root / ImageMagick / trunk / magick / compare.c

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%               CCCC   OOO   M   M  PPPP    AAA   RRRR    EEEEE               %
%              C      O   O  MM MM  P   P  A   A  R   R   E                   %
%              C      O   O  M M M  PPPP   AAAAA  RRRR    EEE                 %
%              C      O   O  M   M  P      A   A  R R     E                   %
%               CCCC   OOO   M   M  P      A   A  R  R    EEEEE               %
%                                                                             %
%                                                                             %
%                         Image Comparison Methods                            %
%                                                                             %
%                              Software Design                                %
%                                John Cristy                                  %
%                               December 2003                                 %
%                                                                             %
%                                                                             %
%  Copyright 1999-2008 ImageMagick Studio LLC, a non-profit organization      %
%  dedicated to making software imaging solutions freely available.           %
%                                                                             %
%  You may not use this file except in compliance with the License.  You may  %
%  obtain a copy of the License at                                            %
%                                                                             %
%    http://www.imagemagick.org/script/license.php                            %
%                                                                             %
%  Unless required by applicable law or agreed to in writing, software        %
%  distributed under the License is distributed on an "AS IS" BASIS,          %
%  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.   %
%  See the License for the specific language governing permissions and        %
%  limitations under the License.                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%
%
*/

/*
  Include declarations.
*/
#include "magick/studio.h"
#include "magick/artifact.h"
#include "magick/cache-view.h"
#include "magick/client.h"
#include "magick/color.h"
#include "magick/color-private.h"
#include "magick/colorspace.h"
#include "magick/colorspace-private.h"
#include "magick/compare.h"
#include "magick/composite-private.h"
#include "magick/constitute.h"
#include "magick/exception-private.h"
#include "magick/geometry.h"
#include "magick/image-private.h"
#include "magick/list.h"
#include "magick/log.h"
#include "magick/memory_.h"
#include "magick/option.h"
#include "magick/pixel-private.h"
#include "magick/resource_.h"
#include "magick/string_.h"
#include "magick/utility.h"
#include "magick/version.h"

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   C o m p a r e I m a g e C h a n n e l s                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  CompareImageChannels() compares one or more image channels of an image
%  to a reconstructed image and returns the difference image.
%
%  The format of the CompareImageChannels method is:
%
%      Image *CompareImageChannels(const Image *image,
%        const Image *reconstruct_image,const ChannelType channel,
%        const MetricType metric,double *distortion,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o reconstruct_image: the reconstruct image.
%
%    o channel: the channel.
%
%    o metric: the metric.
%
%    o distortion: the computed distortion between the images.
%
%    o exception: Return any errors or warnings in this structure.
%
*/

MagickExport Image *CompareImages(Image *image,const Image *reconstruct_image,
  const MetricType metric,double *distortion,ExceptionInfo *exception)
{
  Image
    *highlight_image;

  highlight_image=CompareImageChannels(image,reconstruct_image,AllChannels,
    metric,distortion,exception);
  return(highlight_image);
}

MagickExport Image *CompareImageChannels(Image *image,
  const Image *reconstruct_image,const ChannelType channel,
  const MetricType metric,double *distortion,ExceptionInfo *exception)
{
  const char
    *artifact;

  Image
    *difference_image,
    *highlight_image;

  long
    y;

  MagickBooleanType
    status;

  MagickPixelPacket
    highlight,
    lowlight;

