2015-02-23 23:05 GMT+01:00 Glus Xof <gtg...@gmail.com>:
>
>
> 2015-02-23 22:21 GMT+01:00 Markus Kolb <markus.kolb+gt...@tower-net.de>:
>>
>> Am 2015-02-23 21:40, schrieb Glus Xof:
>>>
>>> Hi guys,
>>>
>>> Before anything, I admit that probably my question is not an specifically
>>> Gtkmm question... but nevertheless I think you may know how Gdk::Pixbuf
>>> is
>>> done...
>>>
>>> Having the following,
>>>
>>> Glib::RefPtr<Gdk::Pixbuf> ref_orig = Gdk::Pixbuf::create_from_file
>>> ("./file.png");
>>>
>>> I'm trying to temporary store (because I need so) the image data into a
>>> std::string object. It seems that get_pixels() could solve the problem,
>>> getting a pointer of type guint8.
>>
>>
>> Seems that gdkmm is not up-to-date here.
>> gdk uses a guchar*. But this shouldn't be a problem.
>
>
>>>
>>> So, I wrote as follows,
>>>
>>> std::string image_pixels (reinterpret_cast<const char
>>> *>(ref_orig->get_pixels()), ref_orig->get_rowstride());
>>
>>
>> I think this does not what you expect.
>>
>>
>> https://developer.gnome.org/gdk-pixbuf/stable/gdk-pixbuf-The-GdkPixbuf-Structure.html#gdk-pixbuf-get-rowstride
>>
>> See also the part below the description headline.
>>
>> Maybe you should use gsize Gdk::Pixbuf::get_byte_length()
>> because
>> https://developer.gnome.org/gdk-pixbuf/stable/gdk-pixbuf-The-GdkPixbuf-Structure.html#gdk-pixbuf-get-pixels-with-length
>> is missing.
>>
>> I hope it will help you.
>>
>> But think about the std::string. Big ? ;-)
>>
>
> According to Yann & Markus' comments, I remake my code as follows,
>
> Glib::RefPtr<Gdk::Pixbuf> ref_orig = Gdk::Pixbuf::create_from_file
> ("./file.png");
>
> // Glib::ustring::c_str() or data() allows me to get an std::string
> object...
>
> Glib::ustring image_pixels (
> reinterpret_cast<const char *>(ref_orig->get_pixels()),
> ref_orig->get_byte_length());
I think you wanted to use std::string here instead of Glib::ustring.
Glib::ustring expects utf8 strings, not some random binary data.
Especially it does not like embedded zeros. The Glib::ustring
constructor calls utf8_byte_offset
(https://git.gnome.org/browse/glibmm/tree/glib/glibmm/ustring.cc#n60)
returns std::string::npos when it encounters embedded zero. And that
thing is passed to std::string constructor which throws the exception,
because npos is a -1 cast to size_type.
Anyway, I'd recommend rather using std::vector instead.
>
> Glib::RefPtr<Gdk::Pixbuf> ref_dest =
> Gdk::Pixbuf::create_from_data (
> reinterpret_cast<const guint8*>(image_pixels.data()),
> Gdk::COLORSPACE_RGB,
> ref_orig->get_has_alpha(), ref_orig->get_bits_per_sample(),
> ref_orig->get_width(), ref_orig->get_height(),
> ref_orig->get_rowstride());
>
> But, at runtime I get a lenght error exception,
>
> terminate called after throwing an instance of 'std::length_error'
> what(): basic_string::_S_create
>
> Could help ?
>
> Glus
>
>
>
>
>
>>
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