Rails - Apr 2005 - noob question: how do you display blob image data?

Hi,
I have a photo item described below:

CREATE TABLE photos (
	id                    int unsigned NOT NULL AUTO_INCREMENT default
''0'',
	user_id               int unsigned NOT NULL default ''0'',
        photo                 mediumblob NOT NULL default '''',
        photo_width           int unsigned NOT NULL default
''0'',
        photo_height          int unsigned NOT NULL default
''0'',
        thumbnail             mediumblob NOT NULL default '''',
        thumb_width           int unsigned NOT NULL default
''0'',
        thumb_height          int unsigned NOT NULL default
''0'',
        original              mediumblob NOT NULL default '''',
        original_width        int unsigned NOT NULL default
''0'',
        original_height       int unsigned NOT NULL default
''0'',
        status                tinyint unsigned NOT NULL default
''0'',
	created_on            timestamp(14) NOT NULL,
	updated_on            timestamp(14) NOT NULL,
	PRIMARY KEY (id)
) TYPE=MyISAM;

I want to display the photo, the thumbnail, and the original photo as
images in the list page but I don''t know how to do this.  I know how
to display just one of the images using the send_data like below:

  def show
    @photo = Photo.find(@params[:id])

    send_data @photo.original, :filename => ''photo.jpg'',
:type =>
''image/jpeg'', :disposition => ''inline''
  end

Any help would be appreciated.

Thanks,
Frank

On Wed, Apr 27, 2005, Frank Kim wrote:
> Hi,
> I have a photo item described below:
> 
> CREATE TABLE photos (
> 	id                    int unsigned NOT NULL AUTO_INCREMENT default
''0'',
> 	user_id               int unsigned NOT NULL default ''0'',
>         photo                 mediumblob NOT NULL default
'''',
>         photo_width           int unsigned NOT NULL default
''0'',
>         photo_height          int unsigned NOT NULL default
''0'',
>         thumbnail             mediumblob NOT NULL default
'''',
>         thumb_width           int unsigned NOT NULL default
''0'',
>         thumb_height          int unsigned NOT NULL default
''0'',
>         original              mediumblob NOT NULL default
'''',
>         original_width        int unsigned NOT NULL default
''0'',
>         original_height       int unsigned NOT NULL default
''0'',
>         status                tinyint unsigned NOT NULL default
''0'',
> 	created_on            timestamp(14) NOT NULL,
> 	updated_on            timestamp(14) NOT NULL,
> 	PRIMARY KEY (id)
> ) TYPE=MyISAM;
> 
> I want to display the photo, the thumbnail, and the original photo as
> images in the list page but I don''t know how to do this.  I know
how
> to display just one of the images using the send_data like below:
> 
>   def show
>     @photo = Photo.find(@params[:id])
> 
>     send_data @photo.original, :filename =>
''photo.jpg'', :type =>
> ''image/jpeg'', :disposition =>
''inline''
>   end
> 
> Any help would be appreciated.
Seems to me you could create specialized actions for each (show, thumb,
info, what-have-you) and then use regular img tags (or the equivalent
Rails method) to embed them in the page.

If your actions are serving up raw image data with a content type,
shouldn''t that work?  I''m a bit of a noob myself, so
it''s just a guess
:)
> Thanks,
> Frank

Forgive the apparently dumb question but why does it seem like there
are three ways to access a field:

@user.send(''username'')
@user.username
@user[''username'']

Are all the three ways the same?  If not, what is the difference?

Thanks,
Frank

Frank Kim wrote:
> Forgive the apparently dumb question but why does it seem like there
> are three ways to access a field:
> 
> @user.send(''username'')
> @user.username
> @user[''username'']
and @user.send(:read_attribute, ''username'')
> Are all the three ways the same?  If not, what is the difference?
@user.send(''username'') is identical to @user.username.  With
send you
can do convenient things like iterate over a list of method names and
send each one to the object:
  [:bark, :woof, :beg].each { |method| @dog.send method }
is equivalent to
  @dog.bark; @dog.woof, @dog.beg

@user.username calls the username method if you''ve defined it and falls
back to @user[''username''] otherwise.  The fallback is
implemented using
another sweet Ruby gem, method_missing.  If you define method_missing on
your class you can catch method calls that you haven''t defined!
  class Dog
    def method_missing(method, *arguments)
      puts "#{method}!"
      arguments.each { |arg| puts "  #{arg}" }
    end
  end

  @dog.bark(''arf'', ''aRf'',
''ARF'')

  bark!
    arf
    aRf
    ARF

@user[''username''] calls
@user.read_attribute(''username''), a private
method that does the ''raw'' attribute lookup.  Since
it''s a private
method, you can''t invoke it directly.  But a bit of
@user.send(:read_attribute, ''username'') magic can open any
door.

