Reported Can't zoom in at 0% zoom

[ET3D]

Take a 2000x1 image, it's scaled down when opened and shows as 0% zoom. It can't be zoomed in. ("Original Size" does work.)

[Bhikkhu Pesala]

Unable to reproduce here. Which version of IrfanView are you using, and what are you Zoom settings?

[Mij]

I can reproduce it when using "fit to window" but decided it was not worth commenting on. If you try to scale a 1 pixel high image to less than 1:1 (100% zoom) then you are asking for it to be shown using less than 1 pixel height on the screen, which is clearly impossible.

Irfanview does in fact show it initially at 1 screen pixel height and displays a figure for zoom ratio but then refuses to change that zoom setting until you request something sensible like 100% (by pressing Ctrl+H). After that you can increase the zoom ratio setting above 100% but cannot reduce it below that. All a reasonable response by Irfanview IMHO to a fairly silly request made upon it.

[Bhikkhu Pesala]

The OP said, “Cannot be zoomed in,” which I take to mean that one cannot enlarge the view, not reduce it, which I didn't even try to do.

[Mij]

In fact if you do what I assume the OP is doing you cannot zoom either in or out.

In the first attached image the thin 4 colour line is a 2000x1 pixel image as you can see in the status line at the bottom. It has been opened in a 500 pixel wide window with "Fit images to Window" selected in the Display options. The zoom ratio is shown in the status line as 25% which is what it should be. The caption bar at the top claims that the image size has been zoomed to 500x0 pixels which is again what it should be, but if it were really 0 pixels high you would not see it at all. It is actually displayed on screen 1 pixel high so that you can see something. If you try to change the zoom ratio either up or down using Ctrl with +, - or scrollwheel, you hear an error beep and the zoom stays the same.
I can change the zoom ratio by stretching the window. The line is continually refitted and the zoomed width reading tracks the width of the window, but the height remains shown as 0 until the window reaches 1000 pixels wide. The height then shows as 1 pixel, what it actually is, and the zoom ratio is 50% (second image). I still cannot zoom either in or out using any of the Ctrl combination shortcuts above though.
I have to press Ctrl+H to go to 100% zoom before I can start using Ctrl and + to increase zoom ratio

On experimenting I see that it is not possible to reduce zoomed size of a displayed image below 2 pixels using the Ctrl shortcuts for any display mode. The only way to display an image 1 pixel high is by opening it at that size and when it is shown as less than 2 high it is not possible to either reduce or increase the size that way at any zoom ratio of less than 100%.

All of which is quite interesting, but is it a bug or just a sensible limitation on minimum image size?

[ET3D]

Irfanview does in fact show it initially at 1 screen pixel height and displays a figure for zoom ratio but then refuses to change that zoom setting until you request something sensible like 100% (by pressing Ctrl+H). After that you can increase the zoom ratio setting above 100% but cannot reduce it below that. All a reasonable response by Irfanview IMHO to a fairly silly request made upon it.

I don't think that putting the user in a place where the program seems unable to respond correctly can be considered reasonable. Sure it's not a huge show stopping bug, but the user didn't do anything out of the ordinary, except choose an image of an unusual aspect ratio, so it should be expected that Irfanview handle that case in a manner which doesn't break any usual interaction (in this case, zooming).