Re: Pixbuf stuff (rather long)

[NotZed <zucchi zedzone mmc com au>]

> 
> hi, 
> 
> today, i looked at libart code : here are my questions
> 
> 1) is there any documentation on libart (except the sources) ?

According to the api doc status - no.

> 2) there has been some discussion lately on the gnome-canvas-image widget 
> which used imlib and which is beeing ported to pixbuf... I don't realy 
> understand this.

Imlib has many problems.

> Let me know if i am wrong: pixbuf is a generic pixmap buffer (it is some 
> generic data structure). Pixbuf may be used for allmost any kind of pixmap 
> data: with alpha, without alpha... and libart strenght is that it aplies all 
> its transformations on pixbuf, the generic pixmap buffer. That way, you get 
> these transformations on both alpha/non alpha data which can then be 
> displayed. Question: how is a pixbuf displayed ? i mean, is htere support in 
> libart to display pixbufs or is libart just a library which handles these 
> things without actually displaying them ? If libart does not display things, 
> then the gnome-canvas-image widget is there for this. This, makes sense to me.

Libart does not display these things.  gdk_rgb includes routines to 
perform the image conversion to display format (and very fast).

> But, (yes, sorry :) ) if i am not wrong, the gnome-canvas proceeds as 
> follows: let's imagine i have a jpeg image. i load it using imlib which 
> generates some kind of gdk_imlib_pixmap (or something in the like), then i 
> convert this milib data structure to a pixbuf, then i use libart to apply 
> transformations. Last, i display the pixbuf.

For one, imlib doesn't support proper alpha.  So for example, for png
you may have just lost this information.

> Finaly, we are getting to The 2nd question: i hear thses people talking about 
> getting rid of imlib. but right now, it is impossible because imlib is used 
> to load the file content into memory. So, i assume there exist some new 
> library which does nothing but reading files and generating brand new pixbuf 
> buffers . If so, where can i find it ?

gdk-pixbuf is the name of the module.  I'm not sure how stable
it is at present (in terms of functionality, not reliability).

This provides the 'final' missing bit on your mind ... it is the loader
and helper api for loading, transforming and (I believe) displaying
such images.

 Michael