Re: How to store Gdk::Pixbuf pixels into std::string objects

[Rob Pearce <list gtkmm flitspace org uk>]

(Oops, sent from wrong address first time)

On 24/02/15 12:28, Glus Xof wrote:
> I need your help...
>
> I insist that maybe it's not an specifically Gtkmm question... but you
> may know better how it's done, the library...

It's not even related to the library, really. The issue here is a basic
C++ issue.

> Gdk::Pixbuf::get_pixels()... returns a guint8 (const unsigned char)
> pointer. So,
>
> 1) Which is the best way to build an std::string object containing the
> data of the buffer (the pixels)... ?

The best way, as you've been told, is to "Not do that". It's the Wrong
Thing To Do.

<snip>

> Why std::vector(s) should be used, here ?

Because a std::vector<guint8> is the correct container for binary data.
A std::string is a container for a string, which is text, and which can
be expected to obey rules for text, such as not containing null
characters because they terminate C-strings.

What benefit do you expect to obtain from using std::string? It can't be
any of the special methods for handling text, because you're not
populating it with text. And that only leaves base methods common to all
std:: container classes.

So use std::vector

> ==
>
> Once an std::string object created... and from this object...
>
> 2) Which is the best way to convert it back to guint8 (const unsigned
> char) pointer, in order to pass it as first argument to
> Gdk::Pixbuf::create_from_data() ?
One of the nice things about a std::vector<x> is that it provides a
method to directly expose the underlying C-style array of x - in your
case the guint8* that you want.


> I'd like to know how to realize these two steps... even if building
> std::string objects sounds a little silly or strange... I wonder... is
> it possible ?
It sounds silly, strange, ill-thought-out and inappropriate. Why do you
have this fixation with doing things the wrong way when the right way is
easier?

HTH
Rob