ZZTop

As this file is software screen, I think both entries 72 and 96 are wrong and correct size is displayed on device screen that is used to show this image - based on resolution of that screen. So in my opinion only correct thing for any image editor would be to follow source file metadata structure and not write anything new there related to image resolution.

I have looked into this and Rick is absolutely right. So here is metadata shown by TweakPNG (freeware PNG metadata viewer): http://entropymine.com/jason/tweakpng/ And here is the metadata os same image when saved in Paint.net: Now this file would display 96 DPI in whichever program it is opened with, but if we delete metadata values, than say Photoshop would display same file with resolution of 72.

That could be it, when I open file in regular Windows paint and make "save as" backup copy it changes resolution to 96, but than again way that is not happening when you save file within Paint.net to resolution of 72? It has to be some incompatibility with that png type.

Yes when saved as 72 dpi in Paint.net than it reopens file normally as 72 dpi. I didnt want to speak about it before we understand the problem in order not to make bigger confusion. So this issue is only occurring with at least one type of png file, while other programs open that file normally.

You dont understand core of the problem. (please do excuse me Im not trying to be rude, EN is not my native language - I dont know how to express that sentence without being rude, but be sure that I dont have that intention) Problem is happening to files that ware created outside of Paint.net. In test image, I provided in zip file, in my first post - you can observe bug happening. -First open native file in PS or Gimp and see resolution - 72 -Than open in Paint.net and check there - 96 -Than save image in Paint.net without resizing it or doing anything - just "save as" a backup png copy -finally open copy in PS/Gimp and copy resolution would be 96 From observation above - you can see that PS is displaying true resolution of native file whichever it may be 72 or 96, but Paint.net is changing resolution of native file to 96 without any notice. I dont know in which program that png file is created. It may be Paint.net issue only with that kind of PNG, but it is still an issue, since PS or other programs dont do that automatic change of native file. I hope that issue is now more clear.

Wrong is that Paint.net changes image printing size - If I open image in program and use save as -> PNG to different location and than open that image in Photoshop, than that image would have 96 DPI in Photoshop as well. I understand that there is no quality loss in what Paint.net is doing - it makes higher pixel density with image shrink. But point is that program is making an undesirable and uncontrolled change to file with no apparent reason.

Greetings, thanks for replays - however it seems to me that we dont understand eachother so I will provide you with screenshots and file to test. So here it is: On screenshot 1, you can see just opened image in paint.net (on this machine is old version, but its same with new one). On second image you can see same image just opened in Adobe Photoshop CS6 - tested also on CC2015 at work and it is same. I have also uploaded test PNG to zip file so you can test it yourself. (edit I just re-uploaded images, so now units are same in both programs.) Test picture.zip

Ok, so lets say I have PNG file that is 17x17cm with resolution of 72 dpi, when I open it in Paint.net (latest version), it automatically changes its size so it becomes shrink say 9x9 cm (not exact value - just example) and resolution becomes 96 dpi. So for some reason Paint.net is doing an automatic size change of PNG file. Is this an "feature" or there is problem with program behavior?