I need help installing pypng in Python 3.3

[ic...@tagyourself.com]

Hello all,

I am very new to python. I am currently porting a little project of mine from java to python and I need to be able to construct and write png images. I naturally turned myself toward pypng to accomplish this.

I learned from the net that pypng 0.0.13 is supposed to work in Python 3.x when run through '2to3'. However, in my case, it apparently does not.

I ran into various problems when trying to install it, some of them I could fix myself. First I attempted to install pip but I couldn't get Windows to recognize pip as an internal command as the prompt informs me.
Then I tried to directly run "setup.py install" from the pypng folder. It didn't work as I got a syntax error. I noticed that in the beginning of the installation process, the following warning was displayed: "conf[use_2to3 = true] unrecognized configuration option"

At that point I was already pretty pissed but I managed to make the warning disappear by updating (installing?) distribute. After that there are no more errors during the installation process and everything seems to work fine. (This seems still strange to me as 2to3 was present in Tools/Script out of the box)


I use pydev in Eclipse and pydev reports several error in png.py anytime I want to import or use it. When trying to import from IDLE I get:

except ValueError, e:
^
Syntax error, line 1863

that paricular error I was able to fix by changing it to "except ValueError as e:" but I don't understand why 2to3 didn't do it automatically.
There are several more errors reported by pydev, here are a few:

line 1368 : "raise ValueError('Chunk %s too short for checksum.', tag)"
Undefined variable: tag

line 2736 : "rows = [map(numpy.uint16, range(0,0x10000,0x5555))]"
Undefined variable from import: uint16


The second one made me suspect I needed to install numpy too. As there are no installers for numpy aimed toward Python3.3.

I decided to install Python2.7 and retry the whole process. Unfortunately I didn't get much more success. I get the exact same errors in pydev when using the 2.7 version of the interpreter and I cannot install numpy either because when I run the .exe file aimed toward Python 2.7 i get the error message:

"Python version 2.7 required, which was not found in the registry"

I then have the option to manually enter the path to Python 2.7 but the textform is greyed out and I can't type in anything.


At that point I decided to go look for help and Here I am...

I am truly grateful to anyone who takes the time to help me in this matter.
Thank you!

[ic...@tagyourself.com]

I probably should have mentioned that I'm under W7 ultimate x64, I'm using eclipse Juno (latest) and pydev 2.7.1

[Andrew Robinson]

On 10/29/2012 05:23 AM, icgwh wrote:
> Hello all,
>
> I am very new to python. I am currently porting a little project of mine from java to python and I need to be able to construct and write png images. I naturally turned myself toward pypng to accomplish this.

I don't know if this will help, but:

There is a package called image magic; which can convert any image to
any other type of image.
If that would not be a burden to install (most OS's have pre-compiled
working binaries) -- you could easily write a portable bitmap file to
disk using python (even without a library) -- and then convert it to png.

I have a little script I wrote in python to create a canvas, and allow
you to draw on it using very simple line drawing primitives, and then
save it to PBM. It's simple enough (only draws lines with different
pens) that you could examine it and write your own script to do the same
or better.

If this interests you, I will see if I can post the py script; or email
it to you.

--Andrew.

[ic...@tagyourself.com]

That's very kind of you but I don't think it would be particularly fitted to my needs. The program I'm trying to code creates an image as an 2D array of "pixels" which is defined by RGBA value. My program needs to access and modifies every component of every pixels in the image following a set of rules, kind of like the game of life, only more complex.

In fact I only need a library to "push" this array of pixels in a displayable format for the GUI and in PNG format to write the image to disk. I don't need to do any fancy stuff with the image, just being able to display and write it.

[ic...@tagyourself.com]

[David Robinow]

On Mon, Oct 29, 2012 at 8:23 AM, <ic...@tagyourself.com> wrote:
> Hello all,
>
> I am very new to python. I am currently porting a little project of mine from java to python and I need to be able to construct and write png images. I naturally turned myself toward pypng to accomplish this.
>
> I learned from the net that pypng 0.0.13 is supposed to work in Python 3.x when run through '2to3'. However, in my case, it apparently does not.
>

You haven't shown that.

> I ran into various problems when trying to install it, some of them I could fix myself. First I attempted to install pip but I couldn't get Windows to recognize pip as an internal command as the prompt informs me.

No, it's not an internal command, but you don't need that. I'm
assuming your python is installed under C:\Python33. If not, adjust as
needed. Try:
C:\Python33\Scripts\pip install pypng

[You didn't say what you did to install pip so I don't know if pip.exe
actually exists in C:\Python33\Scripts]

> Then I tried to directly run "setup.py install" from the pypng folder. It didn't work as I got a syntax error. I noticed that in the beginning of the installation process, the following warning was displayed: "conf[use_2to3 = true] unrecognized configuration option"

The following works for me:
C:\Python33\python setup.py install

>
> At that point I was already pretty pissed but I managed to make the warning disappear by updating (installing?) distribute. After that there are no more errors during the installation process and everything seems to work fine. (This seems still strange to me as 2to3 was present in Tools/Script out of the box)

It's not clear what you did here. setup.py should run 2to3 for you.
What command did you use to successfully? install it?

