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DEFINITIONS
This source file includes following definitions.
- ReadSTEGANOImage
- RegisterSTEGANOImage
- UnregisterSTEGANOImage
/*
% Copyright (C) 2003 GraphicsMagick Group
% Copyright (C) 2002 ImageMagick Studio
% Copyright 1991-1999 E. I. du Pont de Nemours and Company
%
% This program is covered by multiple licenses, which are described in
% Copyright.txt. You should have received a copy of Copyright.txt with this
% package; otherwise see http://www.graphicsmagick.org/www/Copyright.html.
%
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% SSSSS TTTTT EEEEE GGGG AAA N N OOO %
% SS T E G A A NN N O O %
% SSS T EEE G GG AAAAA N N N O O %
% SS T E G G A A N NN O O %
% SSSSS T EEEEE GGG A A N N OOO %
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% Write A Steganographic Image. %
% %
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% Software Design %
% John Cristy %
% July 1992 %
% %
% %
% %
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%
%
*/
/*
Include declarations.
*/
#include "magick/studio.h"
#include "magick/blob.h"
#include "magick/colormap.h"
#include "magick/constitute.h"
#include "magick/magick.h"
#include "magick/monitor.h"
#include "magick/pixel_cache.h"
#include "magick/utility.h"
/*
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% R e a d S T E G A N O I m a g e %
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% Method ReadSTEGANOImage reads a steganographic image hidden within another
% image type. It allocates the memory necessary for the new Image structure
% and returns a pointer to the new image.
%
% The format of the ReadSTEGANOImage method is:
%
% Image *ReadSTEGANOImage(const ImageInfo *image_info,
% ExceptionInfo *exception)
%
% A description of each parameter follows:
%
% o image: Method ReadSTEGANOImage returns a pointer to the image
% after reading. A null image is returned if there is a memory shortage
% of if the image cannot be read.
%
% o image_info: Specifies a pointer to a ImageInfo structure.
%
% o exception: return any errors or warnings in this structure.
%
%
*/
static Image *ReadSTEGANOImage(const ImageInfo *image_info,
ExceptionInfo *exception)
{
#define GetBit(a,i) (((a) >> (i)) & 0x01)
#define SetBit(a,i,set) \
a=(Quantum) ((set) ? (a) | (1UL << (i)) : (a) & ~(1UL << (i)))
Image
*image,
*watermark;
ImageInfo
*clone_info;
unsigned long
y;
long
k;
int
c,
i,
j;
PixelPacket
pixel;
register IndexPacket
*indexes;
register unsigned long
x;
register PixelPacket
*q;
/*
Initialize Image structure.
*/
assert(image_info != (const ImageInfo *) NULL);
assert(image_info->signature == MagickSignature);
assert(exception != (ExceptionInfo *) NULL);
assert(exception->signature == MagickSignature);
image=AllocateImage(image_info);
if ((image->columns == 0) || (image->rows == 0))
ThrowReaderException(OptionError,MustSpecifyImageSize,image);
clone_info=CloneImageInfo(image_info);
clone_info->blob=(void *) NULL;
clone_info->length=0;
*clone_info->magick='\0';
watermark=ReadImage(clone_info,exception);
DestroyImageInfo(clone_info);
if (watermark == (Image *) NULL)
return((Image *) NULL);
watermark->depth=QuantumDepth;
if (!AllocateImageColormap(image,MaxColormapSize))
ThrowReaderException(ResourceLimitError,MemoryAllocationFailed,image);
if (image_info->ping)
{
CloseBlob(image);
return(image);
}
/*
Get hidden watermark from low-order bits of image.
*/
c=0;
i=0;
j=0;
k=image->offset;
for (i=QuantumDepth-1; (i >= 0) && (j < QuantumDepth); i--)
{
for (y=0; (y < image->rows) && (j < QuantumDepth); y++)
{
for (x=0; (x < image->columns) && (j < QuantumDepth); x++)
{
(void) AcquireOnePixelByReference(watermark,&pixel,k % watermark->columns,
k/watermark->columns,exception);
q=GetImagePixels(image,x,y,1,1);
if (q == (PixelPacket *) NULL)
break;
indexes=AccessMutableIndexes(image);
switch (c)
{
case 0:
{
SetBit(*indexes,i,GetBit(pixel.red,j));
break;
}
case 1:
{
SetBit(*indexes,i,GetBit(pixel.green,j));
break;
}
case 2:
{
SetBit(*indexes,i,GetBit(pixel.blue,j));
break;
}
}
(void) SyncImage(image);
c++;
if (c == 3)
c=0;
k++;
if ((unsigned long) k == watermark->columns*watermark->columns)
k=0;
if (k == image->offset)
j++;
}
}
if (!MagickMonitorFormatted(i,QuantumDepth,&image->exception,
LoadImagesText,image->filename))
break;
}
DestroyImage(watermark);
(void) SyncImage(image);
return(image);
}
/*
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% R e g i s t e r S T E G A N O I m a g e %
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% Method RegisterSTEGANOImage adds attributes for the STEGANO image format to
% the list of supported formats. The attributes include the image format
% tag, a method to read and/or write the format, whether the format
% supports the saving of more than one frame to the same file or blob,
% whether the format supports native in-memory I/O, and a brief
% description of the format.
%
% The format of the RegisterSTEGANOImage method is:
%
% RegisterSTEGANOImage(void)
%
*/
ModuleExport void RegisterSTEGANOImage(void)
{
MagickInfo
*entry;
entry=SetMagickInfo("STEGANO");
entry->decoder=(DecoderHandler) ReadSTEGANOImage;
entry->description="Steganographic image";
entry->module="STEGANO";
entry->coder_class=PrimaryCoderClass;
entry->extension_treatment=IgnoreExtensionTreatment;
(void) RegisterMagickInfo(entry);
}
/*
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% U n r e g i s t e r S T E G A N O I m a g e %
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%
% Method UnregisterSTEGANOImage removes format registrations made by the
% STEGANO module from the list of supported formats.
%
% The format of the UnregisterSTEGANOImage method is:
%
% UnregisterSTEGANOImage(void)
%
*/
ModuleExport void UnregisterSTEGANOImage(void)
{
(void) UnregisterMagickInfo("STEGANO");
}