[vtkusers] remove vtkImageBlend item

[Mauro Maiorca]

Hi David,

thanks for your clear and detailed explanation.

cheers,
Mauro

On Mon, Feb 7, 2011 at 6:19 PM, David Gobbi <david.gobbi at gmail.com> wrote:
> Hi Mauro,
>
> The answer is that it makes no difference to the efficiency.
> Each time the filter executes, it does the following:
> - it copies the first input to the output
> - it blends all the other inputs into the output, one by one
>
> It doesn't matter if you remove and re-add the first input versus
> whether you just change around the other inputs.  It will take the
> same amount of time to execute in each case.
>
> Also, I'm fairly sure you understand this next point, but just in
> case, here it is: calling AddInputConnection does not cause the
> filter to execute, it only makes a connection.
>
>  - David
>
>
> On Sun, Feb 6, 2011 at 10:56 PM, Mauro Maiorca <mauromaiorca at gmail.com> wrote:
>> Hi David,
>>
>> sorry, I wasn't clear enough, I'll try again.
>> Suppose I've got a big image, and I have to add/remove little objects
>> in just one little area of the image (thus leaving most of the image
>> as it was). My concern is whether in this particular case it's more
>> efficient to RemoveAllInputs and add all them again (including the big
>> image) or removing/re-adding just the little objects (without
>> removing/re-adding the big image)?
>>
>> cheers,
>> Mauro
>>
>>
>> On Fri, Feb 4, 2011 at 3:13 AM, David Gobbi <david.gobbi at gmail.com> wrote:
>>> Hi Mauro,
>>> I'm not quite sure what you mean.  Calling GetOutputPort() doesn't
>>> cause anything to happen, all it does is return a handle that can be
>>> used to make a pipeline connection.  Nothing is loaded until the
>>> pipeline is executed, and even then VTK uses timestamps to make
>>> sure that the data will only be loaded once.
>>>  - David
>>>
>>> On Thu, Feb 3, 2011 at 8:18 AM, Mauro Maiorca <mauromaiorca at gmail.com>
>>> wrote:
>>>>
>>>> Hi David,
>>>>
>>>> thank you very much for your quick reply and your clarification! It
>>>> makes all sense now, and it works!
>>>> But, how can I keep track of a particular object, then?
>>>> I don't mind redrawing all the canvas, but I'm concerned about a
>>>> reasonably big image (i.e. up to 4096x4096 pixel): I assume each call
>>>> to blend->AddInputConnection(0,color->GetOutputPort()) will re-load
>>>> the whole image, unless AddInputConnection has a really smart
>>>> buffering policy (is it the case?).
>>>>
>>>> cheers,
>>>> Mauro
>>>
>>
>