[vtkusers] How to map negative grayscale to color?
David Gobbi
david.gobbi at gmail.com
Wed Mar 9 11:11:02 EST 2016
Hi Liu Peng,
I'm glad to hear it worked for you. I didn't think it would be necessary,
because I thought that if you passed an RGB (or RGBA) image to
vtkImageViewer2 it would simply display it as-is, without needing any
tweaks to internal parts of the Viewer (note: I hardly ever use
vtkImageViewer or vtkimageViewer2 myself, I prefer to use the image mappers
directly instead).
- David
On Wed, Mar 9, 2016 at 8:21 AM, Liu_tj <tjlp at netease.com> wrote:
> Hi, David,
>
> I try it again. The conversion from gray scale to RGB works after I set
> the LookupTable to vtkImageMapToWindowLevelColors returned by
> vtkImageViewer2::GetWindowLevels().
>
>
>
> 在2016-03-09，"David Gobbi" <david.gobbi at gmail.com> 写道：
>
> -----原始邮件-----
> *发件人:*"David Gobbi" <david.gobbi at gmail.com>
> *发送时间:*2016年03月9日 星期三
> *收件人:*"Liu_tj" <tjlp at netease.com>
> *抄送:*"vtkusers" <vtkusers at vtk.org>
> *主题:*Re: Re: Re: Re: [vtkusers] How to map negative grayscale to color?
>
>
> No, that isn't necessary.
>
> On Tue, Mar 8, 2016 at 9:29 PM, Liu_tj <tjlp at netease.com> wrote:
>
>> Hi,David,
>>
>> Do I need to set the LookupTable to vtkImageMapToWindowLevelColors which
>> is returned by vtkImageViewer2::GetWindowLevels() instead of create a new
>> vtkImageMapToColors?
>>
>> BR,
>> Thanks
>>
>>
>> 在2016-03-09，"David Gobbi" <david.gobbi at gmail.com> 写道：
>>
>> -----原始邮件-----
>> *发件人:*"David Gobbi" <david.gobbi at gmail.com>
>> *发送时间:*2016年03月9日 星期三
>> *收件人:*"Liu_tj" <tjlp at netease.com>
>> *主题:*Re: Re: Re: [vtkusers] How to map negative grayscale to color?
>>
>>
>> Hi Liu Peng,
>>
>> Do you want to show a gray image underneath, and the color image
>> on top? I'm not sure if vtkImageViewer works property if you add
>> more than one image.
>>
>> You should add a "print" statement of some kind to your code to
>> print the values of scalarrange, to be sure they are correct.
>>
>> Don't call colormap.Build() after setting your own values for the table,
>> or it might overwrite the values that you have set. If you call it at
>> all,
>> call it immediately after SetNumberOfTableValues(), before you set
>> any of your own values.
>>
>> The range on the final for() loop should be the following:
>> for (int i = (int)(threshhold[1]) + 1; i <= (int)(scalarrange[1]); i++)
>>
>> Also, if you want the beyond-threshold values to be transparent
>> instead of black, then set the alpha component to zero:
>>
>> for (int i = (int)(scalarrange[0]); i < (int)(threshhold[0]); i++)
>> {
>> colormap.SetTableValue(i - (int)scalarrange[0], 0.0, 0.0, 0.0, 0.0);
>> }
>>
>> - David
>>
>>
>> On Tue, Mar 8, 2016 at 9:40 AM, Liu_tj <tjlp at netease.com> wrote:
>>
>>> Hi, David,
>>>
>>> I follow your post and it doesn't work. The DICOM image shows no color,
>>> just gray image. Could you have a look at my code below? I use a
>>> vtkImageView2 to display the DICOM image. The code is c# by Activiz .NET.
>>> The scalar range of test image is [-1024,3071]. I want to show the gray
>>> scale at [1000,3000] to green. The function GrayToColors() maps gray scale
>>> to color, it is called by Display().
