[vtkusers] Pass data in reader without copying?

[Elvis Stansvik]

2016-07-03 20:19 GMT+02:00 David Gobbi <david.gobbi at gmail.com>:

> On Sun, Jul 3, 2016 at 11:59 AM, Elvis Stansvik <
> elvis.stansvik at orexplore.com> wrote:
>
>> 2016-07-03 19:57 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>>
>>> If I'm writing my own custom volume reader, and I have the read data in
>>> memory (say as a float*). If I know the data is in the right format/layout,
>>> can I somehow pass ownership of that data to the output of the algorithm
>>> without incurring a copy?
>>>
>>> I've been looking at some of the simpler readers that come with VTK, but
>>> all of them seems to copy the read data to the output (?).
>>>
>>
>> Looking at vtkImageData, what I would like (I think) is some way of
>> setting the pointer that is returned by vtkImageData::GetScalarPointer.
>>
>
> Here is a cut & paste of code from vtkImageImport.  Read the the
> documentation for vtkAbstractArray::SetVoidArray() carefully.
>

Ah, thanks a lot. I should have found that.

Elvis


>
>   vtkImageData *data = vtkImageData::SafeDownCast(output);
>   data->SetExtent(0,0,0,0,0,0);
>   data->AllocateScalars(outInfo);
>   vtkIdType size = this->NumberOfScalarComponents;
>   size *= this->DataExtent[1] - this->DataExtent[0] + 1;
>   size *= this->DataExtent[3] - this->DataExtent[2] + 1;
>   size *= this->DataExtent[5] - this->DataExtent[4] + 1;
>   data->SetExtent(this->DataExtent);
>   data->GetPointData()->GetScalars()->SetVoidArray(inputPtr, size, 1);
>   data->GetPointData()->GetScalars()->SetName(this->ScalarArrayName);
>
>  - David
>
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