Fwd: Image > Adjust > Size and undo buffer ?

[lechristophe]

Début du message transféré :

> Expéditeur: "Christophe L. " <[hidden email]>
> Date: 4 mars 2012 18:53:24 HNEC
> Destinataire: "<[hidden email]>" <[hidden email]>
> Objet: Rép : Image > Adjust > Size and undo buffer ?
>
> Hi Michael,
>
> Thanks for your input. You're right, the disk writing must be swapping from RAM. The 2.5 GB size is what is approximatively taken from the hard drive when resizing one image, with the "Average when downsizing" option. As Wayne pointed out, this correlates with the memory usage in the case of a 16k x 16k image, again incriminating memory swapping to the HD. As regards undo, thanks for the details, maybe someone from Fiji can clarify
> on the difference in the options ?
>
> Cheers,
>
> Christophe
>
> Le 4 mars 2012 à 18:02, Michael Schmid <[hidden email]> a écrit :
>
>> Hi Christophe,
>>
>> a few thoughts on this:
>>
>> ImageJ does not use the disk for undo buffers.
>> Your operating system may swap parts of the memory used by ImageJ or other
>> programs onto the harddisk if there is not enough space in RAM.  So, the
>> best strategy would be to have no other programs than ImageJ open while
>> handling large images (or buy more RAM).
>>
>> The "Keep multiple undo buffers" option only makes a difference if you
>> have several images open at the same time. If it is unchecked (which is
>> the default), selecting an image different from the current one deletes
>> the undo buffer of the image that goes to the background.
>>
>> I don't know why this option is not present in Fiji.  The only workaround
>> (without accessing it an a plugin) I see is opening your IJ_Prefs.txt file
>> with a text editor (while ImageJ is NOT running), locate the line starting
>> with
>> prefs.options=
>> and checking whether the number there is larger than 2^30 = 1073741824.
>> If it is, the "Keep multiple undo buffers" is enabled, and you can replace
>> it by the same number minus 1073741824 to disable that option.
>> Under Mac OS X, IJ_Prefs.txt is under the users Library/Preferences; under
>> Windows in the ImageJ Program directory.
>>
>> There is a Prefs setting, 'disableUndo', accessible from plugins, which
>> reduces the amount of memory needed for operations that do not require an
>> Undo Buffer for operation, such as the Process>Math operations and the
>> Rank Filters (mean, minimum, maximum, median).  I don't think that it
>> would help when resizing images, because the original image must be
>> present in memory anyhow until the smaller image has been created.
>>
>> An 8-bit image, 16k * 16k has 256 MB size; an RGB image 16k * 16 k has 1
>> GB.  If you have 2.5 GB, do you have a stack?  In ImageJ, there is no undo
>> on stacks anyhow, so Undo is not an issue.
>>
>> Hope this helps,
>>
>> Michael
>> ________________________________________________________________________
>>
>>
>>
>>
>> On Sun, March 4, 2012 10:49, Christophe Leterrier wrote:
>>> Hi,
>>>
>>> I'm currently working on a computer that has only a few free GB on its
>>> hard drive. I'm downsizing large images (16000x16000 px, 2.5 GB) and
>>> noticed that the free space on the HD seemed to drop by around the
>>> same amount (2.5 GB) when resizing an image. I guess it has to do with
>>> the undo buffer, because I found this in the IJ changelog :
>>>
>>> 1.45a 6 February 2011
>>> The Edit>Undo command is, in most cases, undoable.
>>> Added the "Keep multiple undo buffers" option to the
>>> Edit>Options>Memory dialog box.
>>>
>>> and
>>>
>>> 1.44f, 22 August 2010
>>> Thanks to Michael Schmid, Image>Adjust>Size and Image>Scale have
>>> "Average when downsizing" options and Image>Adjust>Size supports Undo.
>>>
>>> Is there any way to disable the undo buffer so that it doesn't write
>>> very large amounts of data to the HD (in general this seems to slows
>>> things a lot, when it's not just crashing because of my lack of free
>>> space)? As of IJ 1.46h on OSX (Fiji distro), I don't find the "Keep
>>> multiple undo buffers" option to the Edit>Options>Memory dialog box.
>>>
>>> Thanks for your help,
>>>
>>> Christophe
>>>