Can a PNG image contain multiple pages?

Question

On OSX I converted a multi-page PDF file to PNG and (somehow) it created a multi-page PNG file.

Is there an extension to the PNG format that allows this? Or is this not something I can validly create?

~~~~

To clarify, this is a PNG file, per the builtin file command and the identify command from imagemagick.

$ file algorithms-combined-print.png 
algorithms-combined-print.png: PNG image data, 1275 x 1650, 8-bit/color RGBA, non-interlaced

$ identify algorithms-combined-print.png 
algorithms-combined-print.png PNG 1275x1650 1275x1650+0+0 8-bit sRGB 3.537MB 0.000u 0:00.000

And here is a pastebin of the command identify -verbose algorithms-combined-print.png: http://pastebin.com/hw1yuRKa

What is notable from that output is that the pixel count is Number pixels: 2.104M which corresponds to one page. However, the file size is 3.537MB, which is clearly sufficient to hold all the pages.

Per request, here is the output of pngcheck: http://pastebin.com/aCRMEd9L

Run "pngcheck -v algo-stroke.png" and show us the result. You can get pngcheck from http://www.libpng.org/pub/png/apps/pngcheck.html — Glenn Randers-Pehrson, Dec 31 '15 at 22:34
@GlennRanders-Pehrson thanks for the advice, pastebin attached — William Entriken, Jan 02 '16 at 08:34
Also, this is reproducible, so anyone with a Mac can try this at home. — William Entriken, Jan 02 '16 at 08:35
You have `aCTL` and `fCTL` in the output of `pngcheck` - these are signs of APNG... http://stackoverflow.com/a/33432942/2836621 — Mark Setchell, Jan 02 '16 at 09:18

score 18 · Accepted Answer · edited May 06 '21 at 10:51

18

PNG does not support "multipage" images.

MNG is a PNG variant that supports multiple images - mostly for animations, but it's not a real PNG image (diffent signature/header), and has never become popular.

APNG is a similar attempt, but more focused on animations - it's more popular and alive, though it's less official - it's also PNG compatible (a standard PNG viewer, unaware of APNG, will display it as a single PNG image).

Another possible explanation is that your image is actually a TIFF image with a wrong .png extension, and the viewer ignores it.

The only way to know for sure is to look inside the image file itself (at least to the first bytes)

Update: given the pngcheck output, it seems to be a APNG file.

edited May 06 '21 at 10:51

David Jones

4,766
3
32
45

answered Jan 01 '16 at 12:33

leonbloy

73,180
20
142
190

thanks for the reply, I have updated the post to show `file`, `imagemagick` and `pngcheck` all attesting that this is a PNG file. – William Entriken Jan 02 '16 at 08:35
3

APNG was designed to be able to hide inside a regular PNG. Applications such as ImageMagick that don't recognize APNG chunks will handle it as a regular single-image PNG and only show you the base image. – Glenn Randers-Pehrson Jan 02 '16 at 13:11
also it can be valid GIF – Vladimir Apr 04 '23 at 13:45

Can a PNG image contain multiple pages?

1 Answers1

Linked