>>>
>>> private void Display(vtkRenderWindow aRenderWindow, vtkAlgorithmOutput
>>> aData)
>>> {
>>> if (aData == null)
>>> return;
>>>
>>> m_imageViewer = vtkImageViewer2.New();
>>> m_imageViewer.SetInputConnection(aData);
>>> switch (m_sliceDirection)
>>> {
>>> case Direction.AXIAL:
>>> m_imageViewer.SetSliceOrientationToXY();
>>> break;
>>> case Direction.CORONAL:
>>> m_imageViewer.SetSliceOrientationToYZ();
>>> break;
>>> case Direction.SAGITTAL:
>>> m_imageViewer.SetSliceOrientationToXZ();
>>> break;
>>> default:
>>> break;
>>> }
>>>
>>> m_imageViewer.GetSliceRange(ref m_minSliceNumber, ref
>>> m_maxSliceNumber);
>>> m_interactorStyle = vtkInteractorStyleImage.New();
>>> m_interactorStyle.MouseWheelForwardEvt += new
>>> vtkObject.vtkObjectEventHandler(interactor_MouseWheelForwardEvt);
>>> m_interactorStyle.MouseWheelBackwardEvt += new
>>> vtkObject.vtkObjectEventHandler(interactor_MouseWheelBackwardEvt);
>>>
>>>
>>> aRenderWindow.GetInteractor().SetInteractorStyle(m_interactorStyle);
>>> aRenderWindow.GetRenderers().InitTraversal();
>>>
>>> m_renderer = aRenderWindow.GetRenderers().GetFirstRenderer();
>>> m_renderer.SetBackground(0.0, 0.0, 0.0);
>>>
>>> m_imageViewer.SetRenderWindow(aRenderWindow);
>>> m_currentSlice = m_minSliceNumber + (m_maxSliceNumber -
>>> m_minSliceNumber) / 2;
>>> m_imageViewer.SetSlice(m_currentSlice);
>>>
>>> double[] scalarrange = new double[2];
>>> scalarrange = m_imageViewer.GetInput().GetScalarRange();
>>> double[] threshhold = new double[2];
>>> threshhold[0] = 1000;
>>> threshhold[1] = 3000;
>>> m_imageViewer.Render();
>>> GrayToColors(m_renderer, aData, scalarrange, threshhold);
>>>
>>> m_imageViewer.Render();
>>> }
>>>
>>> private void GrayToColors(vtkRenderer renderer,
>>> vtkAlgorithmOutput data, double[] scalarrange, double[] threshhold)
>>> {
>>> vtkLookupTable colormap = vtkLookupTable.New();
>>> int number = (int)(scalarrange[1] - scalarrange[0] + 1);
>>> colormap.SetRange(scalarrange[0], scalarrange[1]);
>>> colormap.SetNumberOfTableValues(number);
>>>
>>> for (int i = (int)(scalarrange[0]); i <
>>> (int)(threshhold[0]); i++)
>>> {
>>> colormap.SetTableValue(i - (int)scalarrange[0], 0.0,
>>> 0.0, 0.0, 1.0);
>>> }
>>> for (int i = (int)(threshhold[0]); i <=
>>> (int)(threshhold[1]); i++)
>>> {
>>> colormap.SetTableValue(i - (int)scalarrange[0], 0.0,
>>> 1.0, 0.0, 1.0);
>>> }
>>> for (int i = (int)(threshhold[1]); i <
>>> (int)(scalarrange[1]); i++)
>>> {
>>> colormap.SetTableValue(i - (int)scalarrange[0], 0.0,
>>> 0.0, 0.0, 1.0);
>>> }
>>> colormap.Build();
>>>
>>> vtkImageMapToColors colormapper = vtkImageMapToColors.New();
>>> colormapper.SetInputConnection(data);
>>> colormapper.SetLookupTable(colormap);
>>> colormapper.Update();
>>>
>>> vtkImageActor colormapActor = vtkImageActor.New();
>>> colormapActor.SetInput(colormapper.GetOutput());
>>> renderer.AddActor(colormapActor);
>>> renderer.ResetCamera();
>>> renderer.Modified();
>>> }
>>>
>>> Thanks
>>>
>>> 在2016-03-08，"David Gobbi" <david.gobbi at gmail.com> 写道：
>>>
>>> -----原始邮件-----
>>> *发件人:*"David Gobbi" <david.gobbi at gmail.com>
>>> *发送时间:*2016年03月8日 星期二
>>> *收件人:*"Liu_tj" <tjlp at netease.com>
>>> *抄送:*"vtkusers" <vtkusers at vtk.org>
>>> *主题:*Re: Re: [vtkusers] How to map negative grayscale to color?
