From: Daniel Nugent <nugend@...>
Date: 2005-06-28T05:24:47+09:00
Subject: Re: What do you want to see in a Sparklines Library?

I'm doing that right now actually, I just want to add the ability to
do data: URIs, which should be pretty easy I think.

It's strange that you can't access my server Adam, is anyone else
having that problem?

On 6/27/05, Carl Youngblood <carl.youngblood@gmail.com> wrote:
> One thing that would make sparklines a lot more universally accessible to
> all browsers would be to get rid of the dependency on data urls. The basic
> idea is to return the proper MIME type to the browser and then just start
> spitting out the raw binary data of the PNG.
> 
> Here is an example:
> 
> #!/usr/bin/ruby
> 
> require 'base64'
> require 'cgi'
> require 'zlib'
> 
> def build_png_chunk(type,data)
> to_check = type + data
> return [data.length].pack("N") + to_check +
> [Zlib.crc32(to_check)].pack("N")
> end
> 
> def build_png(image_rows)
> header = [137, 80, 78, 71, 13, 10, 26, 10].pack("C*")
> raw_data = image_rows.map { |row| [0] + row }.flatten.pack("C*")
> ihdr_data = [image_rows.first.length,
> image_rows.length,
> 8,2,0,0,0].pack("NNCCCCC")
> ihdr = build_png_chunk("IHDR", ihdr_data)
> idat = build_png_chunk("IDAT", Zlib::Deflate.deflate(raw_data))
> iend = build_png_chunk("IEND", "")
> 
> return header + ihdr + idat + iend
> end
> 
> def bumpspark(results)
> white, red, grey = [0xFF,0xFF,0xFF], [0,0,0xFF], [0x99,0x99,0x99]
> rows = results.inject([]) do |ary, r|
> ary << [white]*15 << [white]*15
> ary.last[r/9,4] = [(r > 50 and red or grey)]*4
> ary
> end.transpose
> return build_png(rows)
> end
> 
> 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
> 
> send_to_browser (0..22).map { rand 100 }
> 
> 
> See this in action at the following URL:
> 
> http://youngbloods.org/sparkline.cgi
> 
> Carl
> 
> 


-- 
-Dan Nugent