve. The equivalence is
- based on the identity
- 1/(1+exp(-t)) = (1+tanh(t/2))/2
- (http://de.wikipedia.org/wiki/Sigmoidfunktion) and the fact that the
- scaled sigmoidal derivation is invariant under affine transformations
- of the ordinate.
- The tanh version is almost certainly more accurate and cheaper.
- The 0.5 factor in its argument is to clone the legacy ImageMagick
- behavior. The reason for making the define depend on atanh even
- though it only uses tanh has to do with the construction of the
- inverse of the scaled sigmoidal.
- */
+ The tanh version is almost certainly more accurate and cheaper. The 0.5
+ factor in the argument is to clone the legacy ImageMagick behavior. The
+ reason for making the define depend on atanh even though it only uses tanh
+ has to do with the construction of the inverse of the scaled sigmoidal.
+*/
#if defined(MAGICKCORE_HAVE_ATANH)
#define Sigmoidal(a,b,x) ( tanh((0.5*(a))*((x)-(b))) )
#else
#define Sigmoidal(a,b,x) ( 1.0/(1.0+exp((a)*((b)-(x)))) )
#endif
- /*
- Scaled sigmoidal formula:
+/*
+ Scaled sigmoidal function:
+
( 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 below 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 from in gamut values, hence the branching. In
+ addition, HDRI may have out of gamut values.
+ InverseScaledSigmoidal is not a two-sided inverse of ScaledSigmoidal:
+ It is only a right inverse. This is unavoidable.
+*/
+static inline double InverseScaledSigmoidal(const double a,const double b,
+ const double x)
+{
+ const double sig0=Sigmoidal(a,b,0.0);
+ const double sig1=Sigmoidal(a,b,1.0);
+ const double argument=(sig1-sig0)*x+sig0;
+ const double clamped=
+ (
#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); })
+ argument < -1+MagickEpsilon
+ ?
+ -1+MagickEpsilon
+ :
+ ( argument > 1-MagickEpsilon ? 1-MagickEpsilon : argument )
+ );
+ return(b+(2.0/a)*atanh(clamped));
#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); })
+ argument < MagickEpsilon
+ ?
+ MagickEpsilon
+ :
+ ( argument > 1-MagickEpsilon ? 1-MagickEpsilon : argument )
+ );
+ return(b-log(1.0/clamped-1.0)/a);
#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: may clamp values unless contrast<MagickEpsilon, in which
+ case nothing is done.
+ */
+ if (contrast < MagickEpsilon)
+ return(MagickTrue);
/*
Sigmoidal-contrast enhance colormap.
*/