Best way to display image from URL in Python3

Ryan_Nelson · March 20, 2015, 12:54am

Hello all,

I’m porting over some code that used Py2.7 urllib2.urlopen(url) to grab some image data from the net and load with pyplot.imread. It doesn’t work quite right in Py3.4. I found a couple of refs:

https://github.com/matplotlib/matplotlib/pull/1650

http://stackoverflow.com/questions/15183170/python-crash-when-downloading-image-as-numpy-array

They suggest io.BytesIO(urllib.request.urlopen(url).read()) as a replacement for Py3. Is this the best practice? Does anyone know a simpler way to do this?

Ryan

Benjamin_Root · March 20, 2015, 1:51pm

According to the PR you reference, the fix for this was merged back in Jan 2013, so that means that this fix is in version 1.2.x and up. Are you saying that you still can’t do imread(urllib.request.urlopen(url))?

···

On Thu, Mar 19, 2015 at 8:54 PM, Ryan Nelson <rnelsonchem@…287…> wrote:

Hello all,

I’m porting over some code that used Py2.7 urllib2.urlopen(url) to grab some image data from the net and load with pyplot.imread. It doesn’t work quite right in Py3.4. I found a couple of refs:

https://github.com/matplotlib/matplotlib/pull/1650

http://stackoverflow.com/questions/15183170/python-crash-when-downloading-image-as-numpy-array

They suggest io.BytesIO(urllib.request.urlopen(url).read()) as a replacement for Py3. Is this the best practice? Does anyone know a simpler way to do this?

Ryan

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Ryan_Nelson · March 20, 2015, 3:48pm

Thanks, Ben. I should have made that more clear. If I run the code from the PR, I get the following error:

Traceback (most recent call last):

File “junk.py”, line 11, in

image = pyplot.imread(data) # crash on py3.x

File “/home/nelson/apps/miniconda/lib/python3.4/site-packages/matplotlib/pyplot.py”, line 2215, in imread

return _imread(*args, **kwargs)

File “/home/nelson/apps/miniconda/lib/python3.4/site-packages/matplotlib/image.py”, line 1270, in imread

return handler(fname)

RuntimeError: _image_module::readpng: file not recognized as a PNG file

My code that I’m trying to port essentially does the same thing, and I get the same error. I ran this example just now from Anaconda Python 3.4 install with MPL 1.4.3.

My impression from the PR was that this should work out of the box now. I figured that maybe that was not quite the case. The implementations between Py2 and 3 are quite different. Figured there must be a different way that I wasn’t aware of.

Ryan

···

On Fri, Mar 20, 2015 at 9:51 AM, Benjamin Root <ben.root@…1304…> wrote:

According to the PR you reference, the fix for this was merged back in Jan 2013, so that means that this fix is in version 1.2.x and up. Are you saying that you still can’t do imread(urllib.request.urlopen(url))?

On Thu, Mar 19, 2015 at 8:54 PM, Ryan Nelson <rnelsonchem@…1896…> wrote:

Hello all,

I’m porting over some code that used Py2.7 urllib2.urlopen(url) to grab some image data from the net and load with pyplot.imread. It doesn’t work quite right in Py3.4. I found a couple of refs:

https://github.com/matplotlib/matplotlib/pull/1650

http://stackoverflow.com/questions/15183170/python-crash-when-downloading-image-as-numpy-array

They suggest io.BytesIO(urllib.request.urlopen(url).read()) as a replacement for Py3. Is this the best practice? Does anyone know a simpler way to do this?

Ryan

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Ryan_Nelson · March 20, 2015, 3:57pm

For me, if I change the script from the PR to what is shown below, everything works fine in both Python 2.7 and 3.4 (Anaconda environments, everything updated):

···

On Fri, Mar 20, 2015 at 11:48 AM, Ryan Nelson <rnelsonchem@…287…> wrote:

Thanks, Ben. I should have made that more clear. If I run the code from the PR, I get the following error:

Traceback (most recent call last):

File “junk.py”, line 11, in

image = pyplot.imread(data) # crash on py3.x

File “/home/nelson/apps/miniconda/lib/python3.4/site-packages/matplotlib/pyplot.py”, line 2215, in imread

return _imread(*args, **kwargs)

File “/home/nelson/apps/miniconda/lib/python3.4/site-packages/matplotlib/image.py”, line 1270, in imread

return handler(fname)

RuntimeError: _image_module::readpng: file not recognized as a PNG file

My code that I’m trying to port essentially does the same thing, and I get the same error. I ran this example just now from Anaconda Python 3.4 install with MPL 1.4.3.

My impression from the PR was that this should work out of the box now. I figured that maybe that was not quite the case. The implementations between Py2 and 3 are quite different. Figured there must be a different way that I wasn’t aware of.

