Data conversion to Image

[Bob Home <bobstaff snowhill com>]

I have a 2d dimensional grid of 8 bit weather radar data which I need to
display in a gtk_drawing_area. I've succeeded in doing this with the
following code, but I suspect there must be a more efficient way to do
this. Any suggestions would be appreciated.

There are also a few questions in the code that I'd appreciate info on.
GdkColor colmap[]=
{
        // pixel     red        greeen blue
        {0x0000,0x0000,0x0000,0x0000},
        {0x0000,0x0000,0x0000,0xfffff},
                            :
                            :
        {0x0000,0xffff,0x0000,0x0000}
};
// Allocate colors
for(i=0;i<numcolors;i++)
{
    // Generate the pixel value, I thought that
gdk_colormap_alloc_color, was suppposed to do this
    // but it only seems to work if I do it.
    colmap[i].pixel = ((colmap[i].red&0xff00)<8)||
        ((colmap[i].green&0xff00))||
        ((colmap[i].blue>>8));
    // Allocate color map, I'm not clear what this does or why it is
necessary on a 24 bit display, any info
    // would be appreciated.
 gdk_colormap_alloc_color(gdk_window_get_colormap(GTK_WIDGET(draw)->window),&comap[i],FALSE,TRUE);

}

//Plot the image one pixel at a time
for(x=0;x<XSIZE;x++)
    for(y=0;y<YSIZE;y++)
    {
        int col = colorfunc(data[x][y]);        // Select which color
from colmap to use for this pixel
        // Set the foreground color

gdk_gc_set_foreground(style->dark_gc[GTK_STATE_NORMAL],colmap+col);
        // Plot the point

gdk_draw_point(GTK_WIDGET(draw)->window,style->dark_gc[GTK_STATE_NORMAL],x,y);

    }