Trouble streaming images with send_data

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

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

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

JB

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

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

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