Ryan

On Fri, Mar 20, 2015 at 9:51 AM, Benjamin Root <ben.root@…1304…> wrote:

According to the PR you reference, the fix for this was merged back in Jan 2013, so that means that this fix is in version 1.2.x and up. Are you saying that you still can’t do imread(urllib.request.urlopen(url))?

On Thu, Mar 19, 2015 at 8:54 PM, Ryan Nelson <rnelsonchem@…287…> wrote:

Hello all,

I’m porting over some code that used Py2.7 urllib2.urlopen(url) to grab some image data from the net and load with pyplot.imread. It doesn’t work quite right in Py3.4. I found a couple of refs:

https://github.com/matplotlib/matplotlib/pull/1650

http://stackoverflow.com/questions/15183170/python-crash-when-downloading-image-as-numpy-array

They suggest io.BytesIO(urllib.request.urlopen(url).read()) as a replacement for Py3. Is this the best practice? Does anyone know a simpler way to do this?

Ryan

Dive into the World of Parallel Programming The Go Parallel Website, sponsored

by Intel and developed in partnership with Slashdot Media, is your hub for all

things parallel software development, from weekly thought leadership blogs to

news, videos, case studies, tutorials and more. Take a look and join the

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tacaswell · March 20, 2015, 4:24pm

I think six (which we use to smooth over the 2/3 changes) has a way of dealing with atleast the urllib renaming .

···

On Fri, Mar 20, 2015 at 11:48 AM, Ryan Nelson <rnelsonchem@…287…> wrote:

Thanks, Ben. I should have made that more clear. If I run the code from the PR, I get the following error:

Traceback (most recent call last):

File “junk.py”, line 11, in

image = pyplot.imread(data) # crash on py3.x

File “/home/nelson/apps/miniconda/lib/python3.4/site-packages/matplotlib/pyplot.py”, line 2215, in imread

return _imread(*args, **kwargs)

File “/home/nelson/apps/miniconda/lib/python3.4/site-packages/matplotlib/image.py”, line 1270, in imread

return handler(fname)

RuntimeError: _image_module::readpng: file not recognized as a PNG file

My code that I’m trying to port essentially does the same thing, and I get the same error. I ran this example just now from Anaconda Python 3.4 install with MPL 1.4.3.

My impression from the PR was that this should work out of the box now. I figured that maybe that was not quite the case. The implementations between Py2 and 3 are quite different. Figured there must be a different way that I wasn’t aware of.

Ryan

On Fri, Mar 20, 2015 at 9:51 AM, Benjamin Root <ben.root@…1304…> wrote:

According to the PR you reference, the fix for this was merged back in Jan 2013, so that means that this fix is in version 1.2.x and up. Are you saying that you still can’t do imread(urllib.request.urlopen(url))?

On Thu, Mar 19, 2015 at 8:54 PM, Ryan Nelson <rnelsonchem@…287…> wrote:

Hello all,

I’m porting over some code that used Py2.7 urllib2.urlopen(url) to grab some image data from the net and load with pyplot.imread. It doesn’t work quite right in Py3.4. I found a couple of refs:

https://github.com/matplotlib/matplotlib/pull/1650

http://stackoverflow.com/questions/15183170/python-crash-when-downloading-image-as-numpy-array

They suggest io.BytesIO(urllib.request.urlopen(url).read()) as a replacement for Py3. Is this the best practice? Does anyone know a simpler way to do this?

Ryan

Dive into the World of Parallel Programming The Go Parallel Website, sponsored

by Intel and developed in partnership with Slashdot Media, is your hub for all

things parallel software development, from weekly thought leadership blogs to

news, videos, case studies, tutorials and more. Take a look and join the

conversation now. http://goparallel.sourceforge.net/

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Ryan_Nelson · March 20, 2015, 4:52pm

I can understand that switching from Py 2 to 3 is going to require a change from urllib2.urlopen to urllib.requests.urlopen, but the addition of BytesIO and read() makes the transition tricky. It was not obvious to me why that wouldn’t work right off the bat, which is why I had to dig up that PR and SO post.

As an alternate question, then: would a PR be welcome that makes it so that URL info can be passed directly to the imread function? There’s already a test to see if fname is a string. Maybe a quick check to see if it starts with “http”. Then imread could handle all of this business internally.

Thanks

Ryan

···

On Fri, Mar 20, 2015 at 12:24 PM, Thomas Caswell <tcaswell@…287…> wrote:

I think six (which we use to smooth over the 2/3 changes) has a way of dealing with atleast the urllib renaming .