  ViewInfo
    **highlight_view,
    **image_view,
    **reconstruct_view;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(reconstruct_image != (const Image *) NULL);
  assert(reconstruct_image->signature == MagickSignature);
  assert(distortion != (double *) NULL);
  *distortion=0.0;
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if ((reconstruct_image->columns != image->columns) ||
      (reconstruct_image->rows != image->rows))
    ThrowImageException(ImageError,"ImageSizeDiffers");
  status=GetImageChannelDistortion(image,reconstruct_image,channel,metric,
    distortion,exception);
  if (status == MagickFalse)
    return((Image *) NULL);
  difference_image=CloneImage(image,0,0,MagickTrue,exception);
  if (difference_image == (Image *) NULL)
    return((Image *) NULL);
  (void) SetImageAlphaChannel(difference_image,ResetAlphaChannel);
  highlight_image=CloneImage(image,image->columns,image->rows,MagickTrue,
    exception);
  if (highlight_image == (Image *) NULL)
    {
      difference_image=DestroyImage(difference_image);
      return((Image *) NULL);
    }
  if (SetImageStorageClass(highlight_image,DirectClass) == MagickFalse)
    {
      InheritException(exception,&highlight_image->exception);
      difference_image=DestroyImage(difference_image);
      highlight_image=DestroyImage(highlight_image);
      return((Image *) NULL);
    }
  (void) SetImageAlphaChannel(highlight_image,ResetAlphaChannel);
  (void) QueryMagickColor("#f1001ecc",&highlight,exception);
  artifact=GetImageArtifact(image,"highlight-color");
  if (artifact != (const char *) NULL)
    (void) QueryMagickColor(artifact,&highlight,exception);
  (void) QueryMagickColor("#ffffffcc",&lowlight,exception);
  artifact=GetImageArtifact(image,"lowlight-color");
  if (artifact != (const char *) NULL)
    (void) QueryMagickColor(artifact,&lowlight,exception);
  if (highlight_image->colorspace == CMYKColorspace)
    {
      ConvertRGBToCMYK(&highlight);
      ConvertRGBToCMYK(&lowlight);
    }
  /*
    Generate difference image.
  */
  status=MagickTrue;
  image_view=AcquireCacheViewThreadSet(image);
  reconstruct_view=AcquireCacheViewThreadSet(reconstruct_image);
  highlight_view=AcquireCacheViewThreadSet(highlight_image);
  #pragma omp parallel for
  for (y=0; y < (long) image->rows; y++)
  {
    MagickPixelPacket
      pixel,
      reconstruct_pixel;

    register const IndexPacket
      *indexes,
      *reconstruct_indexes;

    register const PixelPacket
      *p,
      *q;

    register IndexPacket
      *highlight_indexes;

    register long
      id,
      x;

    register PixelPacket
      *r;

    if (status == MagickFalse)
      continue;
    id=GetCacheViewThreadId();
    p=AcquireCacheViewPixels(image_view[id],0,y,image->columns,1,exception);
    q=AcquireCacheViewPixels(reconstruct_view[id],0,y,
      reconstruct_image->columns,1,exception);
    r=SetCacheViewPixels(highlight_view[id],0,y,highlight_image->columns,1);
    if ((p == (const PixelPacket *) NULL) ||
        (q == (const PixelPacket *) NULL) || (r == (PixelPacket *) NULL))
      {
        status=MagickFalse;
        continue;
      }
    indexes=AcquireCacheViewIndexes(image_view[id]);
    reconstruct_indexes=AcquireCacheViewIndexes(reconstruct_view[id]);
    highlight_indexes=GetCacheViewIndexes(highlight_view[id]);
    GetMagickPixelPacket(image,&pixel);
    GetMagickPixelPacket(reconstruct_image,&reconstruct_pixel);
    for (x=0; x < (long) image->columns; x++)
    {
      MagickStatusType
        difference;

