Re: Learning Guile web. Stuck on returning an image. (Martyn Smith)

Hi all,

Whilst looking around the guile-user area, I noticed an old question I posted with regards to returning an image in GNU Guile Web. Sadly, I did not add closure to this query. As this question comes up on google search I felt I should respond with a solution. I honestly thought I responded to this. I can only apologies regarding this -- it is unprofessional. Regardless, a late reply is better than no reply at all.

I ended up moving to GNU Artanis in the end. At the time, I was just happy playing around with the Web Example section as presented in the Guile Reference Manual. My code was becoming similar to Artanis in a number of ways (atleast the get, post, etc, functions). Obviously, with GNU Artanis being a much more thought-out framework, it made sense to move over. The great news is that is was very easy to move my code over.

Below is an example code I use to return an image. You should just be able to copy-paste the below code - as long as you have artanis installed and ensured it is pointing to a jpg that exists, just open a browser and type - localhost:1234/image

(use-modules (artanis artanis)
                     (rnrs io ports))

(init-server)

(get "/image"
     (lambda (rc)
       (let* ((port (open-file "s.jpg" "r"))
               (bytes (get-bytevector-all port)))
     (close-port port)
     (response-emit bytes #:headers '((content-type image/jpg))))))

(run #:port 1234)

For my personal website, I pass in an id (ie "/image/{id}") which returns a record from the database, containing the location of the file in question... plus other things (tags, uploader, etc) -- once working I stick it inside an image tag - job done!

Obviously my example does not cover error handling but you get the idea. :-)

I hope this helps

On Mon, May 26, 2014 at 5:00 PM, <address@hidden> wrote:

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Today's Topics:

1. Learning Guile web. Stuck on returning an image. (Martyn Smith)
2. Re: Install Guile 2.0.11 failed on L-Ubuntu 12.04 (Germ?n Arias)
3. Re: Learning Guile web. Stuck on returning an image. (Nala Ginrut)
4. Re: Learning Guile web. Stuck on returning an image. (Neil Jerram)

----------------------------------------------------------------------

Message: 1
Date: Sun, 25 May 2014 23:30:33 +0100
From: Martyn Smith <address@hidden>
To: address@hidden
Subject: Learning Guile web. Stuck on returning an image.
Message-ID:
<address@hidden>
Content-Type: text/plain; charset="utf-8"

Hi guys,

I am attempting to create a website as part of a learning experience with
guile. The code is originally based from ideas in
https://www.gnu.org/software/guile/manual/html_node/Web-Examples.html. My
code has progressed since the "Web Examples" page to support a more MVC
style. So far, so good-ish. :-)

Getting to the point of the email -- I am a bit confused how I would return
a jpg image. For example: -
<img src="" />

The "1234" tells me which file to load and return.

Being primarily a .NET developer, I am struggling to understand how to
achieve such goal in guile. I have tried things like (read-file
"/location/to/image.jpg" "r") but no luck. Also tried to understand
converting to bytes in the documentation but again... no luck. Always
getting a 500 error. Yes, I have included (content-type . (image/jpg)) etc.

Can anyone give me a heads up on how to do such thing? How would I open the
jpg file? How would it be returned?

I don't think its worth providing any code here. I think the Web-Examples
page is the best place to review code, and how I would return an image from
that current codebase, etc.

Thanks for any suggestions.

mart
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Message: 2
Date: Sun, 25 May 2014 17:59:08 -0600
From: Germ?n Arias <address@hidden>
To: Chris Vine <address@hidden>
Cc: address@hidden
Subject: Re: Install Guile 2.0.11 failed on L-Ubuntu 12.04
Message-ID: <address@hidden>
Content-Type: text/plain; charset="iso-8859-1"

On 2014-05-25 03:10:55 -0600 Chris Vine <address@hidden> wrote:

[...]
>
> Yuck.

This is exactly what one does not expect in a free software list, where is supposed the users can share and learn together without being offended.

Germ?n.

------------------------------

Message: 3
Date: Mon, 26 May 2014 08:22:58 +0800
From: Nala Ginrut <address@hidden>
To: Martyn Smith <address@hidden>
Cc: Guile User <address@hidden>
Subject: Re: Learning Guile web. Stuck on returning an image.
Message-ID:
<address@hidden>
Content-Type: text/plain; charset="utf-8"

Hi Martyn!