The short answer is: use @user.username whenever possible.  This way you
don''t have to worry whether it''s a custom method or just
@user[''username''] -- it just works.

Best,
jeremy

http://manuals.rubyonrails.com/read/chapter/56
http://wiki.rubyonrails.com/rails/show/HowtoUploadFiles

HowToUploadFiles used to have the relavant information, but may still
be useful. The first link is "Sending and Receiving Files" and looks
to be what you need.

Essentially You''ll want a controller with something like the following:

def ImagesController < ApplicationController
        caches_page :photo
	def photo
		mod_time = Image.get_mod_time @params[''id'']
		min_time = Time.rfc2822(@request.env["HTTP_IF_MODIFIED_SINCE"])
rescue nil
		if min_time and mod_time > min_time
		  render_text '''', ''304 Not Modified''
		else
			image = Image.find @params[''id'']
			send_data image.photo, :filename => image.filename, :type
=>image.mime, :disposition=>''inline''
		end
	end
end

and then the view would have something like: 
<%=image_tag
url_for(:controller=>''images'',:action=>''photo'',:id=>3),:alt=>whatever%>

Another tip: Use custom sql to avoid loading the blob when you''re just
reading the metadata on the image (i.e. to create the image tag with
alt, title, etc if they''re in the db). I have three thumb sizes, and I
have a custom finder for each one to avoid loading potentially large
db records to just display a thumbnail.

I can distill some more code if you need it, but hopefully this should
give you some direction.

Brian

You have to remember to send correct headers:

Something like this:

	def show
		photo = photo.find(@params[''id''])
		-sVi5de4ipzTkBw0ZPqwsow@public.gmane.org[''Pragma''] =
'' ''
		-sVi5de4ipzTkBw0ZPqwsow@public.gmane.org[''Cache-Control''] =
'' ''
		-sVi5de4ipzTkBw0ZPqwsow@public.gmane.org[''Content-type''] =
''image/jpg''
	
-sVi5de4ipzTkBw0ZPqwsow@public.gmane.org[''Content-Disposition'']
= "attachment;
filename=#{photo.name}"
		-sVi5de4ipzTkBw0ZPqwsow@public.gmane.org[''Accept-Ranges''] =
''bytes''
		-sVi5de4ipzTkBw0ZPqwsow@public.gmane.org[''Content-Length''] =
photo.data.length
	
-sVi5de4ipzTkBw0ZPqwsow@public.gmane.org[''Content-Transfer-Encoding'']
= ''binary''
	
-sVi5de4ipzTkBw0ZPqwsow@public.gmane.org[''Content-Description'']
= ''Image data''
		render_text photo.data
		rescue
			render_text "X"
		
	end


On 4/28/05, Brian L. <zorander-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> http://manuals.rubyonrails.com/read/chapter/56
> http://wiki.rubyonrails.com/rails/show/HowtoUploadFiles
> 
> HowToUploadFiles used to have the relavant information, but may still
> be useful. The first link is "Sending and Receiving Files" and
looks
> to be what you need.
> 
> Essentially You''ll want a controller with something like the
following:
> 
> def ImagesController < ApplicationController
>         caches_page :photo
>         def photo
>                 mod_time = Image.get_mod_time
@params[''id'']
>                 min_time =
Time.rfc2822(@request.env["HTTP_IF_MODIFIED_SINCE"]) rescue nil
>                 if min_time and mod_time > min_time
>                   render_text '''', ''304 Not
Modified''
>                 else
>                         image = Image.find @params[''id'']
>                         send_data image.photo, :filename =>
image.filename, :type
> =>image.mime, :disposition=>''inline''
>                 end
>         end
> end
> 
> and then the view would have something like:
> <%=image_tag
url_for(:controller=>''images'',:action=>''photo'',:id=>3),:alt=>whatever%>
> 
> Another tip: Use custom sql to avoid loading the blob when you''re
just
> reading the metadata on the image (i.e. to create the image tag with
> alt, title, etc if they''re in the db). I have three thumb sizes,
and I
> have a custom finder for each one to avoid loading potentially large
> db records to just display a thumbnail.
> 
> I can distill some more code if you need it, but hopefully this should
> give you some direction.
> 
> Brian
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
> 

-- 
// heikki tunkelo

Frank,

By any chance can you give me an example of how you''re getting the  
image data *to* the database? I''m completely stuck on this and
I''ve
tried every example I could find online.

