On Friday 22 February 2002 10:56 am, Jean-Marc Lasgouttes wrote:
> >>>>> "Angus" == Angus Leeming <[EMAIL PROTECTED]> writes:
>
> >> Another question: why do we need grayscale/mono rendering?
> >> Shouldn't we just display the figure as well as the display
> >> permits? This seems very complicated for a small gain...
>
> Angus> Because people ask for it? Anyway, it's about 40 lines of code.
>
> OK, if it is so short, we can handle that. And how do you make sure
> that we limit the number of colors on 8bits display? Do the xpms have
> a common palette?
No, I have done nothing like that. I suspect that is what John was talking
about with XpmAllocCloseCloseColors, but I'm not going to investigate further
as all woks fine on my TrueColor display.
I have simply given the pixmap an m_color and g_color array to go with it's
c_color one.
if (attrib.color_key == XPM_MONO) {
XpmColor * table = xpm_image_->colorTable;
for (int i = 0; i < xpm_image_->ncolors; ++i) {
// If the c_color is defined and the equivalent
// monochrome one is not, then define it.
if (table[i].c_color && !table[i].m_color) {
table[i].m_color =
mapcolor(table[i].c_color, false);
}
}
}
where
// Given a string of the form #ff0571 create a string for the appropriate
// grayscale or monochrome color.
char * mapcolor(char * color, bool toGray)
{
if (!color)
return 0;
Display * display = GUIRunTime::x11Display();
Colormap cmap = GUIRunTime::x11Colormap();
XColor xcol, ccol;
if (XLookupColor(display, cmap, color, &xcol, &ccol) == 0)
// Fail gracefully in the color is called "none".
return 0;
// Note that X stores the RGB values in the range 0 - 65535
// whilst we require them in the range 0 - 255.
int const r = xcol.red / 256;
int const g = xcol.green / 256;
int const b = xcol.blue / 256;
// This gives a good match to a human's RGB to luminance conversion.
// (From xv's Postscript code --- Mike Ressler.)
int mapped_color = (0.32 * r) + (0.5 * g) + (0.18 * b);
if (!toGray) // monochrome
mapped_color = (mapped_color < 128) ? 0 : 255;
ostringstream ostr;
ostr << "#" << std::setbase(16) << std::setfill('0')
<< std::setw(2) << mapped_color
<< std::setw(2) << mapped_color
<< std::setw(2) << mapped_color;
// This string is going into an XpmImage struct, so create a copy that
// libXPM can free successfully.
string str = ostr.str();
char * result = (char *)malloc(str.size()+1); // don't forget '\0'
strcpy(result, str.c_str());
return result;
}