>>>
>>>
>>> Hi Liu Pen,
>>>
>>> That's because I forgot to include the index argument in the call to
>>> SetTableValue:
>>>
>>> table->SetRange(-1024, 4095);
>>> table->SetNumberOfTableValues(4095 + 1024 + 1);
>>> for (int i = -1024; i < -10; i++) {
>>> table->SetTableValue(i + 1024, 0.0, 0.0, 0.0, 1.0);
>>> }
>>>
>>> The table index must start at zero. The call to SetRange(-1024, 4095)
>>> causes the scalar value -1024 to map to table index 0. In the "for" loop,
>>> i is the scalar value.
>>>
>>> - David
>>>
>>>
>>> On Tue, Mar 8, 2016 at 7:27 AM, Liu_tj <tjlp at netease.com> wrote:
>>>
>>>> Hi, David,
>>>>
>>>> When I try, a lot of errors are popup: "Can't set the table value for
>>>> negative index".
>>>>
>>>> Seems the negative grayscale needs some transformation.
>>>>
>>>> Thanks
>>>> Liu Peng
>>>>
>>>>
>>>> 在2016-03-08，"David Gobbi" <david.gobbi at gmail.com> 写道：
>>>>
>>>> -----原始邮件-----
>>>> *发件人:*"David Gobbi" <david.gobbi at gmail.com>
>>>> *发送时间:*2016年03月8日 星期二
>>>> *收件人:*"Liu_tj" <tjlp at netease.com>
>>>> *抄送:*"vtkusers" <vtkusers at vtk.org>
>>>> *主题:*Re: [vtkusers] How to map negative grayscale to color?
>>>>
>>>> Hi Liu Peng,
>>>>
>>>> You can set individual values in the lookup table,
>>>> in order to precisely map certain scalar values to
>>>> specific colors:
>>>>
>>>> table->SetRange(-1024, 4095);
>>>> table->SetNumberOfTableValues(4095 + 1024 + 1);
>>>> for (int i = -1024; i < -10; i++) {
>>>> table->SetTableValue(0.0, 0.0, 0.0, 1.0);
>>>> }
>>>> for (int i = -10; i <= 200; i++) {
>>>> table->SetTableValue(0.0, 1.0, 0.0, 1.0);
>>>> }
>>>> etcetera.
>>>>
>>>> - David
>>>>
>>>>
>>>> On Mon, Mar 7, 2016 at 9:31 AM, Liu_tj <tjlp at netease.com> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> I try to use the vtkLookupTable to convert the grayscale to rgb color.
>>>>> The image scalar range is [-1024,3071] returned by
>>>>> vtkImageData::GetScalarRange(). Now I want to convert specific grayscale
>>>>> range, for example, [-10,200] to one color, such as green (RGB is 0,1,0).
>>>>> How to do that by vtkLookupTable? I have no idea what method should call:
>>>>> SetNumberOfTableValues(), SetRange(), SetHueRange(), SetValueRange(). What
>>>>> do "Hue" and "Value" stand for?
>>>>>
>>>>> BR,
>>>>> Liu Peng
>>>>>
>>>>
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