Trouble streaming images with send_data

Rails
1

Hi

I’m doing some server-side graphics with Java2D and I’m trying to
stream the resulting image to the browser using send_data. When I try
to view the image that I streamed, the browser just shows the URL in
the window as a very small image (about .4 kb) when I am using jpeg
format. For png, it tells me that the image has errors and can’t load
it.

Here’s what I’m doing in the controller:

def sendImage
biFiltered = BI.new(100, 100, BI::TYPE_INT_RGB)
big = biFiltered.createGraphics()
$w = 0
$h = 0
begin
filename = “#{RAILS_ROOT}/public/images/kids.jpg”
imagefile = java.io.File.new(filename)
bi = javax.imageio.ImageIO.read(imagefile)
w = bi.getWidth(nil);
h = bi.getHeight(nil);
if bi.getType != BI.TYPE_INT_RGB
bi2 = BI.new(w, h, BI::TYPE_INT_RGB)
big = bi2.createGraphics()
$stderr.print “after getting graphics”
big.drawImage(biFiltered, 0, 0, nil)
bi = b2
biFiltered = bi
end
rescue
$stderr.print “Couldn’t load file”
end

    big.drawImage(biFiltered,

java.awt.geom.AffineTransform.getScaleInstance(2, 2), nil)
os = java.io.ByteArrayOutputStream.new
begin
isWritten = javax.imageio.ImageIO.write(biFiltered,
“jpeg”, os)
rescue
$stderr.print “Couldn’t write file”
end

    if isWritten
       send_data "os.toByteArray", :type => "image/

jpeg", :disposition => “inline”, :filename => “scaledkids.jpg”
end
end

And then in the HTML file, I just point to the sendImage action from
an img tag.

Does anyone have advice on this? Should I not use the
ByteArrayOutputSteam. It seems that others have used this without
problems.

Thanks.
JB

2

On 15 Apr 2008, at 21:53, jlesleyball wrote:

Hi
if isWritten
send_data “os.toByteArray”, :type => “image/
jpeg”, :disposition => “inline”, :filename => “scaledkids.jpg”

You’re just sending the string “os.toByteArray” rather than the actual
image bytes. I haven’t the faintest clue what a ByteArrayOutputSteam,
but for it to work with send_date you’re going to have to make it look
like a ruby string (which is just a chunk of bytes), i’m sure there’s
some jruby cleverness to assist with that sort of thing.

Fred

3

Thank you, Fred. I will look into the ruby string. And sorry,
everyone, for posting this message twice–accidentally hit send too
soon.

JB

4

According to the following information, I’d have to do some array
allocation/copying or something like that to write Java output streams
directly to the backing byte array of Ruby strings because this
doesn’t seem to have been implemented yet?

http://jira.codehaus.org/browse/JRUBY-929

Could anyone give me a hint on how to perform the workaround?

Thanks

5

This is just a guess based on 5 minutes of looking at the jruby wiki,
but
http://wiki.jruby.org/wiki/Calling_Java_from_JRuby#Ruby_String_to_Java_Bytes_and_back_again
might be interesting.

Fred