image blobs are 1 octet too short? encoding?

[joshco]

I'm trying to use imgkit in a rails controller with send_data and imgkit.to_png
This results in an image sent that is 1 byte too short and a broken image.
However, if I save the data to a file with imgkit.to_file, and then tell rails to send that with send_file it works.
I'm on Windows 10 x64, ruby 2.0, rails 4.2.0, imgkit 1.6.1, wkhtmltoimage 0.12.2.4

I can't figure out what is wrong, but my hunch is that this is an encoding issue. The strings(blobs) show up as ASCII-8BIT

    kit = IMGKit.new(html)
    image_data = kit.to_png
    file = kit.to_file('myfile.png')
    send_file('myfile.png', :type => "image/png", :disposition => 'inline') # THIS WORKS
    send_data image_data, type: 'image/png', :disposition => 'inline' #THIS DOES NOT

[joshco]

More info. I tried re-reading the file that was created with .to_file with IO.binread('myfile.png') into a string variable and then and using that string as a param with send_data and that works.
It looks like the inter-process pipe between imgkit and the wkhtmltoimage executable is where the problem arises.