On Fri, Mar 20, 2015 at 11:58 AM Ryan Nelson <rnelsonchem@…287…> wrote:

For me, if I change the script from the PR to what is shown below, everything works fine in both Python 2.7 and 3.4 (Anaconda environments, everything updated):
##################

url = ‘http://www.libpng.org/pub/png/img_png/pngnow.png’

try:

import urllib2

data = urllib2.urlopen(url)

except Exception:

import urllib.request

from io import BytesIO

data = BytesIO(urllib.request.urlopen(url).read())

from matplotlib import pyplot

image = pyplot.imread(data) # crash on py3.x

pyplot.imshow(image)

pyplot.show()

#################

But as you can see, the Python 3 version requires the addition of BytesIO and read(). I take it that this is not supposed to be the case.

Ryan

Dive into the World of Parallel Programming The Go Parallel Website, sponsored

by Intel and developed in partnership with Slashdot Media, is your hub for all

things parallel software development, from weekly thought leadership blogs to

news, videos, case studies, tutorials and more. Take a look and join the

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On Fri, Mar 20, 2015 at 11:48 AM, Ryan Nelson <rnelsonchem@…287…> wrote:

Thanks, Ben. I should have made that more clear. If I run the code from the PR, I get the following error:

Traceback (most recent call last):

File “junk.py”, line 11, in

image = pyplot.imread(data) # crash on py3.x

File “/home/nelson/apps/miniconda/lib/python3.4/site-packages/matplotlib/pyplot.py”, line 2215, in imread

return _imread(*args, **kwargs)

File “/home/nelson/apps/miniconda/lib/python3.4/site-packages/matplotlib/image.py”, line 1270, in imread

return handler(fname)

RuntimeError: _image_module::readpng: file not recognized as a PNG file

My code that I’m trying to port essentially does the same thing, and I get the same error. I ran this example just now from Anaconda Python 3.4 install with MPL 1.4.3.

My impression from the PR was that this should work out of the box now. I figured that maybe that was not quite the case. The implementations between Py2 and 3 are quite different. Figured there must be a different way that I wasn’t aware of.

Ryan

On Fri, Mar 20, 2015 at 9:51 AM, Benjamin Root <ben.root@…1304…> wrote:

According to the PR you reference, the fix for this was merged back in Jan 2013, so that means that this fix is in version 1.2.x and up. Are you saying that you still can’t do imread(urllib.request.urlopen(url))?

On Thu, Mar 19, 2015 at 8:54 PM, Ryan Nelson <rnelsonchem@…1003…7…> wrote:

Hello all,

I’m porting over some code that used Py2.7 urllib2.urlopen(url) to grab some image data from the net and load with pyplot.imread. It doesn’t work quite right in Py3.4. I found a couple of refs:

https://github.com/matplotlib/matplotlib/pull/1650

http://stackoverflow.com/questions/15183170/python-crash-when-downloading-image-as-numpy-array

They suggest io.BytesIO(urllib.request.urlopen(url).read()) as a replacement for Py3. Is this the best practice? Does anyone know a simpler way to do this?

Ryan

Dive into the World of Parallel Programming The Go Parallel Website, sponsored

by Intel and developed in partnership with Slashdot Media, is your hub for all

things parallel software development, from weekly thought leadership blogs to

news, videos, case studies, tutorials and more. Take a look and join the

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Jerzy_Karczmarczuk · March 20, 2015, 7:41pm

It works for X.png, not for X.jpg. The call of imread() fails then. Tested also under 3.4/Anaconda.

Jerzy Karczmarczuk

···

Le 20/03/2015 16:57, Ryan Nelson a écrit :

For me, if I change the script from the PR to what is shown below, everything works fine in both Python 2.7 and 3.4 (Anaconda environments, everything updated):
##################
url = 'http://www.libpng.org/pub/png/img_png/pngnow.png’
try:
    import urllib2
    data = urllib2.urlopen(url)
except Exception:
    import urllib.request
    from io import BytesIO
    data = BytesIO(urllib.request.urlopen(url).read())

from matplotlib import pyplot

image = pyplot.imread(data) # crash on py3.x
pyplot.imshow(image)
pyplot.show()
#################
But as you can see, the Python 3 version requires the addition of BytesIO and read(). I take it that this is not supposed to be the case.

tacaswell · March 20, 2015, 8:17pm

Despite my grumping earlier, a PR that makes URLs just work is probably a good idea and would be merged.

