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Adam Ziemba

2010-Mar-11 23:04 UTC

render a Google Chart to a file

Anyone not familiar with Google Charts, it''s simple, a PNG image is
produced by a configured URL. E.g. follow the link:

http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12

You''ll see a chart that is a PNG image.

Okay so I need to save one of these to a file. I tried using Rails
"render" action, treating the URL as if it were a web page... I might
be
WAY off but I figure what I need is something like this:

  File.open( "chart.png", "w" ) do |the_file|
    the_file.puts render(:url =>
"http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|ELECTRICAL|BUMPER_PINTLEH|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12")
  end

Basically I need to store the contents of what is produced by the image
at that really long Google Charts URL shown above.

I apologize for my newbieness, and thank you for all the help!
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Rob Biedenharn

2010-Mar-12 02:49 UTC

head link

Re: render a Google Chart to a file

On Mar 11, 2010, at 6:04 PM, Adam Ziemba wrote:
> Anyone not familiar with Google Charts, it''s simple, a PNG image
is
> produced by a configured URL. E.g. follow the link:
>
>
http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0
> :|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12
>
> You''ll see a chart that is a PNG image.
>
> Okay so I need to save one of these to a file. I tried using Rails
> "render" action, treating the URL as if it were a web page... I  
> might be
> WAY off but I figure what I need is something like this:
>
>  File.open( "chart.png", "w" ) do |the_file|
>    the_file.puts render(:url =>
>
"http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0
> :|ELECTRICAL|BUMPER_PINTLEH|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12")
>  end
>
> Basically I need to store the contents of what is produced by the  
> image
> at that really long Google Charts URL shown above.
>
> I apologize for my newbieness, and thank you for all the help!
>
Look at open-uri (require ''open-uri'')

open(''http://chart....'') do |chart|
   File.open(''chart.png'', ''w'') {|f| f.write
chart.read }
end

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org



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Adam Ziemba

2010-Mar-18 18:50 UTC

head link

Re: render a Google Chart to a file

> open(''http://chart....'') do |chart|
>    File.open(''chart.png'', ''w'') {|f|
f.write chart.read }
> end
This is wonderful, I knew nothing of open-uri. However, I cannot seem to 
get it pull an image. Using the Google link above, which produces a PNG 
image, I get the error "bad URI(is not URI?)".

Looking at the API for open-uri, I could not find any information about 
images.

I played around with it, I can beautifully retrieve web pages and save 
them to disk, but what about images?

Thanks for the help!
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Adam Ziemba

2010-Mar-18 19:02 UTC

head link

Re: render a Google Chart to a file

I managed to get what seems to be a PNG file saved using an actual URL 
to the image:

  File.open ''image.png'', ''w'' do |file|
    open(''http://link_to_image.png'').path { |chunk| file.write
chunk }
  end

Notice the .png extension which is not present with the Google charts 
URL.

This did save image.png to the file system, however the image is 
invalid. So this did not work even for a straight link to a PNG image.

I''m not going to have to use ImageMagick am I? Please tell me no...
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Colin Law

2010-Mar-18 21:10 UTC

head link

Re: Re: render a Google Chart to a file

On 18 March 2010 18:50, Adam Ziemba
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:>> open(''http://chart....'') do |chart|
>>    File.open(''chart.png'', ''w'') {|f|
f.write chart.read }
>> end
>
> This is wonderful, I knew nothing of open-uri. However, I cannot seem to
> get it pull an image. Using the Google link above, which produces a PNG
> image, I get the error "bad URI(is not URI?)".
I think you have two problems, firstly you need to escape the uri,
this seems to work but there is probably a nicer way of doing it:
   
open("http://chart.apis.google.com/chart#{CGI.escape(''?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12'')}")
do |chart|
      File.open(''chart.png'', ''w'') {|f|
f.write chart.read }
    end

Unfortunately you do not end up with a png file.  If you open the file
with a text editor you will find it is a web page with loads of
javascript.  Presumably the javascript generates the png.  I think you
need an alternative approach.

Colin
>
> Looking at the API for open-uri, I could not find any information about
> images.
>
> I played around with it, I can beautifully retrieve web pages and save
> them to disk, but what about images?
>
> Thanks for the help!
> --
> Posted via http://www.ruby-forum.com/.
>
> --
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>
>
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Adam Ziemba

2010-Mar-19 01:00 UTC

head link

Re: Re: render a Google Chart to a file

Colin Law wrote:
>    
open("http://chart.apis.google.com/chart#{CGI.escape(''?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12'')}")
> do |chart|
>       File.open(''chart.png'', ''w'') {|f|
f.write chart.read }
>     end
I definitely understand the why you would want to escape the URI, but 
I''m not convinced that this approach will never work.

The URL with the escaped characters causes Google to reject it as 
invalid parameters, which is why you got all that HTML and Javascript. 
E.g. if you use your browser to open the result of the above URI with 
escaped characters:

http://chart.apis.google.com/chart%3Fcht%3Dbvg%26chbh%3Da%26chd%3Ds%3Avttusty%26chs%3D500x300%26chxt%3Dx%2Cy%26chxl%3D0%3A%7CSun%7CMon%7CTue%7CWed%7CThu%7CFri%7CSat%7C1%3A%7C0%7C2%7C4%7C6%7C8%7C10%7C12

You are redirected to the Google chart API. Retaining the original 
characters with:

http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12

you''ll get a PNG image and nothing else.

Okay, so Google doesn''t want the escaped characters, and the URI::open 
method doesn''t want the plain characters... or does it? Is there no way
around this? The thing is the characters used in the URL above are 
valid, or so I thought. I pass these kind of characters as parameters 
from controller to view all throughout my application, with full browser 
compatibility.

I tried using backslashes for all the characters, e.g. "\&"
instead of
"&" and the URI open method still rejects it.

I''ve seen some people successfully get images to save to the file
system
using URI, but I''m assuming all their code is outdated as I could not 
get it to work. Also, the image URL they were using actually pointed to 
a PNG image, with a PNG extension, whereas the Google Chart URL will 
return a PNG image.

I appreciate all the help!
-- 
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pharrington

2010-Mar-19 01:23 UTC

head link

Re: render a Google Chart to a file

On Mar 18, 9:00 pm, Adam Ziemba
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:> Colin Law wrote:
> >    
open("http://chart.apis.google.com/chart#{CGI.escape(''?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun
|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12'')}")
> > do |chart|
> >       File.open(''chart.png'', ''w'')
{|f| f.write chart.read }
> >     end
>
> I definitely understand the why you would want to escape the URI, but
> I''m not convinced that this approach will never work.
>
> The URL with the escaped characters causes Google to reject it as
> invalid parameters, which is why you got all that HTML and Javascript.
> E.g. if you use your browser to open the result of the above URI with
> escaped characters:
>
> http://chart.apis.google.com/chart%3Fcht%3Dbvg%26chbh%3Da%26chd%3Ds%3...
>
> You are redirected to the Google chart API. Retaining the original
> characters with:
>
>
http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=5...Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12
>
> you''ll get a PNG image and nothing else.
>
> Okay, so Google doesn''t want the escaped characters, and the
URI::open
> method doesn''t want the plain characters... or does it? Is there
no way
> around this? The thing is the characters used in the URL above are
> valid, or so I thought. I pass these kind of characters as parameters
> from controller to view all throughout my application, with full browser
> compatibility.
>
> I tried using backslashes for all the characters, e.g. "\&"
instead of
> "&" and the URI open method still rejects it.
>
> I''ve seen some people successfully get images to save to the file
system
> using URI, but I''m assuming all their code is outdated as I could
not
> get it to work. Also, the image URL they were using actually pointed to
> a PNG image, with a PNG extension, whereas the Google Chart URL will
> return a PNG image.
>
> I appreciate all the help!
> --
> Posted viahttp://www.ruby-forum.com/.
Seems an inadequacy of Ruby URI library. Curb (Ruby libcurl bindings)
works simply and easily though:

ruby-1.9.1-p376 > require ''open-uri''
 => true
ruby-1.9.1-p376 > png = "http://chart.apis.google.com/chart?
cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|Tue|
Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12"
 => "http://chart.apis.google.com/chart?
cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|Tue|
Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12"
ruby-1.9.1-p376 > open png
URI::InvalidURIError: bad URI(is not URI?):
http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12
        from /home/xeno/.rvm/ruby-1.9.1-p376/lib/ruby/1.9.1/uri/
common.rb:156:in `split''
        from /home/xeno/.rvm/ruby-1.9.1-p376/lib/ruby/1.9.1/uri/
common.rb:174:in `parse''
        from /home/xeno/.rvm/ruby-1.9.1-p376/lib/ruby/1.9.1/uri/
common.rb:626:in `parse''
        from /home/xeno/.rvm/ruby-1.9.1-p376/lib/ruby/1.9.1/open-
uri.rb:32:in `open''
        from (irb):3
        from /home/xeno/.rvm/ruby-1.9.1-p376/bin/irb:15:in
`<main>''
ruby-1.9.1-p376 > require ''curb''
 => true
ruby-1.9.1-p376 > c = Curl::Easy.perform png
 => #<Curl::Easy http://chart.apis.google.com/chart?cht=bvg&chbh=a>
ruby-1.9.1-p376 > File.open("png.png", "w") {|f| f.write
c.body_str}
 => 5445
ruby-1.9.1-p376 >

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Brijesh Shah

2010-Mar-19 05:10 UTC

head link

Re: render a Google Chart to a file

Use following method to get image in file from any url


Net::HTTP.start("#{DOMAIN_URL}") { |http|
        resp = http.get(PARAMS)
        open( "#{OUTPUT_DIR}/#{file_name}.png", ''wb''
) { |file|
          file.write(resp.body)
        }
}

Where DOMAIN_URL: http://chart.apis.google.com
PARAMS: 
/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12


Thanks
Brijesh Shah
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Rob Biedenharn

2010-Mar-19 12:17 UTC

head link

Re: Re: Re: render a Google Chart to a file

On Mar 18, 2010, at 9:00 PM, Adam Ziemba wrote:
> Colin Law wrote:
>
>>   
open("http://chart.apis.google.com/chart#{CGI.escape(''?
>>
cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|
>> Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12'')}")
>> do |chart|
>>      File.open(''chart.png'', ''w'')
{|f| f.write chart.read }
>>    end
>
> I definitely understand the why you would want to escape the URI, but
> I''m not convinced that this approach will never work.
>
> The URL with the escaped characters causes Google to reject it as
> invalid parameters, which is why you got all that HTML and Javascript.
> E.g. if you use your browser to open the result of the above URI with
> escaped characters:
>
>
http://chart.apis.google.com/chart%3Fcht%3Dbvg%26chbh%3Da%26chd%3Ds%3Avttusty%26chs%3D500x300%26chxt%3Dx%2Cy%26chxl%3D0%3A%7CSun%7CMon%7CTue%7CWed%7CThu%7CFri%7CSat%7C1%3A%7C0%7C2%7C4%7C6%7C8%7C10%7C12
>
> You are redirected to the Google chart API. Retaining the original
> characters with:
>
>
http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0
> :|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12
>
> you''ll get a PNG image and nothing else.
>
>
> Okay, so Google doesn''t want the escaped characters, and the
URI::open
> method doesn''t want the plain characters... or does it? Is there
no
> way
> around this? The thing is the characters used in the URL above are
> valid, or so I thought. I pass these kind of characters as parameters
> from controller to view all throughout my application, with full  
> browser
> compatibility.
>
> I tried using backslashes for all the characters, e.g. "\&"
instead of
> "&" and the URI open method still rejects it.
>
> I''ve seen some people successfully get images to save to the file
> system
> using URI, but I''m assuming all their code is outdated as I could
not
> get it to work. Also, the image URL they were using actually pointed  
> to
> a PNG image, with a PNG extension, whereas the Google Chart URL will
> return a PNG image.
>
>
> I appreciate all the help!
You just need a URI that''s technically valid, not just one that  
browsers understand. URI.parse and thus open-uri is rather more strict  
than the other tools suggested.

Here''s an irb session that shows the right way to get a valid URI for  
the chart you want.

$ irb -ruri -ropen-uri -rcgi
irb> orig =
''http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0
:|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12''
=>
"http://chart.apis.google.com/chart?cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0
:|Sun|Mon|Tue|Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12"
irb> md = %r{(https?:)//((?i:[-a-z0-9.]+))(/[^?]+)\??(.*)}.match(orig)
=> #<MatchData:0x391070>
irb> scheme, host, path, query_string = md.captures
=> ["http:", "chart.apis.google.com", "/chart",
"cht=bvg&chbh=a&chd=s:vttusty&chs=500x300&chxt=x,y&chxl=0:|Sun|Mon|Tue|
Wed|Thu|Fri|Sat|1:|0|2|4|6|8|10|12"]
irb> query_string.split(''&'').map{|pair|
pair.split(''='')}
=> [["cht", "bvg"], ["chbh", "a"],
["chd", "s:vttusty"], ["chs",
"500x300"], ["chxt", "x,y"], ["chxl",
"0:|Sun|Mon|Tue|Wed|Thu|Fri|Sat|
1:|0|2|4|6|8|10|12"]]
irb> u = URI.parse "#{scheme}//#{host}"
=> #<URI::HTTP:0x37cf44 URL:http://chart.apis.google.com>
irb> u.path = path
=> "/chart"
irb> u.query = query_string.split(''&'').map{|pair|  
pair.split(''='')}.map{|n,v|
"#{n}=#{CGI.escape(v)}"}.join(''&'')
=>
"cht=bvg&chbh=a&chd=s%3Avttusty&chs=500x300&chxt=x%2Cy&chxl=0%3A
%7CSun%7CMon%7CTue%7CWed%7CThu%7CFri%7CSat%7C1%3A 
%7C0%7C2%7C4%7C6%7C8%7C10%7C12"
irb> open(u.to_s) do |chart|
?>         File.open(''chart.png'', ''w'')
{|f| f.write chart.read }
irb>   end
=> 5445
irb> File.exist?(''chart.png'')
=> true

Note that if you are building up the URI yourself, you could just  
create it with valid escaping on the query string rather than pulling  
it apart and escaping it as you put it back together.

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org

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Rails - Mar 2010 - render a Google Chart to a file

render a Google Chart to a file

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