Tk supports only GIF?

Ruby
1

I has this snippet to show images:

require ‘tk’

TkLabel.new do
image TkPhotoImage.new(‘file’=> ‘world.gif’)
end.pack

Tk.mainloop

But if I point it to some PNG or JPEG file, I get a “couldn’t recognize
data in image file” exception. If I add an explicit ‘format’ => ‘png’, I
get a “image file format ‘png’ is not supported” exception.

I’m using Ubuntu.

Doesn’t Tk support JPGs and PNGs out of the box?

2

From: Albert S. [email protected]
Subject: Tk supports only GIF?
Date: Thu, 22 Jan 2009 21:58:54 +0900
Message-ID: [email protected]

I’m using Ubuntu.

Doesn’t Tk support JPGs and PNGs out of the box?

If you talk about standard Tcl/Tk only, the answer is “YES”
(see “man n photo”).
To support JPEGs, PNGs, and so on, Tcl/Tk needs “Img” extension.

Possibly, ubuntu package name is “libtk-img”.

When your Tcl/Tk has “Img” extension, Ruby/Tk also supports it.
Please call “require ‘tkextlib/tkimg’”, and you can use JPEGs and
PNGs on your Ruby/Tk.

3

Hidetoshi NAGAI wrote:

Possibly, ubuntu package name is “libtk-img”.
[…]
Please call “require ‘tkextlib/tkimg’”

Thanks! these two tips solved my problem.

Doesn’t Tk support JPGs and PNGs out of the box?

If you talk about standard Tcl/Tk only, the answer is “YES”

BTW, I’m not sure I understand what you wrote here. (What does "standard
Tcl/Tk mean?)

4

Hidetoshi NAGAI wrote:

From: Albert S. [email protected]

BTW […] what does “standard Tcl/Tk” mean?

I said it as “Tcl/Tk with no extension”.

As you know, Ruby/Tk uses Tcl/Tk libraries.
It means that functions supported by your Ruby/Tk depend on your
Tcl/Tk on your environment.
[…]
Ruby/Tk can use almost all of Tcl/Tk extensions.
For some of them, Ruby/Tk has wrapper libraries (“tkextlib/*”).
For others, although there are no wrapper libraries, Ruby/Tk can call
functions of those extensions directly (by “Tk.tk_call” method) […]

Thank you for the thorough explanation!

(It’s a pity we don’t have a wiki to collect TK-related info. I did
search for one.)

5

From: Albert S. [email protected]
Subject: Re: Tk supports only GIF?
Date: Sun, 25 Jan 2009 08:07:29 +0900
Message-ID: [email protected]

If you talk about standard Tcl/Tk only, the answer is “YES”
BTW, I’m not sure I understand what you wrote here. (What does "standard
Tcl/Tk mean?)

I’m sorry about my poor English.
I said it as “Tcl/Tk with no extension”.

As you know, Ruby/Tk uses Tcl/Tk libraries.
It means that functions supported by your Ruby/Tk depend on your
Tcl/Tk on your environment.

When you have no Tcl/Tk extensions on your environment,
Ruby/Tk can use Tcl/Tk’s standard (built-in) widgets and functions only.
Tcl/Tk’s “photo” manual describes “At present, only GIF and PPM/PGM
formats are supported”.
Tcl/Tk’s “Img” extension library (loadable module) adds support for
some other image formats to Tcl/Tk.
And then, Ruby/Tk can treat image formats supported by “Img” extension.

Ruby/Tk can use almost all of Tcl/Tk extensions.
For some of them, Ruby/Tk has wrapper libraries (“tkextlib/*”).
For others, although there are no wrapper libraries, Ruby/Tk can call
functions of those extensions directly (by “Tk.tk_call” method),
I think that it is not so difficult to write a wrapper library for
such a extension.

6

Albert S. wrote:

For some of them, Ruby/Tk has wrapper libraries (“tkextlib/*”).
For others, although there are no wrapper libraries, Ruby/Tk can call
functions of those extensions directly (by “Tk.tk_call” method) […]

Thank you for the thorough explanation!

(It’s a pity we don’t have a wiki to collect TK-related info. I did
search for one.)

The Tcl community itself has an excellent wiki:

While there isn’t much Ruby-specific content there, there is a huge
amount of information about Tk.