Still wrong DPI resolution for PNG export

[Bent U.]

If you export an image with 96 DPI as PNG, the PNG file has a wrong resolution, namely 96.01 DPI. This makes all my images unusable because I am a software developer and use the images in my software to display them in the GUI. I am dependent on the correct resolution. As long as the error is not fixed, I have to correct the resolution in a different program every time afterwards. This is very annoying.

[MEB]

Hi @Bent U.,
Welcome to Affinity Forums
Where are you seeing these dpi values (in what app)? Do you mind attaching a simplified afdesign file from which the exported PNG fails to have proper dpi values please? Thanks.

[Jowday]

2 hours ago, MEB said:

Hi @Bent U.,
Welcome to Affinity Forums
Where are you seeing these dpi values (in what app)? Do you mind attaching a simplified afdesign file from which the exported PNG fails to have proper dpi values please? Thanks.

I could not get anything else out of Designer than 96.0 in metadata.

@MEBWhen I export selection with/without background metadata is not exported even though checked in export settings. Bug?

[Bent U.]

Hi MEB,
thanks for your reply. I have attached a sample file. Paint.net is the program I use to correct the resolution (CTRL+R - Resize). There you can also see the wrong resolution of 96,01 DPI. As I said I use my images to build them into my own software and in Microsoft Visual Studio I can also see the wrong resolution when I use the debugger.
Unfortunately IrfanView does not help in this case, because it only shows the resolution as integers (horizontal and vertical).

Sample_96_DPI.afdesign

[Move Along People]

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[walt.farrell]

Exiftool also reports an exported PNG as 96.0.

@Bent U.: Could you give us the corresponding exported PNG file, too, please?

[Joachim_L]

When I export a PNG from AD having 96.2 dpi and open it in PS I get 96.19 dpi.

[Move Along People]

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[Joachim_L]

[Bent U.]

16 minutes ago, walt.farrell said:

Exiftool also reports an exported PNG as 96.0.

@Bent U.: Could you give us the corresponding exported PNG file, too, please?

I would like to believe that paint.net is wrong, but the fact is that I can set 96 DPI in paint.net, and then the images are displayed correctly in my software.

[Move Along People]

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[walt.farrell]

@Bent U.: Please zip the png file before uploading. (Sorry, I should have mentioned that before. The forum software massages the formats that it supports (PNG, JPG) and can change them, as (I believe) it has when you just posted your .png file.)

[Move Along People]

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[Joachim_L]

1 minute ago, haakoo said:

I meant the real exported png not the outcome from ps

Oh dear, I mixed this discussion up with someone who wanted to export with 96.2 dpi. Nevertheless, when I export 96 dpi document from AD I get 96.0 dpi in xnviewmp and 96.012 dpi in PS. Sorry for the confusion.

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[Bent U.]

1 minute ago, walt.farrell said:

@Bent U.: Please zip the png file before uploading. (Sorry, I should have mentioned that before. The forum software massages the formats that it supports (PNG, JPG) and can change them, as (I believe) it has when you just posted your .png file.)

 

Sample_96_DPI.zip

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[walt.farrell]

4 minutes ago, haakoo said:

It's an afdesign file @walt.farrell so no (I think) conversion by forum software

I asked for (and Brent provided) the .png file just before I asked for the .zip.

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[walt.farrell]

11 minutes ago, haakoo said:

But you rightfully pointed out that forum software may alter common image formats which should not be happening with the already provided afdesign file which contained the original png file which also does show the same results when viewed with xnviewmp

No, the .afdesign file can be Exported into a png, but it does not contain the png file. And even if it did, Brent's complaint is about how it was exported, so we need to see the actual exported file.

[Jowday]

I got the DPI from the metadata in the file read in A file Viewer. Maybe some binary data in the file are different,

[Bent U.]

Okay, I got it. The resolution in PNG files is always stored in pixels per meter, as an integer. 96 DPI corresponds to 3779.5275590551181102362204724409 dots per meter. Affinity Designer saves this as 3780, and paint.net saves 3779.

[Jowday]

1 hour ago, Bent U. said:

 

Sample_96_DPI.zip 2.04 kB · 6 downloads

<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="XMP Core 5.5.0">
 <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <rdf:Description rdf:about=""
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:exif="http://ns.adobe.com/exif/1.0/"
    xmlns:tiff="http://ns.adobe.com/tiff/1.0/"
    xmlns:photoshop="http://ns.adobe.com/photoshop/1.0/"
    xmlns:xmp="http://ns.adobe.com/xap/1.0/"
    xmlns:xmpMM="http://ns.adobe.com/xap/1.0/mm/"
    xmlns:stEvt="http://ns.adobe.com/xap/1.0/sType/ResourceEvent#"
   exif:PixelXDimension="80"
   exif:PixelYDimension="22"
   exif:ColorSpace="1"
   tiff:ImageWidth="80"
   tiff:ImageLength="22"
   tiff:ResolutionUnit="2"
   tiff:XResolution="96.0"
   tiff:YResolution="96.0"
   photoshop:ColorMode="3"
   photoshop:ICCProfile="sRGB IEC61966-2.1"
   xmp:ModifyDate="2020-10-07T12:35:36+02:00"
   xmp:MetadataDate="2020-10-07T12:35:36+02:00">
   <dc:title>
    <rdf:Alt>
     <rdf:li xml:lang="x-default">Sample_96_DPI</rdf:li>
    </rdf:Alt>
   </dc:title>
   <xmpMM:History>
    <rdf:Seq>
     <rdf:li
      stEvt:action="produced"
      stEvt:softwareAgent="Affinity Designer 1.8.5"
      stEvt:when="2020-10-07T12:35:36+02:00"/>
    </rdf:Seq>
   </xmpMM:History>
  </rdf:Description>
 </rdf:RDF>
</x:xmpmeta>

 

[Bent U.]

Affinity Designer obviously supports 3 decimal places. If I set 95.987 DPI, I get what I need, which is 3779 pixels per meter. Perfect!
Thank you all for your efforts.

[walt.farrell]

1 hour ago, Bent U. said:

Okay, I got it. The resolution in PNG files is always stored in pixels per meter, as an integer. 96 DPI corresponds to 3779.5275590551181102362204724409 dots per meter. Affinity Designer saves this as 3780, and paint.net saves 3779.

Interesting. That may help explain one set of numbers that I got which puzzled me, but which I had not yet investigated. PaintShop Pro reported: