From: Carl Youngblood <carl.youngblood@...>
Date: 2005-06-28T04:02:45+09:00
Subject: Re: What do you want to see in a Sparklines Library?

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Here's an improvement. Make your CGI script accept parameters so that you=
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can make a generic script that will generate sparklines for all types of=20
data:

...

cgi =3D CGI.new
data =3D cgi['data']
if data.empty?
send_to_browser (0..22).map { rand 100 }
else
send_to_browser data.split(',').collect! {|e| e.to_i}
end

Example in action:

http://youngbloods.org/sparkline2.cgi?data=3D23,19,67,20,5

Carl

On 6/27/05, Carl Youngblood <carl.youngblood@gmail.com> wrote:
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> One thing that would make sparklines a lot more universally accessible to=
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> all browsers would be to get rid of the dependency on data urls. The basi=
c=20
> idea is to return the proper MIME type to the browser and then just start=
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> spitting out the raw binary data of the PNG.
>=20
> Here is an example:
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> #!/usr/bin/ruby
>=20
> require 'base64'
> require 'cgi'
> require 'zlib'
>=20
> def build_png_chunk(type,data)
> to_check =3D type + data
> return [data.length].pack("N") + to_check +
> [Zlib.crc32(to_check)].pack("N")
> end
>=20
> def build_png(image_rows)
> header =3D [137, 80, 78, 71, 13, 10, 26, 10].pack("C*")
> raw_data =3D image_rows.map { |row| [0] + row }.flatten.pack("C*")
> ihdr_data =3D [image_rows.first.length,
> image_rows.length,
> 8,2,0,0,0].pack("NNCCCCC")
> ihdr =3D build_png_chunk("IHDR", ihdr_data)
> idat =3D build_png_chunk("IDAT", Zlib::Deflate.deflate(raw_data))
> iend =3D build_png_chunk("IEND", "")
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> return header + ihdr + idat + iend
> end
>=20
> def bumpspark(results)
> white, red, grey =3D [0xFF,0xFF,0xFF], [0,0,0xFF], [0x99,0x99,0x99]
> rows =3D results.inject([]) do |ary, r|
> ary << [white]*15 << [white]*15
> ary.last[r/9,4] =3D [(r > 50 and red or grey)]*4
> ary
> end.transpose
> return build_png(rows)
> end
>=20
> def send_to_browser(results)
> puts "Content-type: image/png"
> puts "Expires: Wed, 11 Nov 1998 11:11:11 GMT"
> puts "Cache-Control: no-cache"
> puts "Cache-Control: must-revalidate"
> puts
> print bumpspark(results)
> end
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> send_to_browser (0..22).map { rand 100 }
>=20
>=20
> See this in action at the following URL:
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> http://youngbloods.org/sparkline.cgi
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> Carl
>

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