Re: Converting a GdkPixmap to a rgb_buf

[Rob Alblas <r alblas demon nl>]

Antony Stace wrote:

> Hi Folks
>
> How can I convert a GdkPixmap to the correct format that
> gdk_draw_rgb_image() accepts as input.  It is a matrix of type guchar,
> but I don't know how to make this matrix.

I think you can't. You have to fill the guchar array yourself
(pixel-by-pixel). See the docs, gdk-gdkrgb.html.
This problem is related to the "How to add strings using GdkRGB" problem
I sent 2 times, with little response.
I think it is just not possible; you have to do everything youself to
fill the guchar array with what you want.
I have made functions myself to set a pixel (see end of this mail), a
line and a string (though the last one I am not very happy with, because
it uses just 1 built-in font).


void draw_rgbpoint(guchar *rgbbuf,int width,
                                      GdkColor *clr,
                                       int x,int y)
{
  int yoffset=y*width*3;
  rgbbuf[yoffset+3*x+0]=clr->red;
  rgbbuf[yoffset+3*x+1]=clr->green;
  rgbbuf[yoffset+3*x+2]=clr->blue;
}


Rob.