Tom

···

On Fri, Mar 20, 2015 at 3:59 PM Jerzy Karczmarczuk <jerzy.karczmarczuk@…3937…> wrote:

Le 20/03/2015 16:57, Ryan Nelson a écrit :

For me, if I change the script from the PR to what is shown below,

everything works fine in both Python 2.7 and 3.4 (Anaconda

environments, everything updated):

##################

url = ‘http://www.libpng.org/pub/png/img_png/pngnow.png’

try:
import urllib2
data = urllib2.urlopen(url)
except Exception:
import urllib.request
from io import BytesIO
data = BytesIO(urllib.request.urlopen(url).read())
from matplotlib import pyplot

image = pyplot.imread(data) # crash on py3.x

pyplot.imshow(image)

pyplot.show()

#################

But as you can see, the Python 3 version requires the addition of

BytesIO and read(). I take it that this is not supposed to be the case.

It works for X.png, not for X.jpg. The call of imread() fails then.

Tested also under 3.4/Anaconda.

Jerzy Karczmarczuk

Dive into the World of Parallel Programming The Go Parallel Website, sponsored

by Intel and developed in partnership with Slashdot Media, is your hub for all

things parallel software development, from weekly thought leadership blogs to

news, videos, case studies, tutorials and more. Take a look and join the

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Ryan_Nelson · March 20, 2015, 8:32pm

A little update. It seems that this seems to be specific to Linux in some way. I tried the original script from the PR under a couple of conditions:

on Windows 7 Anaconda Python 2.7 and 3.4 – everything works both versions
on Anaconda Python 2.7 and 3.4 Linux version – only the 2.7 version works
on Gentoo Linux Python 2.7 and 3.4, MPL 1.4.3 – only the 2.7 version works

Hope that helps.

Ryan

···

On Fri, Mar 20, 2015 at 3:41 PM, Jerzy Karczmarczuk <jerzy.karczmarczuk@…3937…> wrote:

Le 20/03/2015 16:57, Ryan Nelson a écrit :

For me, if I change the script from the PR to what is shown below,

everything works fine in both Python 2.7 and 3.4 (Anaconda

environments, everything updated):

##################

url = ‘http://www.libpng.org/pub/png/img_png/pngnow.png’

try:
import urllib2
data = urllib2.urlopen(url)
except Exception:
import urllib.request
from io import BytesIO
data = BytesIO(urllib.request.urlopen(url).read())
from matplotlib import pyplot

image = pyplot.imread(data) # crash on py3.x

pyplot.imshow(image)

pyplot.show()

#################

But as you can see, the Python 3 version requires the addition of

BytesIO and read(). I take it that this is not supposed to be the case.

It works for X.png, not for X.jpg. The call of imread() fails then.

Tested also under 3.4/Anaconda.

Jerzy Karczmarczuk

Dive into the World of Parallel Programming The Go Parallel Website, sponsored

by Intel and developed in partnership with Slashdot Media, is your hub for all

things parallel software development, from weekly thought leadership blogs to

news, videos, case studies, tutorials and more. Take a look and join the

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Ryan_Nelson · March 20, 2015, 8:36pm

Thomas, sorry I missed your email.

I’ll see if I can get a PR pulled together soon-ish.

Ryan

···

On Fri, Mar 20, 2015 at 4:32 PM, Ryan Nelson <rnelsonchem@…287…> wrote:

A little update. It seems that this seems to be specific to Linux in some way. I tried the original script from the PR under a couple of conditions:

on Windows 7 Anaconda Python 2.7 and 3.4 – everything works both versions

on Anaconda Python 2.7 and 3.4 Linux version – only the 2.7 version works

on Gentoo Linux Python 2.7 and 3.4, MPL 1.4.3 – only the 2.7 version works

Hope that helps.

Ryan

On Fri, Mar 20, 2015 at 3:41 PM, Jerzy Karczmarczuk <jerzy.karczmarczuk@…3937…> wrote:

Le 20/03/2015 16:57, Ryan Nelson a écrit :

For me, if I change the script from the PR to what is shown below,

everything works fine in both Python 2.7 and 3.4 (Anaconda

environments, everything updated):

##################

url = ‘http://www.libpng.org/pub/png/img_png/pngnow.png’

try:
import urllib2
data = urllib2.urlopen(url)
except Exception:
import urllib.request
from io import BytesIO
data = BytesIO(urllib.request.urlopen(url).read())
from matplotlib import pyplot

image = pyplot.imread(data) # crash on py3.x

pyplot.imshow(image)

pyplot.show()

#################

But as you can see, the Python 3 version requires the addition of

BytesIO and read(). I take it that this is not supposed to be the case.

It works for X.png, not for X.jpg. The call of imread() fails then.

Tested also under 3.4/Anaconda.

Jerzy Karczmarczuk

Dive into the World of Parallel Programming The Go Parallel Website, sponsored

by Intel and developed in partnership with Slashdot Media, is your hub for all

things parallel software development, from weekly thought leadership blogs to

news, videos, case studies, tutorials and more. Take a look and join the

conversation now. http://goparallel.sourceforge.net/

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