MagickExport MagickBooleanType SetImageType(Image *image,const ImageType type)
{
  const char
    *artifact;

  ImageInfo
    *image_info;

  MagickBooleanType
    status;

  QuantizeInfo
    *quantize_info;

  assert(image != (Image *) NULL);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"...");
  assert(image->signature == MagickSignature);
  status=MagickTrue;
  image_info=AcquireImageInfo();
  image_info->dither=image->dither;
  artifact=GetImageArtifact(image,"dither");
  if (artifact != (const char *) NULL)
    (void) SetImageOption(image_info,"dither",artifact);
  switch (type)
  {
    case BilevelType:
    {
      if (SetImageMonochrome(image,&image->exception) == MagickFalse)
        {
          status=TransformImageColorspace(image,GRAYColorspace);
          (void) NormalizeImage(image);
          quantize_info=AcquireQuantizeInfo(image_info);
          quantize_info->number_colors=2;
          quantize_info->colorspace=GRAYColorspace;
           status=QuantizeImage(quantize_info,image);
           quantize_info=DestroyQuantizeInfo(quantize_info);
         }
      status=AcquireImageColormap(image,2);
       image->matte=MagickFalse;
       break;
     }
    case GrayscaleType:
    {
      if (SetImageGray(image,&image->exception) == MagickFalse)
        status=TransformImageColorspace(image,GRAYColorspace);
      image->matte=MagickFalse;
      break;
    }
    case GrayscaleMatteType:
    {
      if (SetImageGray(image,&image->exception) == MagickFalse)
        status=TransformImageColorspace(image,GRAYColorspace);
      if (image->matte == MagickFalse)
        (void) SetImageAlphaChannel(image,OpaqueAlphaChannel);
      break;
    }
    case PaletteType:
    {
      if (IssRGBCompatibleColorspace(image->colorspace) == MagickFalse)
        status=TransformImageColorspace(image,sRGBColorspace);
      if ((image->storage_class == DirectClass) || (image->colors > 256))
        {
          quantize_info=AcquireQuantizeInfo(image_info);
          quantize_info->number_colors=256;
          status=QuantizeImage(quantize_info,image);
          quantize_info=DestroyQuantizeInfo(quantize_info);
        }
      image->matte=MagickFalse;
      break;
    }
    case PaletteBilevelMatteType:
    {
      if (IssRGBCompatibleColorspace(image->colorspace) == MagickFalse)
        status=TransformImageColorspace(image,sRGBColorspace);
      if (image->matte == MagickFalse)
        (void) SetImageAlphaChannel(image,OpaqueAlphaChannel);
      (void) BilevelImageChannel(image,AlphaChannel,(double) QuantumRange/2.0);
      quantize_info=AcquireQuantizeInfo(image_info);
      status=QuantizeImage(quantize_info,image);
      quantize_info=DestroyQuantizeInfo(quantize_info);
      break;
    }
    case PaletteMatteType:
    {
      if (IssRGBCompatibleColorspace(image->colorspace) == MagickFalse)
        status=TransformImageColorspace(image,sRGBColorspace);
      if (image->matte == MagickFalse)
        (void) SetImageAlphaChannel(image,OpaqueAlphaChannel);
      quantize_info=AcquireQuantizeInfo(image_info);
      quantize_info->colorspace=TransparentColorspace;
      status=QuantizeImage(quantize_info,image);
      quantize_info=DestroyQuantizeInfo(quantize_info);
      break;
    }
    case TrueColorType:
    {
      if (IssRGBCompatibleColorspace(image->colorspace) == MagickFalse)
        status=TransformImageColorspace(image,sRGBColorspace);
      if (image->storage_class != DirectClass)
        status=SetImageStorageClass(image,DirectClass);
      image->matte=MagickFalse;
      break;
    }
    case TrueColorMatteType:
    {
      if (IssRGBCompatibleColorspace(image->colorspace) == MagickFalse)
        status=TransformImageColorspace(image,sRGBColorspace);
      if (image->storage_class != DirectClass)
        status=SetImageStorageClass(image,DirectClass);
      if (image->matte == MagickFalse)
        (void) SetImageAlphaChannel(image,OpaqueAlphaChannel);
      break;
    }
    case ColorSeparationType:
    {
      if (image->colorspace != CMYKColorspace)
        {
          if (IssRGBCompatibleColorspace(image->colorspace) == MagickFalse)
            (void) TransformImageColorspace(image,sRGBColorspace);
          status=TransformImageColorspace(image,CMYKColorspace);
        }
      if (image->storage_class != DirectClass)
        status=SetImageStorageClass(image,DirectClass);
      image->matte=MagickFalse;
      break;
    }
    case ColorSeparationMatteType:
    {
      if (image->colorspace != CMYKColorspace)
        {
          if (IssRGBCompatibleColorspace(image->colorspace) == MagickFalse)
            (void) TransformImageColorspace(image,sRGBColorspace);
          status=TransformImageColorspace(image,CMYKColorspace);
        }
      if (image->storage_class != DirectClass)
        status=SetImageStorageClass(image,DirectClass);
      if (image->matte == MagickFalse)
        (void) SetImageAlphaChannel(image,OpaqueAlphaChannel);
      break;
    }
    case OptimizeType:
    case UndefinedType:
      break;
  }
  image_info=DestroyImageInfo(image_info);
  if (status == MagickFalse)
    return(MagickFalse);
  image->type=type;
  return(MagickTrue);
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.