for (i=0; i < (ssize_t) image->colors; i++)
{
/*
- Apply transfer function to colormap.
+ Apply transfer function to colormap.
*/
double
- luma;
+ luma;
luma=0.21267*image->colormap[i].red+0.71526*image->colormap[i].green+
- 0.07217*image->colormap[i].blue;
+ 0.07217*image->colormap[i].blue;
image->colormap[i].red=luma+color_correction.saturation*cdl_map[
- ScaleQuantumToMap(ClampToQuantum(image->colormap[i].red))].red-luma;
+ ScaleQuantumToMap(ClampToQuantum(image->colormap[i].red))].red-luma;
image->colormap[i].green=luma+color_correction.saturation*cdl_map[
ScaleQuantumToMap(ClampToQuantum(image->colormap[i].green))].green-luma;
image->colormap[i].blue=luma+color_correction.saturation*cdl_map[
for (i=0; i < (ssize_t) image->colors; i++)
{
/*
- Gamma-correct colormap.
+ Gamma-correct colormap.
*/
if ((GetPixelRedTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].red=(double) gamma_map[
+ image->colormap[i].red=(double) gamma_map[
ScaleQuantumToMap(ClampToQuantum(image->colormap[i].red))];
if ((GetPixelGreenTraits(image) & UpdatePixelTrait) != 0)
image->colormap[i].green=(double) gamma_map[
for (i=0; i < (ssize_t) image->colors; i++)
{
/*
- Negate colormap.
+ Negate colormap.
*/
if (grayscale != MagickFalse)
- if ((image->colormap[i].red != image->colormap[i].green) ||
- (image->colormap[i].green != image->colormap[i].blue))
- continue;
+ if ((image->colormap[i].red != image->colormap[i].green) ||
+ (image->colormap[i].green != image->colormap[i].blue))
+ continue;
if ((GetPixelRedTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].red=QuantumRange-image->colormap[i].red;
+ image->colormap[i].red=QuantumRange-image->colormap[i].red;
if ((GetPixelGreenTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].green=QuantumRange-image->colormap[i].green;
+ image->colormap[i].green=QuantumRange-image->colormap[i].green;
if ((GetPixelBlueTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].blue=QuantumRange-image->colormap[i].blue;
+ image->colormap[i].blue=QuantumRange-image->colormap[i].blue;
}
/*
Negate image.
% o exception: return any errors or warnings in this structure.
%
*/
+
+/*
+ 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.
+*/
+#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 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).
+*/
+#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 from in gamut values, 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.
+*/
+static inline double InverseScaledSigmoidal(const double a,const double b,
+ const double x)
+{
+ const double sig0=Sigmoidal(a,b,0.0);
+ const double argument=(Sigmoidal(a,b,1.0)-sig0)*x+sig0;
+ const double clamped=
+ (
+#if defined(MAGICKCORE_HAVE_ATANH)
+ argument < -1+MagickEpsilon
+ ?
+ -1+MagickEpsilon
+ :
+ ( argument > 1-MagickEpsilon ? 1-MagickEpsilon : argument )
+ );
+ return(b+(2.0/a)*atanh(clamped));
+#else
+ argument < MagickEpsilon
+ ?
+ MagickEpsilon
+ :
+ ( argument > 1-MagickEpsilon ? 1-MagickEpsilon : argument )
+ );
+ return(b+(-1.0/a)*log(1.0/clamped+-1.0));
+#endif
+}
+
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;
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
- 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.
- */
-#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:
- ( 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. This would appear to be safe because the series
- expansion of the logistic sigmoidal function around x=b is
- 1/2-a*(b-x)/4+... so that s(1)-s(0) is about a/4. (With tanh, it's a/2.)
- */
-#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:
- */
-#if defined(MAGICKCORE_HAVE_ATANH)
-#define InverseScaledSigmoidal(a,b,x) ( (b) + (2.0/(a)) * atanh( \
- (Sigmoidal((a),(b),1.0)-Sigmoidal((a),(b),0.0))*(x)+Sigmoidal((a),(b),0.0) ) )
-#else
-#define InverseScaledSigmoidal(a,b,x) ( (b) + (-1.0/(a)) * log( 1.0 / \
- ((Sigmoidal((a),(b),1.0)-Sigmoidal((a),(b),0.0))*(x)+Sigmoidal((a),(b),0.0)) \
- + -1.0 ) )
-#endif
- /*
- Convenience macros. No clamping needed at the end because of monotonicity.
