why my dimension and color format changing after i save on png

[T-Bali]

why did my dimension and color format change after I saved it on PNG in Affinity Designer 2? I saved my file (Document Setup) with dimensions 22x240 inches and color format on CMYK. After I saved and exported, my file changed to 10x110 inches, and the color format back to RGB

[Hangman]

Hi @T-Bali and welcome to the forums,

The PNG file format doesn't support CMYK so you'd be better off using either JPG or TIFF.

With regards to the exported size, despite there being no technical limit to the dimensions of a PNG file, unlike JPEG files which have a maximum width and height of 65,535 pixels, different software may apply restrictions for practical reasons such as memory.

It appears as though Affinity apps apply a maximum width and height of 32,767 pixels (half that for JPEG files) which seems a little odd but explains why your exported file is only 10 x 109.2 inches when exported...

A 300 dpi document of 22 x 240 inches is 6,600 px x 72,000 px

With the Restriction Applied by Affinity Apps

32,767 / 72,000 = 45.5% therefore

22" x 45.5% = 10" and 240" x 45.5% = 109.2"

[NotMyFault]

13 minutes ago, Hangman said:

It appears as though Affinity apps apply a maximum width and height of 32,767 pixels (half that for JPEG files) which seems a little odd but explains why your exported file is only 10 x 109.2 inches when exported...

This is due to Affinity using an old Window GDI API having this limit.

i don't understand why affinity never used a different export routine, especially on non-windows platforms.

 

[Hangman]

39 minutes ago, NotMyFault said:

This is due to Affinity using an old Window GDI API having this limit.

i don't understand why affinity never used a different export routine, especially on non-windows platforms.

Interesting, thanks for the link... I'm somewhat surprised as well since this is, as far as I can tell, a Windows 32-bit limitation. I think my expectation would be, certainly on macOS that the limitation wouldn't apply...

[R C-R]

8 hours ago, Hangman said:

A 300 dpi document of 22 x 240 inches is 6,600 px x 72,000 px

With the Restriction Applied by Affinity Apps

32,767 / 72,000 = 45.5% therefore

22" x 45.5% = 10" and 240" x 45.5% = 109.2"

On my Mac, I don't even get proportional reduced scaling so for instance, if I try  6,600 px x 72,000 px on one of my 1920x1280 single layer jpeg files opened in AP, I get a very distorted 3003 × 32767 px png. The export takes about 10 seconds to complete, & the progress bar does not appear until it is almost complete.

Also, it seems hit or miss if I get the warning message or not.

So it seems very buggy as well as being an unnecessary & arbitrary restriction.

[Hangman]

35 minutes ago, R C-R said:

…if I try 6,600 px x 72,000 px on one of my 1920x1280 single layer jpeg files opened in AP, I get a very distorted 3003 × 32767 px png.

I’m not sure I follow in as much as 1,920 x 1,280 doesn’t have the same aspect ratio as 6,600 x 72,000 but…

• 6,600 px x 45.5% = 3,003 px
• 72,000 px x 45.5% = 32,767 px

Note: The actual percentage is closer to 45.50972222222222%

I’ve not tested in detail but I certainly see the warning message when exporting a 22 x 240 inch, 300 dpi file to PNG in both v1 and v2.