Pre Flight Check (Publisher 2.2., macOS) Questionable Error

[Bluehen]

The Pre Flight Check for images is set for 300 Dpi. After running the PFC, many images are reported as errors with 299 Dpi. However, all these images are confirmed as 300 Dpi.

Interestingly, the images showing as errors are all placed in "Landscape" picture frames. None of the other images placed in "Portait" frames are showing errors.  

Is this a bug?

[Old Bruce]

Could well be the landscape frames are stretching the images just enough so they become ever so sightly less than 300 dpi and are reported as 299 in the preflight whereas the method you used to "confirm" their dpi is showing 300 for some reason. What is the way you confirmed the dpi?

[walt.farrell]

2 minutes ago, Bluehen said:

However, all these images are confirmed as 300 Dpi.

Confirmed how?

3 minutes ago, Bluehen said:

Is this a bug?

Can you provide a sample .afpub document that shows this happening?

[Bluehen]

The image size was confirmed by checking the actual file size; all images are the same size, 2100x1680.

 

[walt.farrell]

1 minute ago, Bluehen said:

The image size was confirmed by checking the actual file size; all images are the same size, 2100x1680.

 

But do all the Picture Frames have the same scaling Properties?

What does the Context Toolbar show for each, and what does the Resource Manager show?

[Bluehen]

The entire document is quite large. Is there a method to extract a portion in .afpub format?

[Bluehen]

Scaling for all  frames is set to "None."

Resource Manager is showing the images in question as 299 Dpi 

[walt.farrell]

13 minutes ago, Bluehen said:

The entire document is quite large. Is there a method to extract a portion in .afpub format?

You could create a new document, and in that document use Document > Add Pages from File... and select a small range of pages.

Or you could try creating a new document and simply adding the Picture Frames the same way you did in the original, and Placing some sample images. If the same issue occurs, you have your sample. Make sure they are Embedded, not Linked, Save it, and we can use that .afpub as the demonstration.

[MikeTO]

It's probably a minor rounding error when using inches as the measurement units. I'd just set the preflight warning to 299 and not worry about it.

But I can test it for you if you copy one of the picture frames to a blank document - I don't need the picture in the frame.

Cheers

[Bluehen]

Trying to upload 3.4 Mb file, but not finishing for some reason. Ill keep trying.

 

[Bluehen]

Two sample pages with problem images.

 

Edited September 29, 2023 by Bluehen
Problem resolved

[Bluehen]

Hope this is a "rounding error." Odd that the erroe only occurs for images placed in Landscape picture frame. Similar sized images in Portait frame are okay.

 

[Old Bruce]

Even though the images weren't included this is what I am seeing.

 

[walt.farrell]

I see:

[Bluehen]

Okay, I'm confused. The image at 2100x1680 at 300 Dpi is equivalent to the Picture Frame at 7 in x 5.6 in. 

How can it be 299 Dpi?

 

[MikeTO]

If I open your document to page 1 and place a 2100x1680 72dpi test image into the frame I get 299dpi. If I go to the master page and place it to the actual frame I get 300dpi.

If I open your document again and copy the master frame to a regular page and place the test image into it I get 300dpi instead of the 299 when I place it into the master layer frame. Obviously these should all be the same.

This is just a rounding error. You wouldn't normally notice it except it's your preflight threshold. I had it happen this week with Preflight's bleed hazard - the object was outside the safe zone but the value was being rounded and didn't trigger the error.

The best solution is just to change your preflight threshold to 299.

[Bluehen]

Thanks for the help. I’ll proceed on with the images as placed. 
For my understabding, the rounding error occurs within Publisher?

[MikeTO]

35 minutes ago, Bluehen said:

Thanks for the help. I’ll proceed on with the images as placed. 
For my understabding, the rounding error occurs within Publisher?

Yes, you're not doing anything wrong, that's why I suggested tweaking the preflight threshold so it doesn't give you false alerts.

[Oufti]

5 hours ago, Bluehen said:

Okay, I'm confused. The image at 2100x1680 at 300 Dpi is equivalent to the Picture Frame at 7 in x 5.6 in. 

How can it be 299 Dpi?

For example, it could happen if you convert a pixel size in points (= 1/72 inch), round it to entire point value, then convert back to pixels and round again. 

Like this: 

— Note that this rounding error doesn't happen with the other dimension, since 2100 is a multiple of 3(00), so you have a round number of points (504). 

This minuscule error (85µ, one or two hair) is possibly triggered by a position exact in pixels but not in points, or the reverse… 

[Bluehen]

Thanks for the concise explanation. I'm still puzzled as to why this is only happening with images placed in the Landscape frame. The same image in the Portrait orientation does not result in the 299 Dpi "error." Perhaps a software quirk?

[Oufti]

5 hours ago, Bluehen said:

I'm still puzzled as to why this is only happening with images placed in the Landscape frame.

As one of the dimension is an exact count both in pixels and points but the other not, I guess it could be related to sub-decimal position + sub-decimal dimension cumulated, inducing rounding or not, but it's so tiny…  

[Bluehen]

Thanks again for the great analysis.