      SetMagickPixelPacket(image,p,indexes+x,&pixel);
      SetMagickPixelPacket(reconstruct_image,q,reconstruct_indexes+x,
        &reconstruct_pixel);
      difference=MagickFalse;
      if (channel == AllChannels)
        {
          if (IsMagickColorSimilar(&pixel,&reconstruct_pixel) == MagickFalse)
            difference=MagickTrue;
        }
      else
        {
          if (((channel & RedChannel) != 0) && (p->red != q->red))
            difference=MagickTrue;
          if (((channel & GreenChannel) != 0) && (p->green != q->green))
            difference=MagickTrue;
          if (((channel & BlueChannel) != 0) && (p->blue != q->blue))
            difference=MagickTrue;
          if (((channel & OpacityChannel) != 0) && (p->opacity != q->opacity))
            difference=MagickTrue;
          if ((((channel & IndexChannel) != 0) &&
               (image->colorspace == CMYKColorspace) &&
               (reconstruct_image->colorspace == CMYKColorspace)) &&
              (indexes[x] != reconstruct_indexes[x]))
            difference=MagickTrue;
        }
      if (difference != MagickFalse)
        SetPixelPacket(highlight_image,&highlight,r,highlight_indexes+x);
      else
        SetPixelPacket(highlight_image,&lowlight,r,highlight_indexes+x);
      p++;
      q++;
      r++;
    }
    if (SyncCacheView(highlight_view[id]) == MagickFalse)
      status=MagickFalse;
  }
  highlight_view=DestroyCacheViewThreadSet(highlight_view);
  reconstruct_view=DestroyCacheViewThreadSet(reconstruct_view);
  image_view=DestroyCacheViewThreadSet(image_view);
  (void) CompositeImage(difference_image,image->compose,highlight_image,0,0);
  highlight_image=DestroyImage(highlight_image);
  if (status == MagickFalse)
    difference_image=DestroyImage(difference_image);
  return(difference_image);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t I m a g e C h a n n e l D i s t o r t i o n                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetImageChannelDistortion() compares one or more image channels of an image
%  to a reconstructed image and returns the specified distortion metric.
%
%  The format of the CompareImageChannels method is:
%
%      MagickBooleanType GetImageChannelDistortion(const Image *image,
%        const Image *reconstruct_image,const ChannelType channel,
%        const MetricType metric,double *distortion,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o reconstruct_image: the reconstruct image.
%
%    o channel: the channel.
%
%    o metric: the metric.
%
%    o distortion: the computed distortion between the images.
%
%    o exception: Return any errors or warnings in this structure.
%
*/

MagickExport MagickBooleanType GetImageDistortion(Image *image,
  const Image *reconstruct_image,const MetricType metric,double *distortion,
  ExceptionInfo *exception)
{
  MagickBooleanType
    status;

  status=GetImageChannelDistortion(image,reconstruct_image,AllChannels,
    metric,distortion,exception);
  return(status);
}

static MagickBooleanType GetAbsoluteError(const Image *image,
  const Image *reconstruct_image,const ChannelType channel,double *distortion,
  ExceptionInfo *exception)
{
  long
    y;

  MagickBooleanType
    status;

  ViewInfo
    **image_view,
    **reconstruct_view;

  /*
    Compute the absolute difference in pixels between two images.
  */
  status=MagickTrue;
  image_view=AcquireCacheViewThreadSet(image);
  reconstruct_view=AcquireCacheViewThreadSet(reconstruct_image);
  #pragma omp parallel
  for (y=0; y < (long) image->rows; y++)
  {
    MagickPixelPacket
      pixel,
      reconstruct_pixel;

    register const IndexPacket
      *indexes,
      *reconstruct_indexes;

    register const PixelPacket
      *p,
      *q;

    register long
      id,
      x;

    if (status == MagickFalse)
      continue;
    id=GetCacheViewThreadId();
    p=AcquireCacheViewPixels(image_view[id],0,y,image->columns,1,exception);
    q=AcquireCacheViewPixels(reconstruct_view[id],0,y,
      reconstruct_image->columns,1,exception);
    if ((p == (const PixelPacket *) NULL) || (q == (const PixelPacket *) NULL))
      {
        status=MagickFalse;
        continue;
      }
    indexes=AcquireCacheViewIndexes(image_view[id]);
    reconstruct_indexes=AcquireCacheViewIndexes(reconstruct_view[id]);
    GetMagickPixelPacket(image,&pixel);
    GetMagickPixelPacket(reconstruct_image,&reconstruct_pixel);
    for (x=0; x < (long) image->columns; x++)
    {
      SetMagickPixelPacket(image,p,indexes+x,&pixel);
      SetMagickPixelPacket(reconstruct_image,q,reconstruct_indexes+x,
        &reconstruct_pixel);
      if (IsMagickColorSimilar(&pixel,&reconstruct_pixel) == MagickFalse)
        {
          if ((channel & RedChannel) != 0)
            distortion[RedChannel]++;
          if ((channel & GreenChannel) != 0)
            distortion[GreenChannel]++;
          if ((channel & BlueChannel) != 0)
            distortion[BlueChannel]++;
          if ((channel & OpacityChannel) != 0)
            distortion[OpacityChannel]++;
          if (((channel & IndexChannel) != 0) &&
              (image->colorspace == CMYKColorspace))
            distortion[BlackChannel]++;
          distortion[AllChannels]++;
        }
      p++;
      q++;
    }
  }
  reconstruct_view=DestroyCacheViewThreadSet(reconstruct_view);
  image_view=DestroyCacheViewThreadSet(image_view);
  return(status);
}

static unsigned long GetNumberChannels(const Image *image,
  const ChannelType channel)
{
  unsigned long
    channels;

  channels=0;
  if ((channel & RedChannel) != 0)
    channels++;
  if ((channel & GreenChannel) != 0)
    channels++;
  if ((channel & BlueChannel) != 0)
    channels++;
  if ((channel & OpacityChannel) != 0)
    channels++;
  if (((channel & IndexChannel) != 0) &&
      (image->colorspace == CMYKColorspace))
    channels++;
  return(channels);
}

static MagickBooleanType GetMeanAbsoluteError(const Image *image,
  const Image *reconstruct_image,const ChannelType channel,
  double *distortion,ExceptionInfo *exception)
{
  double
    scale;

  long
    y;

  MagickBooleanType
    status;

  ViewInfo
    *image_view,
    *reconstruct_view;

  status=MagickTrue;
  scale=1.0/((double) image->columns*image->rows);
  image_view=AcquireCacheView(image);
  reconstruct_view=AcquireCacheView(reconstruct_image);
  for (y=0; y < (long) image->rows; y++)
  {
    register const IndexPacket
      *indexes,
      *reconstruct_indexes;

    register const PixelPacket
      *p,
      *q;

    register long
      x;

    p=AcquireCacheViewPixels(image_view,0,y,image->columns,1,exception);
    q=AcquireCacheViewPixels(reconstruct_view,0,y,reconstruct_image->columns,1,
      exception);
    if ((p == (const PixelPacket *) NULL) || (q == (const PixelPacket *) NULL))
      {
        status=MagickFalse;
        break;
      }
    indexes=AcquireCacheViewIndexes(image_view);
    reconstruct_indexes=AcquireCacheViewIndexes(reconstruct_view);
    for (x=0; x < (long) image->columns; x++)
    {
      MagickRealType
        distance;

      if ((channel & RedChannel) != 0)
        {
          distance=fabs(p->red-(double) q->red);
          distortion[RedChannel]+=scale*distance;
          distortion[AllChannels]+=scale*distance;
        }
      if ((channel & GreenChannel) != 0)
        {
          distance=fabs(p->green-(double) q->green);
          distortion[GreenChannel]+=scale*distance;
          distortion[AllChannels]+=scale*distance;
        }
      if ((channel & BlueChannel) != 0)
        {
          distance=fabs(p->blue-(double) q->blue);
          distortion[BlueChannel]+=scale*distance;
          distortion[AllChannels]+=scale*distance;
        }
      if ((channel & OpacityChannel) != 0)
        {
          distance=fabs(p->opacity-(double) q->opacity);
          distortion[OpacityChannel]+=scale*distance;
          distortion[AllChannels]+=scale*distance;
        }
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace))
        {
          distance=fabs(indexes[x]-(double) reconstruct_indexes[x]);
          distortion[BlackChannel]+=scale*distance;
          distortion[AllChannels]+=scale*distance;
        }
      p++;
      q++;
    }
  }
  reconstruct_view=DestroyCacheView(reconstruct_view);
  image_view=DestroyCacheView(image_view);
  distortion[AllChannels]/=(double) GetNumberChannels(image,channel);
  return(status);
}

static MagickBooleanType GetMeanErrorPerPixel(Image *image,
  const Image *reconstruct_image,const ChannelType channel,double *distortion,
  ExceptionInfo *exception)
{
  long
    y;

