RMagick write fails / to_blob works

ruby-talk
1

I am trying to use @img.write(path) but it's not working (zero bytes written). Using "to_blob" works.

     f = Tempfile.new('tmp_img')
FAILING CODE:
     @img.write(f.path)

WORKING CODE:
     File.open(f.path, 'wb') do |f|
       f.syswrite(@img.to_blob)
     end

Any idea ?

(RMagick 2.5.2)

Thanks for any reply.

Gaspard

2

Gaspard Bucher wrote:

I am trying to use @img.write(path) but it's not working (zero bytes
written). Using "to_blob" works.

     f = Tempfile.new('tmp_img')
FAILING CODE:
     @img.write(f.path)

WORKING CODE:
     File.open(f.path, 'wb') do |f|
       f.syswrite(@img.to_blob)
     end

Image#write doesn't know what to do with a Tempfile object. It can only
accept a string or a File object that's been opened for output.

Image#write calls directly into ImageMagick, and ImageMagick doesn't
know anything about Ruby objects like Tempfiles.

···

--
Posted via http://www.ruby-forum.com/\.

3

Image#write's argument is in fact a String (f.path), not the Tempfile object itself...

···

Gaspard Bucher wrote:

I am trying to use @img.write(path) but it's not working (zero bytes
written). Using "to_blob" works.

    f = Tempfile.new('tmp_img')
FAILING CODE:
    @img.write(f.path)

WORKING CODE:
    File.open(f.path, 'wb') do |f|
      f.syswrite(@img.to_blob)
    end

Image#write doesn't know what to do with a Tempfile object. It can only
accept a string or a File object that's been opened for output.

Image#write calls directly into ImageMagick, and ImageMagick doesn't
know anything about Ruby objects like Tempfiles.
--
Posted via http://www.ruby-forum.com/\.

4

Gaspard Bucher wrote:

Image#write's argument is in fact a String (f.path), not the Tempfile object itself...

Gaspard Bucher wrote:

I am trying to use @img.write(path) but it's not working (zero bytes
written). Using "to_blob" works.

    f = Tempfile.new('tmp_img')
FAILING CODE:
    @img.write(f.path)

WORKING CODE:
    File.open(f.path, 'wb') do |f|
      f.syswrite(@img.to_blob)
    end

Image#write doesn't know what to do with a Tempfile object. It can only
accept a string or a File object that's been opened for output.

Image#write calls directly into ImageMagick, and ImageMagick doesn't
know anything about Ruby objects like Tempfiles.
--
Posted via http://www.ruby-forum.com/\.

It's possibly due to the file already being opened for writing. Try f.close first, then @img.write(f.path).

···

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5

Gaspard Bucher wrote:

Image#write's argument is in fact a String (f.path), not the Tempfile object itself...

I see. I overlooked that earlier.

Normally Image#write either succeeds or raises an exception. I have never seen it silently fail.

If you like, open a support request track on RubyForge with a simple reproduction (just Ruby and RMagick, no Rails, etc.) and let me know what O/S you're on and what version of ImageMagick you have installed. I'll be glad to investigate.

···

--
RMagick: http://rmagick.rubyforge.org/

6

Hi, Gaspard and Tim:

I've tried changing:

@img.write(f.path)

to

@img.write(f.path+'.jpg')

and it works. Maybe RMagick just needs to check if there is an
extension ImageMagick can use.

Cheers,

Serabe

···

--

7

Serabe wrote:

Hi, Gaspard and Tim:

I've tried changing:

@img.write(f.path)

to

@img.write(f.path+'.jpg')

and it works. Maybe RMagick just needs to check if there is an
extension ImageMagick can use.

Cheers,

Serabe

Duh. I had to figure this out just a few weeks ago. I should've remembered. I must be getting old.

The Tempfile path ends in .0, which is not an extension ImageMagick can use. As Serabe so intelligently points out, adding a valid extension works. You can also add a prefix: "jpeg:" + f.path.

Thanks for being smarter than me, Serabe!

···

--
RMagick: http://rmagick.rubyforge.org/

8

You guys rock !

Thanks very much. Adding 'jpeg:' prefix solved the problem. This solution is better because it keeps the temporary filename so the file is still cleaned up.

Solution:

     tmp_path = Tempfile.new('tmp_img').path
     @img.write('jpeg:' + tmp_path) # writes to tmp_path

Thanks !

Gaspard

···

Le 26 août 08 à 00:47, Tim Hunter a écrit :

Serabe wrote:

Hi, Gaspard and Tim:
I've tried changing:
@img.write(f.path)
to
@img.write(f.path+'.jpg')
and it works. Maybe RMagick just needs to check if there is an
extension ImageMagick can use.
Cheers,
Serabe

Duh. I had to figure this out just a few weeks ago. I should've remembered. I must be getting old.

The Tempfile path ends in .0, which is not an extension ImageMagick can use. As Serabe so intelligently points out, adding a valid extension works. You can also add a prefix: "jpeg:" + f.path.

Thanks for being smarter than me, Serabe!

--
RMagick: http://rmagick.rubyforge.org/