24-bit-per-pixel limit to Gdk RGB ?

[individual <individual mi cl>]

Hi,
On Sunday, February 2, 2003, at 09:57 AM, Roland Smith wrote:

> On Sat, 1 Feb 2003 18:09:48 -0300
> "Individual . ." <individual mi cl> wrote:
>
> > I decided it would be great if I could learn how to plot an image to a
> > window, pixel by pixel. Getting the  image is no problem at all, since
> > I wrote a simple c++ class that uses libpng
> > (<http://pngwriter.sourceforge.net/>).
> > The plotting part is what is holding me up.
> >
> > I have looked at the scribble program that is given as an example, but
> > I must say that the lack of a chapter on drawing_area widgets in the
> > tutorial isn't helping me one bit!
>
> Plotting pixel by pixel is _slow_. It's better to use GdkRGB, e.g. 
> using
> gdk_draw_rgb_image(). What you have to do is read from the png file to 
> a buffer
> containing an array of rgb values. This is then drawn to a drawable. 
> See the
> example in the GDK manual.

After 2 weeks of silence, I'm back. I paused my learning of Gtk and did 
some things in Xlib. Not pretty, as someone said. I got as far as 
XCreateImage, but when I handed it the image data (in 48 bit-per-pixel 
triplets) it spewed out a distorted, flipped and psychedelic version of 
the original image. I tried to find what order it wanted the data in, 
but no luck. I asked on the XFree86-devel list, and got no useful 
answer.

So it's back to Gtk. Yes, having to mess with all colour depths is not 
pretty.

I looked at the API reference, and saw gdk_draw_rgb_image (), but it 
seems to be a 24-bit-per-pixel affair. Even the one with "32" in its 
name only is 32 bits per pixel because of 8 padding bits.

Is there a way to display 48-bit-per-pixel image data? The API 
reference entry for GdkRgbDither states:

"Since GdkRGB currently only handles images with 8 bits per component, 
dithering on 24 bit per pixel displays is a moot point. "

Uh-oh...

I'm looking at gdk_draw_pixbuf () right now, but I don't see anything 
referring to max bit depth.

Thanks in advance for the help and comments.

Paul