[vtkusers] why my computing gray scale histogram of DICOM files is different from mimics

[David Gobbi]

Two differences:

1) MIMICS is showing a log plot
2) The plot is shifted by the RescaleIntercept


On Sun, Aug 14, 2016 at 9:52 AM, Liu_tj <tjlp at netease.com> wrote:

> Hi,
>
> I try to get the grayscale of points in DICOM files and draw the histogram
> using .NET component, and what I get is different from the histogram of
> MIMICS. My C# code is as follow, the returned vtkLongArray stores the
> grayscale statistic result, value of element is the total number of the
> point whose gray scale value is equal to the array index:
>
> public vtkLongArray GetGreyScaleStatisticsFromImageData(vtkImageData
> data, out long min_grey, out long max_grey)
> {
>             vtkImageExtractComponents extract =
> vtkImageExtractComponents.New();
>             extract.SetInputData(data);
>             extract.SetComponents(0);
>             extract.Update();
>
>             double[] scalarrange = extract.GetOutput().GetScalarRange();
>             min_grey = (long)scalarrange[0];
>             max_grey = (long)scalarrange[1];
>             long size = (long)(scalarrange[1] - scalarrange[0]);
>             vtkImageAccumulate histogram = vtkImageAccumulate.New();
>             histogram.SetInputConnection(extract.GetOutputPort());
>             histogram.SetComponentExtent((int)min_grey, (int)max_grey, 0,
> 0, 0, 0);
>             histogram.SetComponentOrigin(0, 0, 0);
>             histogram.SetComponentSpacing(1, 0, 0);
>             histogram.SetIgnoreZero(1);
>             histogram.Update();
>             vtkLongArray count = vtkLongArray.New();
>             count.SetNumberOfComponents(1);
>             count.SetNumberOfTuples(size);
>             IntPtr value = histogram.GetOutput().GetScalarPointer();
>             string scalartype = histogram.GetOutput().
> GetScalarTypeAsString();
>             int s = histogram.GetOutput().GetScalarSize();
>             long[] managedValArray = new long[size];
>             Marshal.Copy(value, managedValArray, 0,
> managedValArray.Length);
>             for(int i=0; i<managedValArray.Length; i++)
>             {
>                 count.SetTuple1(i, managedValArray[i]);
>             }
>             return count;
> }
>
> The images of my and MIMICS are attached.
>
> Does any guys know that?
>
> Thanks
> Liu Peng
>
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