Dynamic image creation for the web...

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  • Tompa
    #1

    Dynamic image creation for the web...

    Hi,

    I would like to create images on the fly as a response to an http request.
    I can do this with PIL like this (file create_gif.py):
    from PIL import Image, ImageDraw

    print 'Status: 200 OK'
    print 'Content-type: text/html'
    print
    print '<HTML><HEAD><T ITLE>Python Dynamic Image Creation Test</TITLE></HEAD>'
    print '<BODY>'
    im = Image.new("P", (600, 400))
    draw = ImageDraw.Draw( im)
    draw.rectangle( (0, 0) + im.size, fill="blue")
    im.save("images/tmp.gif");
    print '<img src="/scripts/images/tmp.gif">'
    print '</BODY>'


    However, I would like to 1) avoid saving the image in a file on disk and
    2) separate the HTLM code from the python image creation code.

    Something like this is what I have in mind:
    (file index.html):
    <html>
    <head><meta HTTP-EQUIV="content-type" CONTENT="text/html; charset=UTF-8">
    <title>Python Dynamic Image Creation</title>
    </head>
    <IMG SRC="/scripts/create_image.py " ALT="Image created on the fly...">
    </html>

    and in file create_image.py :
    from PIL import Image, ImageDraw, ImageFont
    im = Image.new("P", (600, 400))
    draw = ImageDraw.Draw( im)
    draw.rectangle( (0, 0) + im.size, fill="blue")


    Unfortunately this does not work :-(
    What is missing?

    Thanks in advance!
    /Tompa


    Tags: None
    • Benjamin Niemann
      #2
      Re: Dynamic image creation for the web...

      Tompa wrote:
      [color=blue]
      > Hi,
      >
      > I would like to create images on the fly as a response to an http request.
      > I can do this with PIL like this (file create_gif.py):
      > from PIL import Image, ImageDraw
      >
      > print 'Status: 200 OK'
      > print 'Content-type: text/html'
      > print
      > print '<HTML><HEAD><T ITLE>Python Dynamic Image Creation
      > Test</TITLE></HEAD>' print '<BODY>'
      > im = Image.new("P", (600, 400))
      > draw = ImageDraw.Draw( im)
      > draw.rectangle( (0, 0) + im.size, fill="blue")
      > im.save("images/tmp.gif");
      > print '<img src="/scripts/images/tmp.gif">'
      > print '</BODY>'
      >
      >
      > However, I would like to 1) avoid saving the image in a file on disk and
      > 2) separate the HTLM code from the python image creation code.
      >
      > Something like this is what I have in mind:
      > (file index.html):
      > <html>
      > <head><meta HTTP-EQUIV="content-type" CONTENT="text/html; charset=UTF-8">
      > <title>Python Dynamic Image Creation</title>
      > </head>
      > <IMG SRC="/scripts/create_image.py " ALT="Image created on the fly...">
      > </html>
      >
      > and in file create_image.py :
      > from PIL import Image, ImageDraw, ImageFont
      > im = Image.new("P", (600, 400))
      > draw = ImageDraw.Draw( im)
      > draw.rectangle( (0, 0) + im.size, fill="blue")
      >
      >
      > Unfortunately this does not work :-(
      > What is missing?[/color]

      You are almost there. Your create_image.py does not return anything to the
      browser yet.

      First return proper HTTP headers, e.g.

      sys.stdout.writ e('Status: 200 OK\r\n')
      sys.stdout.writ e('Content-type: image/gif\r\n')
      sys.stdout.writ e('\r\n')

      (Your prints above are mostly equivalent, but do not output the correct \r\n
      as line terminator - at least on UNIX style systems. Most webservers
      tolarate this, if it's coming from a CGI - but doing it right and not
      relying on a certain server behaviour is not bad anyway ;)

      Then check the PIL docs to find out, how to output the image to sys.stdout
      (instead of writing to a file).

      --
      Benjamin Niemann
      Email: pink at odahoda dot de
      WWW: http://www.odahoda.de/

        Comment

        • Max Erickson
          #3
          Re: Dynamic image creation for the web...

          Tompa <tompa1969@yaho o.com> wrote in
          news:mailman.86 .1125225066.822 9.python-list@python.org :
          [color=blue]
          > Hi,
          >
          > I would like to create images on the fly as a response to an http
          > request. I can do this with PIL like this (file create_gif.py):
          > from PIL import Image, ImageDraw
          >[/color]

          check out sparklines:

          404 Page not found
          http://bitworking.org/projects/sparklines/
          Joe Gregorio - REST, Web, Go, APIs, Dad, Husband, Maker, or any linear combination of such. Googler.


          It is a script very similar to what you want to do.

