Zoom bugs

[Philbert]

I assume these are bugs, not just user error, since I'm using IV the same way I have been for the past 6 or 7 years. In 4.20 the zoom doesn't go to 100% like it used to it goes to other numbers similar to that like 98, 103, 112, but I can't get 100%. Also if I am zoomed in and pan to one part of the image sometimes adjusting the zoom causes it to jump to the center, sometimes it doesn't. I made a video but my mic isn't very good (actually an old pair of headphones) so you may have to turn your volume up:

http://screencast.com/t/TdvlsZLJ

Vista Ultimate x64, IrfanView 4.20
Core 2 Quad 2.4 GHz, GeForce 8800 GTS, 4GB RAM

[j7n]

Go to Preferences -> Viewing and select fixed values as the zoom method. This should ensure that 100% is accessible by pressing "+" and "-". I've got no solution for the viewport-jumping-to-center issue. This bug was present before the zoom got revamped in v4.10 and is not related to it.

In v4.20 zooming was fixed so that it always returns to the starting value. I think you might have chosen to fit images to window or to desktop, in which case the zoom was never 1:1 to start with. IV will guarantee that you will always be able to return to whatever the zoom level is required to display full image. In your case 35%.

[Philbert]

Wow well I get 100% now, but anything that goes over 100% causes the zoom to get sluggish, it's takes twice as long each time I click + or -. Thanks. I somehow missed the 4.10 update so I'm coming from 4.0

[j7n]

That setting only changes the magnification scale, so there sholdn't be any speed penalty. Zooming will be slow if you have selected "Use resample for fitting". The program is not clever enough to resample only the viewport and will process the entire picture.

The release of v4.10 caused great dissatisfaction because of changed zoom scale. It became completely impossible to zoom to 25, 50 and 100 percent. You should be glad that you missed that version.

[Philbert]

Are you referring to "Use 'Resample' fuction for display options" under the Fullscreen tab? I didn't check it, but it's checked. Of course I'm not using it in fullscreen mode anyway.

[j7n]

That one is for fullscreen. Windowed mode is configured in

Menu -> View -> Display options

[Philbert]

Oh OK, thanks, I think I'll leave that off, but it's good to know that it's there.

[Skippybox]

In v4.20 zooming was fixed so that it always returns to the starting value.

Not so much. See Zoom Bug Continued!

[j7n]

The old zoom was not fully returned. However, the new relative zoom (which is better) now works properly.

[Skippybox]

That's true. Relative works well now, but it's absolute that doesn't. Reread my thread again and see!

[Skippybox]

Did you understand it j7n? Perhaps I was unclear in my thread. Do you need me to clarify what is wrong with the absolute zoom?

[j7n]

I understood your report and already expressed my opinion that old zoom should have been left alone. If someone needs fixed 25% step, he could choose the old zoom. There was no need to 'relativize' it when the proper "fixed values" magnification method exists.

I did not get how the functionality of relative zooming has diminished in version 4.20. IMHO, this method has no advantages compared to "fixed values". Although the step of 100% is now ensured (or rather 100% of the starting zoom), I still cannot get to 25, 50, 200 percent with it.

[Skippybox]

Regardless of what we had before, we now have these three zoom options, which we must work with in v4.20. They are all fine. One can use fixed values and it will be fairly good under most situations. The old zoom worked like absolute step. But it doesn't matter if you need 25%. Many steps will encounter the situation I am referring to in absolute zoom. The absolute zoom only works down to the step itself. So after that, the zoom pattern gets destroyed by relativeness. Thus zooming in won't get you back to your starting point. Don't you think it shouldn't do this?

[Skippybox]

I did not get how the functionality of relative zooming has diminished in version 4.20. IMHO, this method has no advantages compared to "fixed values". Although the step of 100% is now ensured (or rather 100% of the starting zoom), I still cannot get to 25, 50, 200 percent with it.

Relative step is not meant to replace absolute step or fixed values. Each choice is for a different purpose. I don't usually use relative step, but it must be important if Irfan included in two versions, despite all the fuss. I can see how it could be useful in some situations. The new relative step zoom option definitely needed to be made so you could return to a starting point. My point about relative zooming being diminished, is that when it was improved to allow a user to return to his starting point, the calculation failed to be relative. Basically, the way Irfan implemented the new design makes relative zooming out from a starting point inaccurate. The step is not true, going in one direction versus the other.

If someone wanted a 10% relative step starting at 100% you would expect to zoom in to values like 110, 121, 133, 146, etc. and zooming out 90, 81, 73, 66, etc, which would be 10% more and 10% less, respectively. Instead, zooming out uses a step of ~9.1% because the reciprocal of 1.10 is 0.91, which makes the calculation simpler. So you get zooming out values of 91, 83, 75, 68, etc. So, it's 10% more zooming in, but 9.1% less zooming out. Not consistent.

I think the algorithm needs changing. One could workaround this by modifying the percentage when zooming out, but that is inaccurate and tedious. It should be quite easy to adjust the formula in the program. The starting zoom just needs to be saved, so it is known whether the zoom should be, for instance multiplied or divided by 0.9 OR multiplied or divided by 1.1. Currently, it just multiplies or divides by 1.1, which is inaccurate.

[Skippybox]

The old zoom was not fully returned.

Maybe I interpreted you wrong. Did you mean that in 4.2 the old zoom (which is now called absolute step) was not fully returned to its prior functionality? And that the relative calculation applied to it after reaching the zoom step, is its problem?