[vtkusers] double vtkDataArray::GetTuple1(vtkIdType i) vs void vtkDataArray::GetTuple(vtkIdType i, double *tuple)

[David Gobbi]

Hi Maarten,

The first thing you'd have to do, of course, is split the data into
two data sets, each with a single array.  Then you can use filters to
combine them back into a single RGB image that you can feed into
the texture.  Take a look at vtkImageMapToColors, vtkImageBlend,
vtkImageHSVToRGB, and use your imagination.  Or, you could write
your own filter that will take the two arrays and combine them to make
an RGB array.

  David


On Thu, May 8, 2014 at 10:08 AM, Maarten Beek <beekmaarten at yahoo.com> wrote:
> Your suggestions helped fix me my bug!
>
> I'll try your iterator. Maybe I can improve the speed of my algorithm with
> it.
>
>
> On a different note:
> Any ideas/suggestions on the display 2 data arrays in an vtkImageData at the
> same time? I would like an intensity image coloured by the input flag I (we)
> just added. A drr with multiple bones in which each bone has its own colour.
> Depending on which data array I use in vtkTexture I now see an intensity
> (xray) image or solid coloured bones. Should I create separate mask images
> and use them to show a transparent colour on top of the intensity image? or
> use stencils?
>
> Thanks - Maarten
>
>
> On Thursday, May 8, 2014 11:11:55 AM, David Gobbi <david.gobbi at gmail.com>
> wrote:
> Hi Maarten,
>
> I actually did write an iterator with such a function, but I never got
> around to contributing it to VTK.  I called it vtkImageRegionIterator.
> The source code is here:
> http://github.com/dgobbi/AIRS/tree/master/ImageSegmentation
>
> It has three separate inline methods for getting the voxel:
> GetIndexX(), GetIndexY(), GetIndexZ().
>
> A couple years ago I had some big plans for improving the VTK
> image iterators, but like so many things, there was never enough
> time.
>
>   David
>
>
>
> On Thu, May 8, 2014 at 7:20 AM, Maarten Beek <beekmaarten at yahoo.com> wrote:
>> Hi David,
>>
>> Thanks so much for your clarification!
>> I did see issues in the resulting image but was attributing them to noise
>> in
>> the original images. Now I see my code just had a huge bug in it.
>>
>> I guess I would need a row counter in order to initialize voxelid
>> correctly.
>>
>> Wouldn't it be nice if the image iterator had a function like getVoxel(int
>> ijk[3])...? I believe ITK has such an iterator.
>>
>> Maarten
>>
>>
>> On Wednesday, May 7, 2014 5:26:23 PM, David Gobbi <david.gobbi at gmail.com>
>> wrote:
>> I should add: you actually have to re-initialize the voxelid at the
>> beginning of each row (i.e. at the beginning of each span of the
>> iterator).
>>
>> On Wed, May 7, 2014 at 3:22 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>> Hi Maarten,
>>>
>>> Since you know it's a vtkUnsignedCharArray, you shouldn't be using
>>> the SetTuple/GetTuple methods.  Use the SetTupleValue and
>>> GetTupleValue methods, they're much faster because 1) they aren't
>>> virtual methods and 2) they don't have to convert to/from double.
>>> Or even better, if you know that your array only has one component,
>>> you can use SetValue/GetValue.
>>>
>>> Your math for voxelid is too simplistic.  Depending on how the update
>>> extent is divided amongst the threads, it might give you a location
>>> that is totally wrong.  To see why, draw a square on a piece of paper.
>>> That square represents the total extent of the output.  Then divide
>>> that square into quadrants, and imagine that each quadrant goes
>>> to a different Execute method.  Then think about how each thread
>>> is going to march through the data.
>>>
>>>  David
>>>
>>>
>>> On Wed, May 7, 2014 at 2:20 PM, Maarten Beek <beekmaarten at yahoo.com>
>>> wrote:
>>>> Hi all,
>>>>
>>>> I experienced a crash in my algorithm derived from
>>>> vtkThreadedImageAlgorithm, that (I think) I solved, but that I don't
>>>> understand. Is there some one who can shed some light on the following?
>>>>
>>>> What I am trying to do is adding a flag identifying the input(s) that
>>>> contribute to the value of each pixel in the output image
>>>>
>>>>
>>>>
>>>> //----------------------------------------------------------------------------
>>>> // This templated function executes the filter for any type of data.
>>>> template <class OT>
>>>> void cmvtkTemplatedExecute(cmvtkDRRGenerator2* self,
>>>>                                vtkDataSetCollection* inputs,
>>>> vtkImageData*
>>>> output,
>>>>                                int extent[6], int threadId, OT*)
>>>> {
>>>>    vtkUnsignedCharArray* uchararray =
>>>>
>>>>
>>>> vtkUnsignedCharArray::SafeDownCast(output->GetPointData()->GetScalars("input_flag"));
>>>>
>>>>    int numinputs = inputs->GetNumberOfItems();
>>>>    for( int input_i = 0; input_i < numinputs; ++input_i )
>>>>    {
>>>>        vtkImageData* input =
>>>> vtkImageData::SafeDownCast(inputs->GetItem(input_i));
>>>>        if( 0 == input )
>>>>        {
>>>>            // should not happen
>>>>            continue;
>>>>        }
>>>>        const int* dims= output->GetDimensions();
>>>>
>>>>        vtkImageProgressIterator<OT> outIt(output, extent, self,
>>>> threadId);
>>>>        vtkIdType voxelid = extent[0] + size[0]*extent[2] +
>>>> size[0]*size[1]*extent[4];
>>>>
>>>>        // Loop through output pixels
>>>>        while( !outIt.IsAtEnd() )
>>>>        {
>>>>            OT* outSI = outIt.BeginSpan();
>>>>            OT* outSIEnd = outIt.EndSpan();
>>>>
>>>>            while( outSI != outSIEnd )
>>>>            {
>>>>                // start with setting pixel to 0.0
>>>>                if( input_i == 0 )
>>>>                {
>>>>                    *outSI = 0.0;
>>>>                }
>>>>
>>>>                OT result = 0.0;
>>>>
>>>>                //.... some math resulting in a value for result....
>>>>
>>>>                *outSI += result;
>>>>
>>>>                // this input image participates in voxel values; adjust
>>>> bit
>>>>                if( 0.0 < result && 0 != uchararray )
>>>>                {
>>>>                    // The commented code crashes...
>>>>
>>>>                    //unsigned char oldvalue =
>>>> uchararray->GetTuple1(voxelid);
>>>>                    //unsigned char newvalue = oldvalue | (1<<input_i);
>>>>                    //uchararray->SetTuple1(voxelid, newvalue);
>>>>
>>>>                    double dOldValue;
>>>>                    uchararray->GetTuple(voxelid, &dOldValue);
>>>>                    unsigned char chOldValue = static_cast<unsigned
>>>> char>(dOldValue);
>>>>                    unsigned char chNewValue = chOldValue | (1<<input_i);
>>>>                    double dNewValue = static_cast<double>(chNewValue);
>>>>                    uchararray->SetTuple(voxelid, &dNewValue);
>>>>                }
>>>>
>>>>                ++outSI;
>>>>                ++voxelid;
>>>>            }
>>>>            outIt.NextSpan();
>>>>        }
>>>>    } // input_i < numinputs
>>>> }
>>
>>
>
>