  MagickBooleanType
    status;

  MagickRealType
    alpha,
    area,
    beta,
    maximum_error,
    mean_error;

  ViewInfo
    *image_view,
    *reconstruct_view;

  status=MagickTrue;
  alpha=1.0;
  beta=1.0;
  area=0.0;
  maximum_error=0.0;
  mean_error=0.0;
  image_view=AcquireCacheView(image);
  reconstruct_view=AcquireCacheView(reconstruct_image);
  for (y=0; y < (long) image->rows; y++)
  {
    register const IndexPacket
      *indexes,
      *reconstruct_indexes;

    register const PixelPacket
      *p,
      *q;

    register long
      x;

    p=AcquireCacheViewPixels(image_view,0,y,image->columns,1,exception);
    q=AcquireCacheViewPixels(reconstruct_view,0,y,reconstruct_image->columns,1,
      exception);
    if ((p == (const PixelPacket *) NULL) || (q == (const PixelPacket *) NULL))
      {
        status=MagickFalse;
        break;
      }
    indexes=AcquireCacheViewIndexes(image_view);
    reconstruct_indexes=AcquireCacheViewIndexes(reconstruct_view);
    for (x=0; x < (long) image->columns; x++)
    {
      MagickRealType
        distance;

      if ((channel & OpacityChannel) != 0)
        {
          if (image->matte != MagickFalse)
            alpha=(MagickRealType) (QuantumScale*(QuantumRange-p->opacity));
          if (reconstruct_image->matte != MagickFalse)
            beta=(MagickRealType) (QuantumScale*(QuantumRange-q->opacity));
        }
      if ((channel & RedChannel) != 0)
        {
          distance=fabs(alpha*p->red-beta*q->red);
          distortion[RedChannel]+=distance;
          distortion[AllChannels]+=distance;
          mean_error+=distance*distance;
          if (distance > maximum_error)
            maximum_error=distance;
          area++;
        }
      if ((channel & GreenChannel) != 0)
        {
          distance=fabs(alpha*p->green-beta*q->green);
          distortion[GreenChannel]+=distance;
          distortion[AllChannels]+=distance;
          mean_error+=distance*distance;
          if (distance > maximum_error)
            maximum_error=distance;
          area++;
        }
      if ((channel & BlueChannel) != 0)
        {
          distance=fabs(alpha*p->blue-beta*q->blue);
          distortion[BlueChannel]+=distance;
          distortion[AllChannels]+=distance;
          mean_error+=distance*distance;
          if (distance > maximum_error)
            maximum_error=distance;
          area++;
        }
      if ((channel & OpacityChannel) != 0)
        {
          distance=fabs(alpha*p->opacity-beta*q->opacity);
          distortion[OpacityChannel]+=distance;
          distortion[AllChannels]+=distance;
          mean_error+=distance*distance;
          if (distance > maximum_error)
            maximum_error=distance;
          area++;
        }
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace) &&
          (reconstruct_image->colorspace == CMYKColorspace))
        {
          distance=fabs(alpha*indexes[x]-beta*reconstruct_indexes[x]);
          distortion[BlackChannel]+=distance;
          distortion[AllChannels]+=distance;
          mean_error+=distance*distance;
          if (distance > maximum_error)
            maximum_error=distance;
          area++;
        }
      p++;
      q++;
    }
  }
  reconstruct_view=DestroyCacheView(reconstruct_view);
  image_view=DestroyCacheView(image_view);
  image->error.mean_error_per_pixel=distortion[AllChannels]/area;
  image->error.normalized_mean_error=QuantumScale*QuantumScale*mean_error/area;
  image->error.normalized_maximum_error=QuantumScale*maximum_error;
  return(status);
}

static MagickBooleanType GetMeanSquaredError(const Image *image,
  const Image *reconstruct_image,const ChannelType channel,
  double *distortion,ExceptionInfo *exception)
{
  double
    scale;

  long
    y;

  MagickBooleanType
    status;

