30+ FPS GIF

I can’t seem to figure out how to read/write 30+ FP GIF’s with the “GIF-FI” format.

If I do: imageio.mimwrite("test.gif", images, format="GIF-FI", fps=29)

Followed by: frame_duration_ms = imageio.get_reader("test.gif", format="GIF-FI").get_next_data().meta.ANIMATION.FrameTime

Then frame_duration_ms is 30, but I expect it to be 34 (1000 / 29 == 34.4).

I’ve done some data collection, and writing/reading generally comes out correct…sometimes:

• write 1 / read 1
• write 10 / read 10
• write 15 / read 16.666666
• write 25 / read 25
• write 30 / read 33.333333
• write 40 / read 50
• write 50 / read 50
• write 60 / read 100
• write 100 / read 100

The in -> out is an odd pattern… it seems like there’s an inappropriate truncation/division happening somewhere?

I’ve poked around the codebase a bit, and as far as imageio/plugins/_freeimage.py(759)set_meta_data(), the frametime is correct:

> /Users/joe/repos/third-party/imageio/imageio/plugins/_freeimage.py(759)set_meta_data()
    758                         # Set properties
--> 759                         import ipdb; ipdb.set_trace()  # XXX BREAKPOINT
    760                         lib.FreeImage_SetTagKey(tag, tag_name.encode('utf-8'))

ipdb> tag_name
'FrameTime'
ipdb> tag_val
array([34], dtype=uint32)
ipdb>

At the point the bytes are read from lib.FreeImage, the value is already wrong:

> /Users/joe/repos/third-party/imageio/imageio/plugins/_freeimage.py(692)get_meta_data()
    691                         import ipdb; ipdb.set_trace()  # XXX BREAKPOINT
--> 692                         subdict = metadata.setdefault(model_name, Dict())
    693                         subdict[tag_name] = tag_val

ipdb> tag_val
30
ipdb>

Am I doing something wrong, or is there a bug in the GIF reading/writing code?

Using:

• imageio: v0.5.1-658-g5d323c0 from this repo
• FreeImage: 3.17.0 from brew
• OS: OSX 10.11.6

[toejough]

also, this module is sweet - thank you for building it and making it available!

[almarklein]

Hehe, after looking into what’s wrong with both the Pillow and FI animated gif modules, I found that its a limitation of GIF itself; the “delay time”, in GIF’s terminology is expressed in hundredths of seconds. See e.g. https://en.wikipedia.org/wiki/GIF (search for “delay”), or https://github.com/imageio/imageio/blob/master/imageio/plugins/pillowmulti.py#L288.

I will add a note to the docs 😃