Large resolution png support - possible/not?

[HorribleGoat]

Hello!

Im pretty new Affinity user but so far loving the speed of the program! 

Now my question is regarding very high resolution images and png format as I often work with 40960+ pixel images and png has bee reliable transfer format between different programs the images go to from image editor (previously gimp and various programs that generate image data and now exploring Affinity Photo as part of my workflow) 

Now previously I have had no trouble using 40960+ pixel images with png format but Affinity seems to have png resolution capped at 32762px and Im wondering if this is something that could be looked into in the future and possibly the limits could be revised?

Could not find similar topic from the forum history so wanted to put this out there.

-Goat

[Callum]

Hi Horrible,

This was a design choice so its not something thats likely to change I'm afraid. You may want to take a look at Alfreds posts in the below thread:

Thanks
C

[fde101]

@Callum,

It appears that the same seemingly arbitrary restriction is also being imposed on the Mac version.

This is highly unfortunate, particularly as the message states that PNG limits the resolution to that which is clearly untrue.  PNG uses an unsigned 32-bit value to hold each of width and height, so it can support images over 4.2 million pixels high and wide.

The message should be changed to read something more like "PNG support by this application is limited to images with dimensions no greater than..."

Otherwise you are lying to the user.

[Old Bruce]

3 hours ago, fde101 said:

The message should be changed to read something more like "PNG support by this application is limited to images with dimensions no greater than..."

What message? 

[fde101]

4 hours ago, Old Bruce said:

What message? 

Create a document that is 40000 pixels wide or so and try to export it as a PNG.  In the export window there is a warning message that makes the false claim that the PNG format does not support images with dimensions greater than 32,767 pixels wide.  The PNG format does support dimensions FAR greater than that.

[Old Bruce]

12 hours ago, fde101 said:

Create a document that is 40000 pixels wide or so and try to export it as a PNG.  In the export window there is a warning message that makes the false claim that the PNG format does not support images with dimensions greater than 32,767 pixels wide.  The PNG format does support dimensions FAR greater than that.

I see no message with any claim, that is here on Mac. Must be a windows thing.

For what it is worth there should be a message of some sort because the PNG is truncated to (8^2)-1 pixels instead of the 40,000 or larger.

[walt.farrell]

16 minutes ago, Old Bruce said:

I see no message with any claim, that is here on Mac

Does the Export dialog show the full size of 40000 px? Or is it forced to a max of 32768 as it is in the iPad version of Affinity Photo?

[Old Bruce]

It is scaled to a max size. 

[Old Bruce]

1 hour ago, LondonSquirrel said:

Is that correct? 

From http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html: Under IHDR Image Header, Width and Height: Width and height give the image dimensions in pixels. They are 4-byte integers. Zero is an invalid value. The maximum for each is 231 -1  in order to accommodate languages that have difficulty with unsigned 4-byte values.

So he is off by a multiple of 2 instead of a multiple of 65,000. Two billion is way bigger than 32 thousand.

[fde101]

2 hours ago, LondonSquirrel said:

The maximum for each is 231 -1  in order to accommodate languages that have difficulty with unsigned 4-byte values.

Good catch, I had missed that comment.  Then yes, it is still over 2 million, but not the 4 million I had miscalculated as.  The point still stands.

[fde101]

On 11/30/2021 at 9:44 AM, Old Bruce said:

I see no message with any claim, that is here on Mac. Must be a windows thing.

This is definitely on the Mac:

On 11/30/2021 at 9:44 AM, Old Bruce said:

For what it is worth there should be a message of some sort because the PNG is truncated to (8^2)-1 pixels instead of the 40,000 or larger.

(8^2)-1 = 63, that would be awfully small.  I think what you are looking for is (2^15) - 1.

The issue is that the message claims that the PNG format is limited to that size, but that is not true.  PNG supports up to (2^31) - 1; the limitation is imposed by the application NOT by the file format.

[Medical Officer Bones]

Same in Windows:

It's very inconsistent and, what's more, irrational behaviour in Photo. Photo does open a 1 million px wide PNG image that I saved from PhotoLine, but refuses to resave the same PNG file at its original dimensions. Why allow for the import of higher than 32768px wide PNG files, if the application blocks saving those same files it opens correctly? That makes little sense: on the one hand insisting that PNG files 'officially' only support up to 32768px wide and high bitmaps, but on the other hand still supporting the import of far higher resolution PNG files.

That is very illogical ambiguous software behaviour.

Besides, it seems only Affinity Photo enforces these arbitrary PNG export size limits: all other software that I use supports saving higher resolution PNG files. Krita also saves such PNG files without issues (including the 1 million px wide PNG file), for example. ClipStudio has no qualms exporting a 100.000px wide PNG file. Irfanview imports and exports much larger PNG files.

Photoshop actually limits file format choices for saving a 250.000 pixel file to PSB, TIFF, and PNG - other file formats are excluded, meaning the PS developers chose PNG as one of the few file formats capable of saving such files!

And as @fde101 reiterates: the max width or height is limited to (2^31)-1: 2,147,483,647 . I wonder if the developer implementing PNG export misread the PNG format specs. 😉

[HorribleGoat]

On 11/25/2021 at 3:58 PM, Callum said:

Hi Horrible,

This was a design choice so its not something thats likely to change I'm afraid. You may want to take a look at Alfreds posts in the below thread:

Thanks
C

This is quite unfortunate and to be honest odd design choice and seems like others are wondering on it too.
Anyway, I have other programs I can use for the conversion. Its just odd that I have to rely on such methods as I did purchase Affinity to get rid of more obsolete and less performant tools.

Edited December 3, 2021 by HorribleGoat

[dr_who]

On 12/3/2021 at 7:24 AM, HorribleGoat said:

This is quite unfortunate and to be honest odd design choice and seems like others are wondering on it too.
Anyway, I have other programs I can use for the conversion. Its just odd that I have to rely on such methods as I did purchase Affinity to get rid of more obsolete and less performant tools.

Agreed. I can't wrap my head around what this has to do with "design". I understand that images beyond 32,767px are a pretty niche thing but within the UI/UX realm, you sometimes need very large sprite sheets. As things currently stand, I have to export my sprite sheets as tif files and then have them converted to png files via an online service. Which I find needlessly convoluted.