send_data => invalid byte sequence in US-ASCII

I'm trying to display a generated .png plot via send_data(), but it
results in a server error "invalid byte sequence in US-ASCII" error.
I'm pretty sure this means that I need to specify the encoding
somewhere, but I haven't been able to figure out where or how to do so.

Some particulars:

I'm running gnuplot through a pipe to generate a plot in .png format.
(I've tested the code by writing its output to a file and displaying it
-- it works.) My Report model receives the .png image as a string:

  class Report << ActiveRecord::Base
    def imagedata
      image = GnuPlot(@gnuplot_commands)
    end
  end

My Controller uses send_data() to serve up a page:

  class ReportsController < ApplicationController
    def plot
      report = Report.find(params[:id])
      send_data(report.imagedata, :type => 'image/gif')
    end
  end

[FWIW, without really understanding it, I also tried added an :encoding
=> 'utf8' to the send_data call -- no change.] Finally, my View presents
the result:

  <img src="<%= url_for(:controller => 'reports', :action => 'plot')
-%>" />

However, the send_data() call results in a server error:

ArgumentError (invalid byte sequence in US-ASCII):
  <internal:prelude>:8:in `synchronize'
  .../Ruby/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service'

So the question: Where do I specify the encoding? And what encoding is
appropriate for a .png binary?

BTW:
"rails --version" => Rails 2.3.5
"ruby --version" => ruby 1.9.1p376
"mysqul --vesion" => Ver 14.14 Distrib 5.1.36
OS = Mac OS X 10.5.8

I dont know if it's related to the actual error message you are
getting, but I believe your send_data call should look more like this:
send_data(report.imagedata, :disposition => 'inline', :type => 'image/
png', :filename => "graph.png")
You are setting it to a GIF, and not setting the disposition to
inline.

Sharagoz wrote:

I dont know if it's related to the actual error message you are
getting, but I believe your send_data call should look more like this:
send_data(report.imagedata, :disposition => 'inline', :type => 'image/
png', :filename => "graph.png")
You are setting it to a GIF, and not setting the disposition to
inline.

Sharagoz:

Thanks --

* I'd already set the disposition to inline (forgot to mention that,
thanks).

* I tried setting the image type to image/png -- no change. (I'd
thought that png was a subset of gif, but I know now the acronym means
"Png's Not Gif" :slight_smile:

* This *may* be a Ruby 1.9.1 bug -- see
https://rails.lighthouseapp.com/projects/8994/tickets/3941

* I now understand the :filename suggestion - thanks.

Anyway, still broken. For now, I've worked around it using send_file
instead.

- ff