Re: 100 Different Colors

[Kevin DeKorte <kdekorte yahoo com>]

You are dividing first and getting an int 0 * G_MAXUINT16

in the line

 c.green = i/99 * G_MAXUINT16;

Multiply first and then divide. you might need a long int tmp to hold the 
value prior to assigning to c.green. By dividing first you basically are 
doing a multiply by 0 and that is why it is 0 until i = 99 which when divided 
by 99 will give you 1. Then multiple 1 x G_MAXUINT16 will give G_MAXUINT16 or 
65535. 

So the next line might be better.

 c.green = (i * G_MAXUINT16) / 99;

Kevin

On Tuesday 21 June 2005 01:33 pm, Lola Smith wrote:
> > Before your call to gdk_set_rgb_fg_color, do a
> > g_print on the values of
> > c.red, c.blue, c.green, and i.  You may be surprised
> > at what you see.
>
> You're right. They're all the same thoughout the loop.
> red = 65535, blue = 0, green = 0, except at the very
> end green = 65535 (hence the yellow color). I figured
> this is because they are integers, not doubles.
>
> So, how is it possible to change the colors inside the
> loop?
>
> Sorry, I'm pretty clueless right now... :-(
> Any help is appreciated!
>
> > > -----Original Message-----
> > > From: gtk-app-devel-list-bounces gnome org
> >
> > [mailto:gtk-app-devel-list-
> >
> > > bounces gnome org] On Behalf Of Lola Smith
> > > Sent: Tuesday, June 21, 2005 11:10 AM
> > > To: gtk-app-devel-list gnome org
> > > Subject: Re: 100 Different Colors
> > >
> > > Jan-Marek, thanks for your response.
> > >
> > > I tried this:
> > > > for (i=0; i<100; i++) {
> > > >   c.pixel = 0;
> > > >   c.red   = G_MAXUINT16;
> > > >   c.blue  = (i % 33 / 99) * G_MAXUINT16;
> > > >   c.green = i/99 * G_MAXUINT16;
> > > >   gdk_gc_set_rgb_fg_color( gc, &c );
> > > >   gdk_draw_rectangle (widget->window, gc, TRUE,
> > >
> > > i*15,
> > >
> > > >     0, 11, 11);
> > > > }
> > >
> > > But all the squares are red now, with the
> >
> > exception of
> >
> > > the last one (100th), which is yellow.
> > > Do I have to change the value of c.red inside the
> >
> > for
> >
> > > loop as well? Maybe something related to i?
> > >
> > > Btw, I am using gtk version 2.2, which didn't have
> > > G_MAXUINT16, so I defined it like:
> > >
> > > #define G_MAXUINT16 ((guint16) 0xffff)
> > >
> > > Can someone help? Thaaank you!
> > >
> > > --- Jan-Marek Glogowski <glogow fbihome de> wrote:
> > > > Hi
> > > >
> > > > > I need to create 100 little squares and each
> >
> > of
> >
> > > > them
> > > >
> > > > > has to be a different color. They can't just
> >
> > be a
> >
> > > > > random color: they have to follow the colors
> >
> > of
> >
> > > > the
> > > >
> > > > > standard color spectrum/palette. For example,
> >
> > the
> >
> > > > > first one is dark blue, then lighter blue, ...
> >
> > ,
> >
> > > > > green, ... , red.
> > > >
> > > > Std. color spectrum? Maybe like the circle in
> >
> > the
> >
> > > > GtkColorSelectionDialog?
> > > >
> > > > Algo:
> > > > r = max, g = 0, b = 0
> > > > r = max , g = max, b = 0
> > > > r = 0, g = max, b = 0
> > > > r = 0, g = max, b = max
> > > > r = 0, g = 0, b = max
> > > > r = max, g = 0, b = max
> > > > back to step 1
> > > >
> > > > See GtkColorSelection source
> > > >
> > > > From the GDK Manual:
> > > >
> > > > gdk_gc_set_rgb_fg_color () - set the foreground
> > > > color of a GC using an
> > > > unallocated color.
> > > >
> > > > GdkColor - red, green, blue ... is a value
> >
> > between 0
> >
> > > > and 65535, with 65535
> > > > indicating full intensitiy.
> > > >
> > > > GdkGC *gc;
> > > > GdkColor c;
> > > >
> > > > gc = gdk_gc_new (widget->window);
> > > >
> > > > for (i=0; i<100; i++) {
> > > >   c.pixel = 0;
> > > >   c.red   = G_MAXUINT16;
> > > >   c.blue  = (i % 33 / 99) * G_MAXUINT16;
> > > >   c.green = i/99 * G_MAXUINT16;
> > > >   gdk_gc_set_rgb_fg_color( gc, &c );
> > > >   gdk_draw_rectangle (widget->window, gc, TRUE,
> > > > i*15,
> > > >     0, 11, 11);
> > > > }
> > > >
> > > > HTH
> > > >
> > > > Jan-Marek
> >
> > ____________________________________________________
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