Would really appreciate seeing some working code.

Kindest regards,
Raymond

On Apr 27, 2005, at 7:02 PM, Frank Kim wrote:
> Hi,
> I have a photo item described below:
>
> CREATE TABLE photos (
>     id                    int unsigned NOT NULL AUTO_INCREMENT  
> default ''0'',
>     user_id               int unsigned NOT NULL default
''0'',
>         photo                 mediumblob NOT NULL default
'''',
>         photo_width           int unsigned NOT NULL default
''0'',
>         photo_height          int unsigned NOT NULL default
''0'',
>         thumbnail             mediumblob NOT NULL default
'''',
>         thumb_width           int unsigned NOT NULL default
''0'',
>         thumb_height          int unsigned NOT NULL default
''0'',
>         original              mediumblob NOT NULL default
'''',
>         original_width        int unsigned NOT NULL default
''0'',
>         original_height       int unsigned NOT NULL default
''0'',
>         status                tinyint unsigned NOT NULL default
''0'',
>     created_on            timestamp(14) NOT NULL,
>     updated_on            timestamp(14) NOT NULL,
>     PRIMARY KEY (id)
> ) TYPE=MyISAM;
>
> I want to display the photo, the thumbnail, and the original photo as
> images in the list page but I don''t know how to do this.  I know
how
> to display just one of the images using the send_data like below:
>
>   def show
>     @photo = Photo.find(@params[:id])
>
>     send_data @photo.original, :filename =>
''photo.jpg'', :type =>
> ''image/jpeg'', :disposition =>
''inline''
>   end
>
> Any help would be appreciated.
>
> Thanks,
> Frank
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>

On 5/2/05, Raymond Brigleb
<ray-THGPwszTed5CpjqP0VxSwUEOCMrvLtNR@public.gmane.org> wrote:
> By any chance can you give me an example of how you''re getting the
> image data *to* the database? I''m completely stuck on this and
I''ve
> tried every example I could find online.
Hi Raymond -

My database schema is a little different, but you should get the idea.
(I''ve snipped out the extraneous stuff in the code below)

Here''s the HTML form used to upload a new image:

<!-- note the enctype attribute must be set as shown -->
<form method="post" action="/fotos/create"
enctype="multipart/form-data">
<!-- File input for the image thumbnail -->
<input type="file" name="foto[thumb]"
id="foto_thumb"/>
<!-- file input for the image itself -->
<input type="file" name="foto[image]"
id="foto_image"/>
</form>

Here''s the action in the controller to which that form submits:

  def create
    # create the foto object with the basic parameters like name,
description, etc.
    @foto = Foto.new(@params[''foto''])

    # read the encoded image data from the form
    @foto.image =
@params[''foto''][''image''].read
    @foto.thumb =
@params[''foto''][''thumb''].read
    
    if @foto.save
      flash[''notice''] = ''Foto was successfully
created.''
      redirect_to :action => ''list''
    else
      render_action ''new''
    end
  end

Here''s the controller''s action for retrieving the image for
display in
a page. You''d use this like <img src="/foto/5/img"
width=...

  def img
  	@foto = Foto.find(@params[''id''])
  	send_data @foto.image, :filename =>
"#{@foto.id}#{@foto.mime_type.extension}",
  		:type => @foto.mime_type.content_type
  end

And here''s an erb snippet for displaying one of these images (assuming
there''s a Foto object in @foto)

<img id="focusImage" src="<%= url_for :controller =>
''fotos'', :action => ''img'',
       :id => @foto.id %>" 
       alt="<%= h(@foto.caption) %>">
 
HTH...

- Sean

On 5/3/05, Sean Santry <santry-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> You''d use this like <img src="/foto/5/img" width=...
Oops. Ignore that bit. That was a typo that I meant to delete.

- Sean