BytesIO png to surface (cairo.IOError: error while reading from input stream)

[maslaff]

bytes = BytesIO()
# save png to BytesIO from PilImage
img.save(bytes, format='png')
imgsf = cairo.ImageSurface.create_from_png(bytes)

cairo.IOError: error while reading from input stream

Through file normally work. E.g.:

img.save('img.png', format='png')
imgsf = cairo.ImageSurface.create_from_png('img.png')

Ok

[dolfandringa]

I am fetching a png image online in a jupyter notebook and save it to io.BytesIO.
If I display it with in a jupyter notebook with

display(Image(background.getvalue(), width=width))

it shows up just fine, but if I

surface=cairo.ImageSurface.create_from_png(background)

if shows me the same error. For some reason pycairo can not read from any file-like object.

EDIT:
I just noticed, if I open a file with f=open('filename.png', 'w+b') then write and image to it, then f.seek(0) and then pass that file like object to create_from_png, it fails as well with the same error. But passing just the filename to create_from_png works just fine.

[lazka]

You need to seek to where you want to read from first, otherwise pycairo will only find an empty file object:

bytes = BytesIO()
# save png to BytesIO from PilImage
img.save(bytes, format='png')

bytes.seek(0)

imgsf = cairo.ImageSurface.create_from_png(bytes)

[maslaff]

bytes.seek(0)

This is work! Thanks!