+ Convenience macros.
*/
-#define ScaledSig(x) ( (Quantum) (QuantumRange*ScaledSigmoidal(contrast, \
- QuantumScale*midpoint,QuantumScale*ClampToQuantum((x)))) )
-#define InverseScaledSig(x) ( (Quantum) (QuantumRange*InverseScaledSigmoidal( \
- contrast,QuantumScale*midpoint,QuantumScale*ClampToQuantum((x)))) )
-
assert(image != (Image *) NULL);
assert(image->signature == MagickSignature);
if (image->debug != MagickFalse)
(void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
/*
- Sigmoidal-contrast enhance colormap:
+ Side effect: may clamp values unless contrast<MagickEpsilon, in which
+ case nothing is done.
+ */
+ if (contrast < MagickEpsilon)
+ return(MagickTrue);
+ /*
+ Sigmoidal-contrast enhance colormap.
*/
if (image->storage_class == PseudoClass)
{
register ssize_t
- i;
+ i;
if (sharpen != MagickFalse)
- {
- for (i=0; i < (ssize_t) image->colors; i++)
- {
- if ((GetPixelRedTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].red=ScaledSig(image->colormap[i].red);
- if ((GetPixelGreenTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].green=ScaledSig(image->colormap[i].green);
- if ((GetPixelBlueTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].blue=ScaledSig(image->colormap[i].blue);
- if ((GetPixelAlphaTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].alpha=ScaledSig(image->colormap[i].alpha);
- }
- }
+ for (i=0; i < (ssize_t) image->colors; i++)
+ {
+ if ((GetPixelRedTraits(image) & UpdatePixelTrait) != 0)
+ image->colormap[i].red=ScaledSig(image->colormap[i].red);
+ if ((GetPixelGreenTraits(image) & UpdatePixelTrait) != 0)
+ image->colormap[i].green=ScaledSig(image->colormap[i].green);
+ if ((GetPixelBlueTraits(image) & UpdatePixelTrait) != 0)
+ image->colormap[i].blue=ScaledSig(image->colormap[i].blue);
+ if ((GetPixelAlphaTraits(image) & UpdatePixelTrait) != 0)
+ image->colormap[i].alpha=ScaledSig(image->colormap[i].alpha);
+ }
else
- {
- for (i=0; i < (ssize_t) image->colors; i++)
- {
- if ((GetPixelRedTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].red=
- InverseScaledSig(image->colormap[i].red);
- if ((GetPixelGreenTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].green=
- InverseScaledSig(image->colormap[i].green);
- if ((GetPixelBlueTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].blue=
- InverseScaledSig(image->colormap[i].blue);
- if ((GetPixelAlphaTraits(image) & UpdatePixelTrait) != 0)
- image->colormap[i].alpha=
- InverseScaledSig(image->colormap[i].alpha);
- }
- }
+ for (i=0; i < (ssize_t) image->colors; i++)
+ {
+ if ((GetPixelRedTraits(image) & UpdatePixelTrait) != 0)
+ image->colormap[i].red=InverseScaledSig(image->colormap[i].red);
+ if ((GetPixelGreenTraits(image) & UpdatePixelTrait) != 0)
+ image->colormap[i].green=InverseScaledSig(image->colormap[i].green);
+ if ((GetPixelBlueTraits(image) & UpdatePixelTrait) != 0)
+ image->colormap[i].blue=InverseScaledSig(image->colormap[i].blue);
+ if ((GetPixelAlphaTraits(image) & UpdatePixelTrait) != 0)
+ image->colormap[i].alpha=InverseScaledSig(image->colormap[i].alpha);
+ }
}
/*
- Sigmoidal-contrast enhance image:
+ Sigmoidal-contrast enhance image.
*/
status=MagickTrue;
progress=0;
for (x=0; x < (ssize_t) image->columns; x++)
{
register ssize_t
- i;
+ i;
if (GetPixelMask(image,q) != 0)
{
traits=GetPixelChannelTraits(image,channel);
if ((traits & UpdatePixelTrait) == 0)
continue;
- if (sharpen != MagickFalse)
- q[i]=ScaledSig(q[i]);
- else
- q[i]=InverseScaledSig(q[i]);
+ if (sharpen != MagickFalse)
+ q[i]=ScaledSig(q[i]);
+ else
+ q[i]=InverseScaledSig(q[i]);
}
q+=GetPixelChannels(image);
}
projects / imagemagick / blobdiff