  ViewInfo
    *image_view,
    *reconstruct_view;

  status=MagickTrue;
  scale=1.0/((double) image->columns*image->rows);
  image_view=AcquireCacheView(image);
  reconstruct_view=AcquireCacheView(reconstruct_image);
  for (y=0; y < (long) image->rows; y++)
  {
    register const IndexPacket
      *indexes,
      *reconstruct_indexes;

    register const PixelPacket
      *p,
      *q;

    register long
      x;

    p=AcquireCacheViewPixels(image_view,0,y,image->columns,1,exception);
    q=AcquireCacheViewPixels(reconstruct_view,0,y,reconstruct_image->columns,1,
      exception);
    if ((p == (const PixelPacket *) NULL) || (q == (const PixelPacket *) NULL))
      {
        status=MagickFalse;
        break;
      }
    indexes=AcquireCacheViewIndexes(image_view);
    reconstruct_indexes=AcquireCacheViewIndexes(reconstruct_view);
    for (x=0; x < (long) image->columns; x++)
    {
      MagickRealType
        distance;

      if ((channel & RedChannel) != 0)
        {
          distance=(p->red-(MagickRealType) q->red);
          distortion[RedChannel]+=QuantumScale*scale*distance*distance;
          distortion[AllChannels]+=QuantumScale*scale*distance*distance;
        }
      if ((channel & GreenChannel) != 0)
        {
          distance=(p->green-(MagickRealType) q->green);
          distortion[GreenChannel]+=QuantumScale*scale*distance*distance;
          distortion[AllChannels]+=QuantumScale*scale*distance*distance;
        }
      if ((channel & BlueChannel) != 0)
        {
          distance=(p->blue-(MagickRealType) q->blue);
          distortion[BlueChannel]+=QuantumScale*scale*distance*distance;
          distortion[AllChannels]+=QuantumScale*scale*distance*distance;
        }
      if ((channel & OpacityChannel) != 0)
        {
          distance=(p->opacity-(MagickRealType) q->opacity);
          distortion[OpacityChannel]+=QuantumScale*scale*distance*distance;
          distortion[AllChannels]+=QuantumScale*scale*distance*distance;
        }
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace) &&
          (reconstruct_image->colorspace == CMYKColorspace))
        {
          distance=(indexes[x]-(MagickRealType) reconstruct_indexes[x]);
          distortion[BlackChannel]+=QuantumScale*scale*distance*distance;
          distortion[AllChannels]+=QuantumScale*scale*distance*distance;
        }
      p++;
      q++;
    }
  }
  reconstruct_view=DestroyCacheView(reconstruct_view);
  image_view=DestroyCacheView(image_view);
  distortion[AllChannels]/=(double) GetNumberChannels(image,channel);
  return(status);
}

static MagickBooleanType GetPeakAbsoluteError(const Image *image,
  const Image *reconstruct_image,const ChannelType channel,
  double *distortion,ExceptionInfo *exception)
{
  long
    y;

  MagickBooleanType
    status;

  ViewInfo
    *image_view,
    *reconstruct_view;

  status=MagickTrue;
  image_view=AcquireCacheView(image);
  reconstruct_view=AcquireCacheView(reconstruct_image);
  for (y=0; y < (long) image->rows; y++)
  {
    register const IndexPacket
      *indexes,
      *reconstruct_indexes;

    register const PixelPacket
      *p,
      *q;

    register long
      x;

    p=AcquireCacheViewPixels(image_view,0,y,image->columns,1,exception);
    q=AcquireCacheViewPixels(reconstruct_view,0,y,reconstruct_image->columns,1,
      exception);
    if ((p == (const PixelPacket *) NULL) || (q == (const PixelPacket *) NULL))
      break;
    indexes=AcquireCacheViewIndexes(image_view);
    reconstruct_indexes=AcquireCacheViewIndexes(reconstruct_view);
    for (x=0; x < (long) image->columns; x++)
    {
      MagickRealType
        distance;

