Posted by
Gluender-2 on
Mar 31, 2009; 8:36am
URL: http://imagej.273.s1.nabble.com/Contradiction-with-show-method-tp3693120p3693130.html
David,
without going into the details of your problem, what you are
experiencing is a peculiarity of the OO-trend in general and of Java
(as an OO-language) in your specific situation.
Objects in the first place have the property to exist and, well, only
in the second place they may evolve or change...
That said, procedures, such as those characteristic for signal
processing tasks, must cope with the (in principle) parallel
existence of objects in time.
Now why are people using OO-languages to solve procedural problems?
In the specific case because Java is, to a certain extent, platform
independent.
In general, because OO-languages are modern and under many
circumstances easier to handle.
Finally and quite important they allow for easier parallelisation of
tasks, a property that in turn results from the more or less timeless
parallel existence of objects.
All that means for your problem that you have to take care for the
correct sequence of what is handled in different threads which
implies that you first need to know what is handle in different
threads. Java provides tools for both but their application is
sometimes a bit tricky.
>To All,
>
>Wilhelm, I reran my tests and got the same results. Howeve, I should have
>included my case 2 as a normal result. Only case 1 seems to be odd. For what
>it's worth, I am using IJ 1.42k.
>
>Micheal, I am running Windows XP2002 SP3. I am using a Pentim 4 from 2005,
>that is only a single core. I don't know if it mutithreds or not.
>David
Please note that multiple threads do not imply their distribution to
several processors.
Best
Herbie
>On Mon, Mar 30, 2009 at 1:26 AM, Michael Schmid
><
[hidden email]>wrote:
>
>> Hi David,
>>
>> Java is multi-threaded; displaying images is usually done in a separate
>> thread. Especially on multiprocessor machines, this improves performance.
>>
>> Thus, it can easily happen that "im1.show();" displays the image a few
>> thenths of a second after that method is called; at that time the data are
>> modified already.
>>
>> (not a bug, a feature ;-)
>>
>> Michael
>> ________________________________________________________________
>>
>>
>> On 29 Mar 2009, at 22:34, David William Webster wrote:
>>
>> I am learning Java via th "monkey see, monkey do" method and get what seems
>>> to be a contradiction.
>>>
>>> I ran a test similar to the one shown in Burger and Berge on page 502.(see
>>> run method below). Without the updateAndDraw(), the invert()
>>> result should not be display'ed. But,
>>> In case 1, with the wait(2000) and updateAndDraw() commented out,
>>> I get the inverted image being displayed (It shouldn't be).
>>> In case 2, I use the wait(200) and get only the original image being
>>> displayed.
>>> In case 3, I add the updateAndDraw() and get the inverted image.
>>> Only case 3 makes any sense
>>>
>>>
>>> public void run(ImageProcessor ip) {
>>>
>>> ImageProcessor ip1 = ip.duplicate();
>>> ImagePlus im1 = new ImagePlus("im1",ip1);
>>> im1.show();
>>> //IJ.wait(2000);
>>> ip1.invert();
>>> //im1.updateAndDraw();
>>> }
>>>
> >> David Webster