Re: [Linux-fbdev-devel] fb_imageblit()

[Geert U. <ge...@li...>]

On 8 Jan 2003, Antonino Daplas wrote:

> On Wed, 2003-01-08 at 06:23, James Simmons wrote: 
> > > >     
> > > >     If monochrome image data would be packed as well, it could be handled by
> > > >     setting fb_image.fg_color = 1 and fb_image.bg_color = 0 (or vice versa for
> > > >     mono10), and fb_set_logo() becomes simpler as well.
> > > > 
> > > >     If we retain the unpacked data for images, we need some other flag to
> > > >     indicate color expansion. Perhaps setting fb_image.depth to 0?
> > > > 
> > > If we change the contents of the logo data, then it makes sense to pack
> > > the logo data also.  However, if we stick to indices, we might as well
> > > retain the "unpacked" 8-bit format.  I think setting fb_image.depth to 0
> > > to mean color expansion is more appropriate. Drivers that will need
> > > trivial changing would be tgafb, i810fb, rivafb, tdfxfb, atyfb, vga16fb
> > > and of course cfb_imgblt.c, softcursor.c and fbcon.c.
> > 
> > The requirement I made of imageblit was to always use packed data. What 
> > the indices approach was to to always use a struct fb_cmap. This way it 
> > didn't matter if used a pseudocolor mode or a directcolor mode.
>  
> I've thought of that also, packing the data according to the pixel depth.  
> However, this will be very inefficient since image blitting
> will go like this: 
> 
> a. Prepare logo data so each pixel of data is in directcolor format (if
> we will use the cmap), so depth corresponds to framebuffer depth, and
> data is packed. 
> 
> b. Pass the structure to cfb_imageblit. 
> 
> c. In cfb_imageblit, unpack the logo data: 
> 
> d. Get each color component from the cmap data. 
> 
> e. Recreate pixel data based on var.[color].offset and
> var.[color].length. 
> 
> f. Write the pixel data in packed form to the framebuffer. 
> 
> Whereas, with the current approach: 
> 
> a. Prepare logo data such that each pixel corresponds to one byte. 
> 
> b. Pass the structure to cfb_imageblit. 
> 
> c. Read color information from pseudopalette if directcolor/truecolor. 

Hoever, pseudopalette has entries for the first 16 colors only!
Hence you are limited to the 16 color for directcolor/truecolor modes.

> d. Write the pixel data in packed form to the framebuffer. 

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@li...

In personal conversations with technical people, I call myself a hacker. But
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							    -- Linus Torvalds