From: Sergio Masci (sergio@titan.demon.co.uk)
Date: Sun 09 Jul 2000 - 23:45:13 IDT
> > > > On Sun, 9 Jul 2000, Sergio Masci wrote: > > > > > Before applying the BMP colours to the hardware colour palette (via > > vga_setpalette) try the following mystical incantation - it may help. > > svgalib_red = (bmp_red >> 2) & 0x3f; > > svgalib_green = (bmp_green >> 2) & 0x3f; > > svgalib_blue = (bmp_blue >> 2) & 0x3f; > > Thanks. That worked. But why? > > > -pat The individual components (RGB) of a colour palette entry are often stored as 6 bit values (this is hardware dependent and some video cards use a different number of bits but 6 seems to be the most common). These 6 bits correspond to the most significant bits of the colour so you need to align the bmp component with the svgalib component (top bit) before you plug it in. If you do not then you will lose VERY IMPORTANT colour info from some of your colours. Discarding low end info is not as big a problem as long you are consistant. As an experiment try disacarding 4 low end bits instead of 2 i.e. svgalib_x = (bmp_x >> 4) & 0x0f; or even svgalib_x = (bmp_x >> 2) & 0x03c; You still get an infinately better picture than you did before you applied any alignment. Regards Sergio
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