Reported Histogram of grayscale .png image incorrect

[ableau@genetec.com]

IrfanView for Windows 10 version 4.42- 64 bit

When a grayscale .png image with white saturation is opened, such as attached image "00017 - LPR.png", its histogram is displayed incorrectly for gray values 128-255, although the display is correct for gray values 0-127.

Histogram in Irfan View (incorrect) : see attached file "Histogram IrfanView.png"
Histogram in GIMP (correct): see attached file "Histogram GIMP.png"

[Bhikkhu Pesala]

Which version of IrfanView are you using? Please fill in your forum profile.

My results with your image look different.

[ableau@genetec.com]

Which version of IrfanView are you using? Please fill in your forum profile.

My results with your image look different.

I thought it was clear in my original message: IrfanView for Windows 10 version 4.42- 64 bit

[Bhikkhu Pesala]

Why do I get different results to you in both 32-bit and 64-bit?

[ableau@genetec.com]

More info on how to reproduce the bug

I have attached a second, similar image: "00016 - LPR.png"; upload-it and put it in the same directory as "00017 - LPR.png".
Open "00016 - LPR.png" with IrfanView 4.42
Display the histogram by pressing Shift-H ; histogram shows correctly.
Close histogram window.
Use the right-arrow of the toolbar to switch to "00017 - LPR.png".
Display the histogram by pressing Shift-H ; histogram shows incorrectly.
Close histogram window.
Use the left-arrow of the toolbar to switch-back to "00016 - LPR.png".
Display the histogram by pressing Shift-H ; histogram shows incorrectly now.

Seems to me that the right part of the histogram, for graylevels 128-255, is not cleared when a new image is loaded, so it contains an accumulation of counts from previous images.

[Bhikkhu Pesala]

Still unable to reproduce the issue here, using the 64-bit version.

Maybe someone else can.