[Insight-users] Problems with ImageMaskSpatialObject

[Markus Mehrwald]

Hi,

I just had a look at the code of the ImageSpatialObject. In the method 
SetImage there is code to compute the offset of the spatial object. In 
my mind it should be better to use the index of the RequestedRegion 
instead of the origin because in my case this is the image I want the 
spatial object from. In case of having the whole image origin and the 
index of the RequestedRegion are the same anyway.

Regards,
Markus Mehrwald

Markus Mehrwald schrieb:
> Hi Julien,
>
> I do not really need ValueAt() at the moment. I used this code just 
> for debug reasons. As I wrote before I have created my binary image 
> first and than want it as spatial object to save it because if I only 
> save the image the translation information is gone. At the moment I 
> need ValueAt() I do not have the translation information anymore 
> (after a restart of the application and without calculating everything 
> again).
> I have tried some other things with transform and offsets but the only 
> case in which I get the correct result (but without translation) is if 
> the image passed to the ImageMaskSpatialObject has its origin at 0,0.
>
> Greetings,
> Markus
>
> Julien Jomier schrieb:
>> Hi Markus,
>>
>> Can you take into account the origin of your image when you request 
>> the ValueAt()?
>> If you are using the SpatialObjectToImageFilter to create your binary 
>> image you can set the origin of the output image, if you set it to 
>> the same origin as the input image then it should work.
>>
>> One other option is to reset the IndexToObjectTransform of your 
>> ImageMaskSpatialObject with an offset of zero:
>>
>>   myImageSO->GetIndexToObjectTransform()->SetOffset( offset );
>>   myImageSO->ComputeObjectToParentTransform();
>>
>> This will not modify the origin of the image passed using the 
>> SetImage() function so you can use it later.
>>
>> Hope that helps,
>>
>> Julien
>>
>> Markus Mehrwald wrote:
>>> Hi,
>>>
>>> I found the problem. The image starts at 180, 130 and that is the 
>>> problem. If I translate the image to 0, 0 the code from my last mail 
>>> works correct. The problem now: I need the information of the 
>>> translation for further calculations.
>>> Any suggestions how to keep the translation? I tried
>>>
>>> ImageMaskSpatialObjectType::TransformType::OffsetType offset;
>>> offset[0] = 
>>> thresholder->GetOutput()->GetRequestedRegion().GetIndex()[0];
>>> offset[1] = 
>>> thresholder->GetOutput()->GetRequestedRegion().GetIndex()[1];
>>> imageMaskSpatialObject->GetObjectToParentTransform()->SetOffset(offset); 
>>>
>>> imageMaskSpatialObject->ComputeObjectToParentTransform();
>>>
>>> but this leads to the same problem I had before. Also with 
>>> WorldTransform.
>>>
>>> Greetings,
>>> Markus
>>>
>>> Markus Mehrwald schrieb:
>>>> Hi,
>>>> I just implemented some code which uses a ImageMaskSpatialObject. I 
>>>> created a binary image in my filter chain and want this now to be a 
>>>> spatial object so I use the SetImage method of the spatial object 
>>>> but nothing happens. The output of the object looks good. 
>>>> Coordinates (, ...) are correct but at every point of the so 
>>>> created object ValueAt gives me 0. The code looks like the following:
>>>>
>>>> thresholder->Update();
>>>> ImageMaskSpatialObjectType::PointType point;
>>>> imageMaskSpatialObject = ImageMaskSpatialObjectType::New();
>>>> imageMaskSpatialObject->SetImage(thresholder->GetOutput());
>>>> imageMaskSpatialObject->SetRequestedRegion(thresholder->GetOutput()->GetRequestedRegion()); 
>>>>
>>>> imageMaskSpatialObject->Update();
>>>> imageMaskSpatialObject->UpdateOutputInformation();
>>>> imageMaskSpatialObject->ComputeObjectToWorldTransform();
>>>> double ret;
>>>> for (int i = 0; i < 640; i++)
>>>> {
>>>>    for (int j = 0; j < 512; j++)
>>>>    {
>>>>        point[0] = i;
>>>>        point[1] = j;
>>>>        imageMaskSpatialObject->ValueAt(point, ret);
>>>>        if (ret != 0)
>>>>            std::cout << "ret: " << ret << std::endl;
>>>>    }
>>>> }
>>>>
>>>>
>>>> The image coming from the thresholder has indeed a size of 300x280 
>>>> but changing the for-loops has no consequence on the outcome.
>>>> I took a look at the image coming from the thresholder and it is 
>>>> what it should be, a binary image with white areas too. The code 
>>>> above never writes anything to the standard output because it does 
>>>> not find any values differing to 0.
>>>> Did I anything wrong or is it a problem of the ImageMaskSpatialObject?
>>>>
>>>> Thanks in advance,
>>>> Markus
>>>> _______________________________________________
>>>> Insight-users mailing list
>>>> Insight-users at itk.org
>>>> http://www.itk.org/mailman/listinfo/insight-users
>>>
>>>
>>
>
>


-- 
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Cand. Dipl.-Inf. Med. Markus Mehrwald
Institut für Prozessrechentechnik, Automation und Robotik

Universität Karlsruhe (TH)
Gebäude 40.28
Engler-Bunte-Ring 8
76131 Karlsruhe

E-Mail: mehrwald at ira.uka.de
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