> I use pydev in Eclipse and pydev reports several error in png.py anytime I want to import or use it. When trying to import from IDLE I get:
>
> except ValueError, e:
> ^
> Syntax error, line 1863

It's clear that the install process didn't run 2to3.

> that paricular error I was able to fix by changing it to "except ValueError as e:" but I don't understand why 2to3 didn't do it automatically.

2to3 does do it automatically.

> There are several more errors reported by pydev, here are a few:
>
> line 1368 : "raise ValueError('Chunk %s too short for checksum.', tag)"
> Undefined variable: tag

Looking at the code, this appears to be a bug.

>
> line 2736 : "rows = [map(numpy.uint16, range(0,0x10000,0x5555))]"
> Undefined variable from import: uint16
>
> The second one made me suspect I needed to install numpy too. As there are no installers for numpy aimed toward Python3.3.

A few lines above there's a try/except for importing numpy. It should
skip this test if numpy is not available. I'm not sure how you were
able to execute that line [unless you've got a stray numpy.py file
somewhere somewhere]

> I decided to install Python2.7 and retry the whole process. Unfortunately I didn't get much more success. I get the exact same errors in pydev when using the 2.7 version of the interpreter and I cannot install numpy either because when I run the .exe file aimed toward Python 2.7 i get the error message:
>
> "Python version 2.7 required, which was not found in the registry"
>
> I then have the option to manually enter the path to Python 2.7 but the textform is greyed out and I can't type in anything.
>

Do you have the file c:\Python33\Lib\site-packages\pypng-0.0.13-py3.3.egg ?
If not, you have not successfully installed pypng. Please try one of
the methods I gave above.

[ic...@tagyourself.com]

>
> Do you have the file c:\Python33\Lib\site-packages\pypng-0.0.13-py3.3.egg ?
>
> If not, you have not successfully installed pypng. Please try one of
>
> the methods I gave above.

Yes I do have the egg.

I'm gonna try to summarize:

I don't have installations problems anymore but it seems that png.py is not run through 2to3 although it should since the setup.py is properly configured:

if sys.version_info >= (3,):
conf['use_2to3'] = True

I even tried to skip the if to ensure the second line is executed but nothing changed.

I don't know what I'm doing wrong but it seems that png.py is not properly translated to Python 3.

[ic...@tagyourself.com]

>
> Do you have the file c:\Python33\Lib\site-packages\pypng-0.0.13-py3.3.egg ?
>
> If not, you have not successfully installed pypng. Please try one of
>
> the methods I gave above.

[Andrew Robinson]

On 10/29/2012 06:39 AM, ic...@tagyourself.com wrote:
> That's very kind of you but I don't think it would be particularly fitted to my needs. The program I'm trying to code creates an image as an 2D array of "pixels" which is defined by RGBA value. My program needs to access and modifies every component of every pixels in the image following a set of rules, kind of like the game of life, only more complex.
>
> In fact I only need a library to "push" this array of pixels in a displayable format for the GUI and in PNG format to write the image to disk. I don't need to do any fancy stuff with the image, just being able to display and write it.
>
>

Then, actually, what I am suggesting was *almost* perfect.
To do transparency, you need to write the portable any map (PAM) formation.

Simply print a text header to a file which says:

P7
WIDTH 10
HEIGHT 10
DEPTH 4
MAXVAL 255
TUPLTYPE RGB_ALPHA
ENDHDR

And then dump your 2D array to that same file.
A very quick example in 17 lines of code:

io = open( "anyname.pam","w")
x,y = 10,10
gray=(128,128,128,255) # R,G,B,A value
picture = [ [ gray ] * x ] * y # Make a blank gray canvas 2D array

# Do whatever you want to the 2D picture array here!

io.write( "P7\nWIDTH %d\nHEIGHT %d\nDEPTH 4\nMAXVAL 255\nTUPLTYPE
RGB_ALPHA\nENDHDR\n" % (x,y) )

for yi in xrange( y ):
for xi in xrange( x ):
pixel = picture[yi][xi]
io.write( chr(pixel[0]) ) # R value
io.write( chr(pixel[1]) ) # G value
io.write( chr(pixel[2]) ) # B value
io.write( chr(pixel[3]) ) # A value
io.flush()

io.close()

And that's it. You may of course make this more efficient -- I'm just
showing it this way for clarity.
Many programs can read PAM directly; but for those that can't you can
use nettools, or imagemagick, to convert it to PNG.

[ic...@tagyourself.com]

That's really interesting! Thank you so much! Never heard of PAM before... I will try that!

[ic...@tagyourself.com]

On Monday, October 29, 2012 3:48:09 PM UTC+1, Andrew Robinson wrote: