Export PNG Image: Pixel - DPI

[merbali]

Hello,

There is a small inconsistency with the display and conversion of Pixel and DPI at "Export PNG Image". Both in Inkscape 0485 and in 0921.

When DPI is raised, pixels are also increased.
As pixels increase, so does DPI.
From the point of first right, but not really.

I have a graphic image with 3000x3000 pixels (rectangle). With 300 dpi in print, this is 25.4x25.4 cm. I open "Export PNG Image" and select "Selection", then at "Bitmap Size / Image Size" pixels "3000" and DPI "92" are displayed. If I change the dpi now to "300", then the pixels rise to "9375" and that's not right. Here you do not have to change the pixel number, but the print resolution in cm or inch. Pixel and DPI are just two values ​​needed to calculate the print resolution. Both are independent of each other, but together they affect the print resolution. So it's wrong to make each other dependent on each other by the DPI changing the pixels or the pixels changing the DPI. This is wrong and in no way correct. It would be better if the value of the print resolution were displayed and calculated over the Pixel and DPI values.

Pixel | DPI | Print resolution in cm
3000x3000 | 600 | 12,7x12,7
3000x3000 | 300 | 25,4x25,4
3000x3000 | 200 | 38,1x38,1
3000x3000 | 100 | 76,2x76,2

This can be tested very easily with IrfanView via the Image "Information" (Image properties).

[Moini]

px and screen pixels are not the same. A px in Inkscape (as well as in CSS) is defined as 1/96th of an inch. The dialog is working correctly.
You need to resize your image to get different values.

[Moini]

To know more, read the unit series, post I to IV by Marc Jeanmougain, a principal Inkscape developer:
https://www.patreon.com/posts/units-part-i-13563546

[brynn]

I could be saying something that's not precisely correct, since I struggle with dpi/resolution issues.  But the Export PNG dialog is just for exporting into the PNG format.  It has nothing to do with printing.  Whenever you're ready to print the image, then you can set the proper size that you need.  Or if the image it going onto a webpage, you can set the size for the image in the html.

(Also, note that Inkscape is not strong with printing.  A lot of people either save as PDF and use PDF software to print, or else Print to PDF, if they need anything more than very basic print features.)