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/contrast.c
Created Mar 9, 2017

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#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <MagickWand/MagickWand.h>
int main(int argc,char **argv)
{
#define QuantumScale ((MagickRealType) 1.0/(MagickRealType) QuantumRange)
#define SigmoidalContrast(x) \
(QuantumRange*(1.0/(1+exp(10.0*(0.5-QuantumScale*x)))-0.0066928509)*1.0092503)
#define ThrowWandException(wand) \
{ \
char \
*description; \
\
ExceptionType \
severity; \
\
description=MagickGetException(wand,&severity); \
(void) fprintf(stderr,"%s %s %lu %s\n",GetMagickModule(),description); \
description=(char *) MagickRelinquishMemory(description); \
exit(-1); \
}
MagickBooleanType
status;
PixelInfo
pixel;
MagickWand
*contrast_wand,
*image_wand;
PixelIterator
*contrast_iterator,
*iterator;
PixelWand
**contrast_pixels,
**pixels;
register ssize_t
x;
size_t
width;
ssize_t
y;
if (argc != 3)
{
(void) fprintf(stdout,"Usage: %s image sigmoidal-image\n",argv[0]);
exit(0);
}
/*
Read an image.
*/
MagickWandGenesis();
image_wand=NewMagickWand();
status=MagickReadImage(image_wand,argv[1]);
if (status == MagickFalse)
ThrowWandException(image_wand);
contrast_wand=CloneMagickWand(image_wand);
/*
Sigmoidal non-linearity contrast control.
*/
iterator=NewPixelIterator(image_wand);
contrast_iterator=NewPixelIterator(contrast_wand);
if ((iterator == (PixelIterator *) NULL) ||
(contrast_iterator == (PixelIterator *) NULL))
ThrowWandException(image_wand);
for (y=0; y < (ssize_t) MagickGetImageHeight(image_wand); y++)
{
pixels=PixelGetNextIteratorRow(iterator,&width);
contrast_pixels=PixelGetNextIteratorRow(contrast_iterator,&width);
if ((pixels == (PixelWand **) NULL) ||
(contrast_pixels == (PixelWand **) NULL))
break;
for (x=0; x < (ssize_t) width; x++)
{
PixelGetMagickColor(pixels[x],&pixel);
pixel.red=SigmoidalContrast(pixel.red);
pixel.green=SigmoidalContrast(pixel.green);
pixel.blue=SigmoidalContrast(pixel.blue);
pixel.index=SigmoidalContrast(pixel.index);
PixelSetPixelColor(contrast_pixels[x],&pixel);
}
(void) PixelSyncIterator(contrast_iterator);
}
if (y < (ssize_t) MagickGetImageHeight(image_wand))
ThrowWandException(image_wand);
contrast_iterator=DestroyPixelIterator(contrast_iterator);
iterator=DestroyPixelIterator(iterator);
image_wand=DestroyMagickWand(image_wand);
/*
Write the image then destroy it.
*/
status = MagickStripImage(contrast_wand);
if (status == MagickFalse)
ThrowWandException(image_wand);
status=MagickWriteImage(contrast_wand,argv[2]);
if (status == MagickFalse)
ThrowWandException(image_wand);
contrast_wand=DestroyMagickWand(contrast_wand);
MagickWandTerminus();
return(0);
}
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