      if ((channel & RedChannel) != 0)
        {
          distance=fabs(p->red-(double) q->red);
          if (distance > distortion[RedChannel])
            distortion[RedChannel]=distance;
          if (distance > distortion[AllChannels])
            distortion[AllChannels]=distance;
        }
      if ((channel & GreenChannel) != 0)
        {
          distance=fabs(p->green-(double) q->green);
          if (distance > distortion[GreenChannel])
            distortion[GreenChannel]=distance;
          if (distance > distortion[AllChannels])
            distortion[AllChannels]=distance;
        }
      if ((channel & BlueChannel) != 0)
        {
          distance=fabs(p->blue-(double) q->blue);
          if (distance > distortion[BlueChannel])
            distortion[BlueChannel]=distance;
          if (distance > distortion[AllChannels])
            distortion[AllChannels]=distance;
        }
      if ((channel & OpacityChannel) != 0)
        {
          distance=fabs(p->opacity-(double) q->opacity);
          if (distance > distortion[OpacityChannel])
            distortion[OpacityChannel]=distance;
          if (distance > distortion[AllChannels])
            distortion[AllChannels]=distance;
        }
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace) &&
          (reconstruct_image->colorspace == CMYKColorspace))
        {
          distance=fabs(indexes[x]-(double) reconstruct_indexes[x]);
          if (distance > distortion[BlackChannel])
            distortion[BlackChannel]=distance;
          if (distance > distortion[AllChannels])
            distortion[AllChannels]=distance;
        }
      p++;
      q++;
    }
  }
  reconstruct_view=DestroyCacheView(reconstruct_view);
  image_view=DestroyCacheView(image_view);
  return(status);
}

static MagickBooleanType GetPeakSignalToNoiseRatio(const Image *image,
  const Image *reconstruct_image,const ChannelType channel,
  double *distortion,ExceptionInfo *exception)
{
  MagickBooleanType
    status;

  status=GetMeanSquaredError(image,reconstruct_image,channel,distortion,
    exception);
  if ((channel & RedChannel) != 0)
    distortion[RedChannel]=20.0*log10((double) QuantumRange/
      sqrt(distortion[RedChannel]));
  if ((channel & GreenChannel) != 0)
    distortion[GreenChannel]=20.0*log10((double) QuantumRange/
      sqrt(distortion[GreenChannel]));
  if ((channel & BlueChannel) != 0)
    distortion[BlueChannel]=20.0*log10((double) QuantumRange/
      sqrt(distortion[BlueChannel]));
  if ((channel & OpacityChannel) != 0)
    distortion[OpacityChannel]=20.0*log10((double) QuantumRange/
      sqrt(distortion[OpacityChannel]));
  if (((channel & IndexChannel) != 0) &&
      (image->colorspace == CMYKColorspace))
    distortion[BlackChannel]=20.0*log10((double) QuantumRange/
      sqrt(distortion[BlackChannel]));
  distortion[AllChannels]=20.0*log10((double) QuantumRange/
    sqrt((double) distortion[AllChannels]));
  return(status);
}

static MagickBooleanType GetRootMeanSquaredError(const Image *image,
  const Image *reconstruct_image,const ChannelType channel,
  double *distortion,ExceptionInfo *exception)
{
  MagickBooleanType
    status;

  status=GetMeanSquaredError(image,reconstruct_image,channel,distortion,
    exception);
  if ((channel & RedChannel) != 0)
    distortion[RedChannel]=sqrt(distortion[RedChannel]);
  if ((channel & GreenChannel) != 0)
    distortion[GreenChannel]=sqrt(distortion[GreenChannel]);
  if ((channel & BlueChannel) != 0)
    distortion[BlueChannel]=sqrt(distortion[BlueChannel]);
  if ((channel & OpacityChannel) != 0)
    distortion[OpacityChannel]=sqrt(distortion[OpacityChannel]);
  if (((channel & IndexChannel) != 0) &&
      (image->colorspace == CMYKColorspace))
    distortion[BlackChannel]=sqrt(distortion[BlackChannel]);
  distortion[AllChannels]=sqrt(distortion[AllChannels]);
  return(status);
}