2014?5?26? ??6:30? "Martyn Smith" <address@hidden>???
>
> Hi guys,
>
> I am attempting to create a website as part of a learning experience with
guile. The code is originally based from ideas in
https://www.gnu.org/software/guile/manual/html_node/Web-Examples.html. My
code has progressed since the "Web Examples" page to support a more MVC
style. So far, so good-ish. :-)
>

If you want to play web with Guile, I suggest Artanis, which is a web
framework for it. It's easier than using the lower web api.

www.web-artanis.com

> Getting to the point of the email -- I am a bit confused how I would
return a jpg image. For example: -
> <img src="" />
>
> The "1234" tells me which file to load and return.
>
> Being primarily a .NET developer, I am struggling to understand how to
achieve such goal in guile. I have tried things like (read-file
"/location/to/image.jpg" "r") but no luck. Also tried to understand
converting to bytes in the documentation but again... no luck. Always
getting a 500 error. Yes, I have included (content-type . (image/jpg)) etc.
>

Please attache you complete code. But I guess what you need is
get-bytevector-all which dwells on (rnrs).
Usually, open file only return a file port, you have to read the content
then.

> Can anyone give me a heads up on how to do such thing? How would I open
the jpg file? How would it be returned?
>
> I don't think its worth providing any code here. I think the Web-Examples
page is the best place to review code, and how I would return an image from
that current codebase, etc.
>
> Thanks for any suggestions.
>
> mart
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Message: 4
Date: Mon, 26 May 2014 10:05:17 +0100
From: Neil Jerram <address@hidden>
To: Martyn Smith <address@hidden>
Cc: address@hidden
Subject: Re: Learning Guile web. Stuck on returning an image.
Message-ID: <address@hidden>
Content-Type: text/plain; charset=us-ascii

Martyn Smith <address@hidden> writes:

> Getting to the point of the email -- I am a bit confused how I would return a
> jpg image. For example: -
> <img src="" />
>
> The "1234" tells me which file to load and return.
>
> Being primarily a .NET developer, I am struggling to understand how to achieve
> such goal in guile. I have tried things like (read-file "/location/to/
> image.jpg" "r") but no luck. Also tried to understand converting to bytes in
> the documentation but again... no luck. Always getting a 500 error. Yes, I have
> included (content-type . (image/jpg)) etc.
>
> Can anyone give me a heads up on how to do such thing? How would I open the jpg
> file? How would it be returned?

I recently had the same problem, and eventually decided that it would be
better to use Guile only for my dynamic content, with a standard web
server for the static content. For the latter I chose lighttpd, and I
can provide more details of my setup if that would be helpful.

But what specifically was the problem? My handler for an image file
(and other static content) looked like this:

(lambda (request request-body uri)
(let* ((fn (apply string-append
static-root
(map (lambda (name)
(string-append "/" name))
uri)))
(content (with-input-from-file fn read-string))
(content-type (cond ((string-match "\\.svg" fn)
'(image/svg+xml))
((string-match "\\.html?" fn)
'(text/html))
((string-match "\\.jpe?g" fn)
'(image/jpeg))
((string-match "\\.png" fn)
'(image/png))
((string-match "\\.css" fn)
'(text/css))
((string-match "\\.js" fn)
'(application/_javascript_))
(else
'(text/plain)))))
(trc 'content-type content-type 'length (string-length content))
(values `((content-type . ,content-type))
content)))

The problem here that 'content' contains binary data that can't be
returned as is in an HTTP response. It needs to be encoded in one of
the HTTP-supported encodings, and a corresponding Content-Encoding
header added to the response.

I think I investigated a little whether Guile's (web ...) modules could
do this, or could easily be enhanced, but decided instead on the
solution described above.

Regards,
Neil

------------------------------

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End of guile-user Digest, Vol 138, Issue 9
******************************************

From:	Martyn Smith
Subject:	Re: Learning Guile web. Stuck on returning an image. (Martyn Smith)
Date:	Thu, 10 Dec 2015 19:44:17 +0000