          The difference between your script and sparklines is mostly that it
          sends:

          print "Content-type: image/png"

          instead of:

          print 'Content-type: text/html'


          max

            Comment

            • Tompa
              #4
              Re: Dynamic image creation for the web...

              Benjamin Niemann <pink <at> odahoda.de> writes:[color=blue]
              > You are almost there.[/color]
              I don't feel so...
              [color=blue]
              > Your create_image.py does not return anything to the
              > browser yet.[/color]
              Yes, I am aware of that but I do not what to return.
              [color=blue]
              > First return proper HTTP headers, e.g.
              >
              > sys.stdout.writ e('Status: 200 OK\r\n')
              > sys.stdout.writ e('Content-type: image/gif\r\n')
              > sys.stdout.writ e('\r\n')[/color]

              Ok, but if possible I'd rather not return anything HTTP/HTML-related from my
              create_image.py file.
              [color=blue]
              > Then check the PIL docs to find out, how to output the image to sys.stdout
              > (instead of writing to a file).
              >[/color]
              Ok, then I get this:

              from PIL import Image, ImageDraw
              import sys

              im = Image.new("P", (600, 400))
              draw = ImageDraw.Draw( im)
              draw.rectangle( (0, 0) + im.size, fill="blue")

              sys.stdout.writ e('Status: 200 OK\r\n')
              sys.stdout.writ e('Content-type: image/gif\r\n')
              sys.stdout.writ e('\r\n')

              im.save(sys.std out, "GIF")

              But this does not work.
              I also tested to skip the HTTP-header stuff and just write the gif to
              sys.stdout, believing that that would work. But not so...

              Hmm, I'm a newbie to Python (as you already probably have noticed ;-) so I
              don't know what else I should try. Any hints are welcome!

              /Tompa


                Comment

                • Tompa
                  #5
                  Re: Dynamic image creation for the web...

                  Max Erickson <maxerickson <at> gmail.com> writes:[color=blue]
                  >
                  > check out sparklines:
                  >
                  > http://bitworking.org/projects/sparklines/
                  >
                  > It is a script very similar to what you want to do.[/color]

                  This sure looks interesting! Strange that I couldn't find this when I googled
                  for this kind of stuff...
                  I will check it out - thanks!

                  Regards,
                  /Tompa


                    Comment

                    • Benjamin Niemann
                      #6
                      Re: Dynamic image creation for the web...

                      Tompa wrote:
                      [color=blue]
                      > Benjamin Niemann <pink <at> odahoda.de> writes:[color=green]
                      >> You are almost there.[/color]
                      > I don't feel so...
                      >[color=green]
                      >> Your create_image.py does not return anything to the
                      >> browser yet.[/color]
                      > Yes, I am aware of that but I do not what to return.
                      >[color=green]
                      >> First return proper HTTP headers, e.g.
                      >>
                      >> sys.stdout.writ e('Status: 200 OK\r\n')
                      >> sys.stdout.writ e('Content-type: image/gif\r\n')
                      >> sys.stdout.writ e('\r\n')[/color]
                      >
                      > Ok, but if possible I'd rather not return anything HTTP/HTML-related from
                      > my create_image.py file.[/color]

                      When the browser fetches the images for displaying, it performs just another
                      HTTP request, and you must reply with a valid HTTP response. The
                      Content-type header is the absolute minimum that must always be returned.
                      (IIRC the 'Status' can be omitted, if it's 200).
                      [color=blue][color=green]
                      >> Then check the PIL docs to find out, how to output the image to
                      >> sys.stdout (instead of writing to a file).
                      >>[/color]
                      > Ok, then I get this:
                      >
                      > from PIL import Image, ImageDraw
                      > import sys
                      >
                      > im = Image.new("P", (600, 400))
                      > draw = ImageDraw.Draw( im)
                      > draw.rectangle( (0, 0) + im.size, fill="blue")
                      >
                      > sys.stdout.writ e('Status: 200 OK\r\n')
                      > sys.stdout.writ e('Content-type: image/gif\r\n')
                      > sys.stdout.writ e('\r\n')
                      >
                      > im.save(sys.std out, "GIF")
                      >
                      > But this does not work.
                      > I also tested to skip the HTTP-header stuff and just write the gif to
                      > sys.stdout, believing that that would work. But not so...[/color]

                      Works perfectly here...
                      What does the error.log of the webserver say?
                      [color=blue]
                      > Hmm, I'm a newbie to Python (as you already probably have noticed ;-) so I
                      > don't know what else I should try. Any hints are welcome!
                      >
                      > /Tompa[/color]

                      --
                      Benjamin Niemann
                      Email: pink at odahoda dot de
                      WWW: http://www.odahoda.de/

                        Comment

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