Rails - Feb 2007 - Getting image dimensions with file_column

If I''m using file_column and RMagick to upload images and associate
them
with my database records, what should I do to find out the exact
dimensions of a given image?

I can use the url_for_file_column command to link to them, but I''m not
sure how to find out the image''s height and width in my program.

Thanks!
Jeff

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> If I''m using file_column and RMagick to upload images and
associate them
> with my database records, what should I do to find out the exact
> dimensions of a given image?
>
> I can use the url_for_file_column command to link to them, but I''m
not
> sure how to find out the image''s height and width in my program.
I don''t remember where I got it, but this works for jpegs... used like:

jpeg = JPEG.new("some.jpeg")
puts jpeg.width
puts jpeg.height

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

class JPEG
   attr_reader :width, :height, :bits

   def initialize(file)
     if file.kind_of? IO
       examine(file)
     else
       File.open(file, ''rb'') { |io| examine(io) }
     end
   end

   private
   def examine(io)
     raise ''malformed JPEG'' unless io.getc == 0xFF &&
io.getc == 0xD8 # SOI

     class << io
       def readint; (readchar << 8) + readchar; end
       def readframe; read(readint - 2); end
       def readsof; [readint, readchar, readint, readint, readchar]; end
       def next
         c = readchar while c != 0xFF
         c = readchar while c == 0xFF
         c
       end
     end

     while marker = io.next
       case marker
       when 0xC0..0xC3, 0xC5..0xC7, 0xC9..0xCB, 0xCD..0xCF # SOF markers
         length, @bits, @height, @width, components = io.readsof
         raise ''malformed JPEG'' unless length == 8 +
components * 3
       when 0xD9, 0xDA:  break # EOI, SOS
       when 0xFE:        @comment = io.readframe # COM
       when 0xE1:        io.readframe # APP1, contains EXIF tag
       else              io.readframe # ignore frame
       end
     end
   end
end

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Thanks.  I''m pretty certain RMagick actually has that stuff built into
it, I''m just not sure how to access it from inside my Rails
application.

Jeff

Philip Hallstrom wrote:
> I don''t remember where I got it, but this works for jpegs... used
like:
> 
> jpeg = JPEG.new("some.jpeg")
> puts jpeg.width
> puts jpeg.height

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> Thanks.  I''m pretty certain RMagick actually has that stuff built
into
> it, I''m just not sure how to access it from inside my Rails
application.
Me too, but the less I can use imagemagick the happier I am :)  I was 
really close to copying the source from php''s getimagesize function
which
can do gif, png, and bitmap as well, but found this which was enough for 
me...
>
> Jeff
>
> Philip Hallstrom wrote:
>
>> I don''t remember where I got it, but this works for jpegs...
used like:
>>
>> jpeg = JPEG.new("some.jpeg")
>> puts jpeg.width
>> puts jpeg.height
>
>
> -- 
> Posted via http://www.ruby-forum.com/.
>
> >
>
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Yes, you can get it from RMagick, I believe its the image.cols and
image.rows to obtain the width and height.

If you want to avoid imageMagick, take a look at the commandline tool
jhead, which  will give you that info easily.

http://www.sentex.net/~mwandel/jhead/

John.


Jeff Coleman wrote:
> Thanks.  I''m pretty certain RMagick actually has that stuff built
into
> it, I''m just not sure how to access it from inside my Rails
application.
> 
> Jeff
> 
> Philip Hallstrom wrote:
> 
>> I don''t remember where I got it, but this works for jpegs...
used like:
>> 
>> jpeg = JPEG.new("some.jpeg")
>> puts jpeg.width
>> puts jpeg.height
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What I''m trying to do is get access to this information from within my 
Rails program.

Assuming I have a model such as User, with an "image" field, what
I''m
trying to do is get access to dimensions of the User''s image.

I know how to do url_for_file_column(''user'',
''image''), but how would I
get access to the dimensions, how would I create the RMagick/ImageMagick 
object to call on the "cols" and "rows" methods?

I''m surprised this doesn''t seem to have come up for any
others, or
perhaps I''m just missing something.  I don''t think a
command-line tool
is quite what I''m looking for, because I want my controller and view to
have access to these numbers.

Assuming that I have a User object with an "image" field created by
the
file_column plugin, does anyone know exactly how I could access the 
RMagick object for that image?

Jeff

Guest wrote:
> Yes, you can get it from RMagick, I believe its the image.cols and
> image.rows to obtain the width and height.
> 
> If you want to avoid imageMagick, take a look at the commandline tool
> jhead, which  will give you that info easily.
> 

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This is not a very helpful answer to your problem, but I looked at 
file_column and acts_as_attachment. I found the latter to be nicer for 
working with images. I am able to access image geometry with 
acts_as_attachment.

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Guest wrote:
> Yes, you can get it from RMagick, I believe its the image.cols and
> image.rows to obtain the width and height.
> 
It is actually image.columns and image.rows





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