MagickExport MagickBooleanType GetImageChannelDistortion(Image *image,
  const Image *reconstruct_image,const ChannelType channel,
  const MetricType metric,double *distortion,ExceptionInfo *exception)
{
  double
    *channel_distortion;

  MagickBooleanType
    status;

  size_t
    length;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(reconstruct_image != (const Image *) NULL);
  assert(reconstruct_image->signature == MagickSignature);
  assert(distortion != (double *) NULL);
  *distortion=0.0;
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if ((reconstruct_image->columns != image->columns) ||
      (reconstruct_image->rows != image->rows))
    ThrowBinaryException(ImageError,"ImageSizeDiffers",image->filename);
  /*
    Get image distortion.
  */
  length=AllChannels+1UL;
  channel_distortion=(double *) AcquireQuantumMemory(length,
    sizeof(*channel_distortion));
  if (channel_distortion == (double *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
  (void) ResetMagickMemory(channel_distortion,0,length*
    sizeof(*channel_distortion));
  switch (metric)
  {
    case AbsoluteErrorMetric:
    {
      status=GetAbsoluteError(image,reconstruct_image,channel,
        channel_distortion,exception);
      break;
    }
    case MeanAbsoluteErrorMetric:
    {
      status=GetMeanAbsoluteError(image,reconstruct_image,channel,
        channel_distortion,exception);
      break;
    }
    case MeanErrorPerPixelMetric:
    {
      status=GetMeanErrorPerPixel(image,reconstruct_image,channel,
        channel_distortion,exception);
      break;
    }
    case MeanSquaredErrorMetric:
    {
      status=GetMeanSquaredError(image,reconstruct_image,channel,
        channel_distortion,exception);
      break;
    }
    case PeakAbsoluteErrorMetric:
    default:
    {
      status=GetPeakAbsoluteError(image,reconstruct_image,channel,
        channel_distortion,exception);
      break;
    }
    case PeakSignalToNoiseRatioMetric:
    {
      status=GetPeakSignalToNoiseRatio(image,reconstruct_image,channel,
        channel_distortion,exception);
      break;
    }
    case RootMeanSquaredErrorMetric:
    {
      status=GetRootMeanSquaredError(image,reconstruct_image,channel,
        channel_distortion,exception);
      break;
    }
  }
  *distortion=channel_distortion[AllChannels];
  channel_distortion=(double *) RelinquishMagickMemory(channel_distortion);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t I m a g e C h a n n e l D i s t o r t i o n s                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetImageChannelDistrortion() compares the image channels of an image to a
%  reconstructed image and returns the specified distortion metric for each
%  channel.
%
%  The format of the CompareImageChannels method is:
%
%      double *GetImageChannelDistortions(const Image *image,
%        const Image *reconstruct_image,const MetricType metric,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o reconstruct_image: the reconstruct image.
%
%    o metric: the metric.
%
%    o exception: Return any errors or warnings in this structure.
%
*/
MagickExport double *GetImageChannelDistortions(Image *image,
  const Image *reconstruct_image,const MetricType metric,
  ExceptionInfo *exception)
{
  double
    *channel_distortion;

  MagickBooleanType
    status;

  size_t
    length;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(reconstruct_image != (const Image *) NULL);
  assert(reconstruct_image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if ((reconstruct_image->columns != image->columns) ||
      (reconstruct_image->rows != image->rows))
    {
      (void) ThrowMagickException(&image->exception,GetMagickModule(),
        ImageError,"ImageSizeDiffers","`%s'",image->filename);
      return((double *) NULL); 
    }
  /*
    Get image distortion.
  */
  length=AllChannels+1UL;
  channel_distortion=(double *) AcquireQuantumMemory(length,
    sizeof(*channel_distortion));
  if (channel_distortion == (double *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
  (void) ResetMagickMemory(channel_distortion,0,length*
    sizeof(*channel_distortion));
  switch (metric)
  {
    case AbsoluteErrorMetric:
    {
      status=GetAbsoluteError(image,reconstruct_image,AllChannels,
        channel_distortion,exception);
      break;
    }
    case