Fixed V4.25: Zooming can be really slow on Windows 7 x64

[trh]

Hi,

when I zoom into a jpg Image and the Image "internally" gets clipped because the full Image would be larger then screen resolution zooming gets really really slow. Zooming while the Image can be displayed in full on the screen is acceptably fast.

Example: If I selected a 100x100px rectangle from a 1439x1079px Image on my 1920x1200 desktop and zoom into it, it takes a full 27seconds on my quad-core machine to zoom in. While it's processing Irfanview uses one of the cores nearly at 100%. I didn't had this problem with Windows Vista/XP (x32), so I guess it's a Windows 7 only issue (maybe even only x64).

As a developer myself I'd be happy to try out debug-versions etc. if you can't find the problem directly.

Greetings

OS: Windows 7 x64
CPU: Q6600 Quad-Core
RAM: 4GB ~3GB free
Desktop: Dualscreen, each 1920x1200 (but the problem also happens when dual-screen is deactivated)
Bug Happens regardless of if Aero Glass or Basic is enabled.

[Mij]

DO you have Use resample for zooming checked or unchecked in View >Display options ?

[trh]

Yes, it is enabled - if it is disabled it is alot faster. I'm not sure if it was enabled or disabled on XP - i'll check tomorrow.

[trh]

I checked it on XP - it is enabled there too, but zooming is alot faster than under Windows 7 (delay less than 1 second when zooming gets larger than the screen itself), while under Windows 7 the same zoom takes up to 30 seconds.

[Skippybox]

Well, I'm glad I've got XP!

[Mij]

trh
You say that you did not notice this in Vista. Could you confirm that.

Resampling in Irfanview is actually very slow in Vista. A resample of one of my 10MP images at 300% zoom typically takes around 26 seconds on my machine.
Other programs seem to achieve the same result in a fraction of a second.

I have always assumed that Irfanview just used a particularly inefficient method to do the job, but if you are indeed seeing different speeds with different operating systems I begin to wonder if there is perhaps a bug in there.

[cwb3106]

Works Fine for Me on Vista x64

FWIW: zooming a 100x100 rectangle on a 1439x1000 image took less than 3 seconds on my system (Vista x64/quad-core I7/6GB).

[Mij]

That is interesting cwb3106.

With Use resampling for zoom checked my processor (Athlon64 X2 Dual Core 5000+ 2.60GHz) takes 19 seconds to do that task in Vista 32bit. It runs at 50% CPU usage throughout the task. I believe that only a single core is used, so that one is presumably running flat out for the whole time.

With resampling unchecked the zoom is of course virtually instantaneous.

[MItaly]

The problem with IV and resampling is that internally it resamples the whole image, and not just the portion you are watching; this means that if you zoom a 10 MP image to 800% just to see a small detail, internally IV creates a 160 MP bitmap (approx. 458 MB of memory wasted supposing a 24bpp image). I think that this was done to let the user navigate in the zoomed image without having the application to apply the resampling algorithm at each screen refresh, but with the large images used nowadays the bottleneck is no longer the CPU time used to resample the portion of the image to display at each screen refresh, but the memory used to store the resampled image.

[Mij]

Thanks, MItaly. I guessed that is how it worked. Why I called it an inefficient method. What is really annoying is that the resampling operation cannot be aborted. On my very old laptop with a 266MHz Pentium and Win2000, there is no way of breaking out if you accidentally start a big resample. Not even Task manager could stop it. You either have to wait perhaps half an hour for it to complete or turn the power off.

What caught my attention on this thread was the suggestion that WinXP performed better than Win7 or possibly Vista. I am still trying to figure out though why cwb3016's machine seems to be so much better than mine in Vista. Yes the processor speed is just over twice mine, but I had always understood that multiple cores and 64 bit operating systems offered no speed advantage with Irfanview.

[MItaly]

It should not be related much to the processor, it's almost entirely a matter of memory allocation. So if you have much free physical memory the resampling should be much faster, otherwise the system will have to swap the memory pages to disk, and this will likely happen twice (one when writing the resampled image, one when reading it to display it). This method is very inefficient, and because of it most of the image viewers (even the one included with Windows) outperform IV in displaying images with resampling.

[derniwi]

Hi,

I also run Windows 7 x64 on my PC and I have the same problem. Very slow zooming, regardless if the resample is enabled or disabled. Every step I zoom in IrfanView is getting slower. And it does not matter if I select a region and zoom in or if I use the "+" key for zooming.

I tried the following things:
- bind IrfanView to only one CPU (set the affinity to CPU 0 in the task manager)
- test all three zoom calculation methods
- run IV in XP SP3 compatiblity mode

The zooming is still very slow if the zoom value if greater than 100%.

BTW: color management is disabled.

I'm running IrfanView 4.25 with the actual plugins, My PC has 4GB of RAM and enough free...

Regards, Nils.

[Skippybox]

You have to remember that normal window mode is different than full screen mode. Each are independently configured. It can be confusing that not all the options are in Properties.

I suspect that you disabled only the full screen resample options and not the ones in the menu. Disable the new default setting, View>Display options (window mode)>Use "Resample" for zooming. You should now get a zoomed selection to resize as before. Note that now you won't have a resample when you use + or - either. If you now happen to want the resultant resized image to be resampled, then do a refresh by pressing F5. You should not have to disable the Use "Resample" for fitting since it works pretty quick for initial viewing, and will allow you a resample when using F5. So, you may want to re-enable that for full screen.

***

While different systems will ultimately determine performance, I think the confusion here may be a combination of two things:

1. Users have become unaware that there have been two places for resample settings, and only have realized it now that zoom has been made more consistent throughout the program.

2. There have been "update releases" to the original 4.25 executable. This reason is probably why users see very different results. If you are using the original 4.25 from the IrfanView website, then zooming is likely slower than you are used to, but no slower than how it was in prior versions. The reason is that the default settings may not be what you want. Another reason is that there were some bugs in that release in regards to zoom.

One bug was that window mode's resampled zooming had been doing resampled fitting. It also was resampling zoomed selections if resampled zooming was enabled, which was particularly unwanted (although someone seemed to appreciate that bug).

In any case, those issues were resolved in June, and I posted an updated version here. Now zoomed selections remained unresampled unless you press F5 or U (View>Refresh) which will resample the image if you have View>Display options (window mode)>Use "Resample" for fitting enabled. This is the method that was originally discussed at length starting in this post, which proves to be a much better choice. Now you can keep both resample options enabled in the View menu without worrying about a zoomed selection being resampled.

Zoom still can be a little strange in certain instances, but most things have been corrected. Sadly, zoom, as it has always been, is still dreadfully slow because no improvement to the zoom technology has been implemented, like in other fast-zoom programs.

BTW, on my 256MB RAM AMD Athlon4 XP machine, the 100x100 zoom-to-selection on a 1439x1079 image takes a fraction of a second, with both Resample options checked in the View menu. When I press F5 for the actual resample operation (updated version), it takes 39 seconds, which is the same time on the original 4.25 version, for a resampled zoom-to-selection that requires no refresh.

[derniwi]

Hi Skippybox,

that was the problem: I disabled the resampling in the options, but not in the menu
View>Display options (window mode)>Use "Resample" for fitting

That solved the slowing down.

Thansk, Nils.