Re: [Linux-fbdev-devel] Re: Problem with current fb_get_color_depth function

On Mon, 1 Nov 2004, Joshua Kwan wrote:

[ long overdue follow-up ]

On Mon, Oct 11, 2004 at 08:33:10AM +0800, Antonino A. Daplas wrote:

quoted

So, linux_logo_224 cannot be drawn when visual is directcolor at RGB555 or
RGB565 because the logo clut requirements exceeds the hardware clut
capability. You need to use a logo image with a lower depth such as the
16-color logo, linux_logo_16.

This is weird, because removing that conditional from fb_get_color_depth
allows a 224-color logo to show correctly on my Radeon framebuffer, in
full color.

Otherwise, it is dithered to kingdom come and mostly appears all orange
and black.

You may be right conceptually, but the fact of the matter is that this
is a regression because 224-color logos work perfectly with the old
fb_get_color_depth. So what is the real problem?

quoted

In short, fb_get_color_depth() and radeonfb both do the correct thing, but
you need a logo with a lower color depth. Or choose RGB888 or higher, or
set the visual to truecolor.

What does that last sentence mean? -- I have no idea...

In directcolor mode, the pixel color is:

    (clut.red[r], clut.green[g], clut.blue[b])

with r, g, and b being the values in the pixel (i.e. they are in the range
0..31 for RGB555, and g in the range 0..63 for RGB565).

In truecolor mode, the pixel color is:

    (r, g, b)

quoted

PS: Note that this behavior is the same as 2.4 behavior (224-color logo is
only chosen if directcolor and bpp >= 24).  It might have worked before, and
this is probably due to the directcolor clut being ramped to truecolor
values. However, the correct solution is to use a 16-color logo.

Oh, I see, I didn't read this before.

Well, 16-color logos being used when 224-color ones work perfectly
enough 99% of the time is pretty bad aesthetically, if you ask me.

It's very strange that it did work before, since there's no way to set up the
32-entry CLUT (of which BTW the first 16 colors are the standard console
colors) for any random 224-color image in RGB555 mode.

In RGB888 mode (24-bit color) it's possible though, since the CLUT has 256
entries.

Can you show us a screenshot (e.g. using fbgrab) of the old behavior?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds