/**
* Clever contrast function
*
* It will try to adjust the foreground color such that it contrasts well with the background
* It won't modify the hue of fg unless absolutely necessary
* @return the adjusted form of fg
*/
QColor
ensureContrast( const QColor &bg, const QColor &fg, uint _amount = 150 )
{
class OutputOnExit {
public:
OutputOnExit( const QColor &color ) : c( color ) {}
~OutputOnExit() { int h,s,v; c.getHsv( &h, &s, &v ); }
private:
const QColor &c;
};
// hack so I don't have to cast everywhere
#define amount static_cast<int>(_amount)
// #define STAMP debug() << (QValueList<int>() << fh << fs << fv);
// #define STAMP1( string ) debug() << string << ": " << (QValueList<int>() << fh << fs << fv);
// #define STAMP2( string, value ) debug() << string << "=" << value << ": " << (QValueList<int>() << fh << fs << fv);
OutputOnExit allocateOnTheStack( fg );
int bh, bs, bv;
int fh, fs, fv;
bg.getHsv( &bh, &bs, &bv );
fg.getHsv( &fh, &fs, &fv );
int dv = abs( bv - fv );
// STAMP2( "DV", dv );
// value is the best measure of contrast
// if there is enough difference in value already, return fg unchanged
if( dv > amount )
return fg;
int ds = abs( bs - fs );
// STAMP2( "DS", ds );
// saturation is good enough too. But not as good. TODO adapt this a little
if( ds > amount )
return fg;
int dh = abs( bh - fh );
// STAMP2( "DH", dh );
if( dh > 120 ) {
// a third of the colour wheel automatically guarentees contrast
// but only if the values are high enough and saturations significant enough
// to allow the colours to be visible and not be shades of grey or black
// check the saturation for the two colours is sufficient that hue alone can
// provide sufficient contrast
if( ds > amount / 2 && (bs > 125 && fs > 125) )
// STAMP1( "Sufficient saturation difference, and hues are compliemtary" );
return fg;
else if( dv > amount / 2 && (bv > 125 && fv > 125) )
// STAMP1( "Sufficient value difference, and hues are compliemtary" );
return fg;
// STAMP1( "Hues are complimentary but we must modify the value or saturation of the contrasting colour" );
//but either the colours are two desaturated, or too dark
//so we need to adjust the system, although not as much
///_amount /= 2;
}
if( fs < 50 && ds < 40 ) {
// low saturation on a low saturation is sad
const int tmp = 50 - fs;
fs = 50;
if( amount > tmp )
_amount -= tmp;
else
_amount = 0;
}
// test that there is available value to honor our contrast requirement
if( 255 - dv < amount )
{
// we have to modify the value and saturation of fg
//adjustToLimits( bv, fv, amount );
// STAMP
// see if we need to adjust the saturation
if( amount > 0 )
adjustToLimits( bs, fs, _amount );
// STAMP
// see if we need to adjust the hue
if( amount > 0 )
fh += amount; // cycles around;
// STAMP
return QColor::fromHsv( fh, fs, fv );
}
// STAMP
if( fv > bv && bv > amount )
return QColor::fromHsv( fh, fs, bv - amount );
// STAMP
if( fv < bv && fv > amount )
return QColor::fromHsv( fh, fs, fv - amount );
// STAMP
if( fv > bv && (255 - fv > amount) )
return QColor::fromHsv( fh, fs, fv + amount );
// STAMP
if( fv < bv && (255 - bv > amount ) )
return QColor::fromHsv( fh, fs, bv + amount );
// STAMP
// debug() << "Something went wrong!\n";
return Qt::blue;
#undef amount
// #undef STAMP
}
/**
* Clever contrast function
*
* It will try to adjust the foreground color such that it contrasts well with
*the background
* It won't modify the hue of fg unless absolutely necessary
* @return the adjusted form of fg
*/
QColor ensureContrast(const QColor& bg, const QColor& fg, uint _amount = 150) {
class OutputOnExit {
public:
explicit OutputOnExit(const QColor& color) : c(color) {}
~OutputOnExit() {
int h, s, v;
c.getHsv(&h, &s, &v);
}
private:
const QColor& c;
};
OutputOnExit allocateOnTheStack(fg);
int bh, bs, bv;
int fh, fs, fv;
bg.getHsv(&bh, &bs, &bv);
fg.getHsv(&fh, &fs, &fv);
int dv = abs(bv - fv);
// value is the best measure of contrast
// if there is enough difference in value already, return fg unchanged
if (dv > static_cast<int>(_amount)) return fg;
int ds = abs(bs - fs);
// saturation is good enough too. But not as good. TODO adapt this a little
if (ds > static_cast<int>(_amount)) return fg;
int dh = abs(bh - fh);
if (dh > 120) {
// a third of the colour wheel automatically guarentees contrast
// but only if the values are high enough and saturations significant enough
// to allow the colours to be visible and not be shades of grey or black
// check the saturation for the two colours is sufficient that hue alone can
// provide sufficient contrast
if (ds > static_cast<int>(_amount) / 2 && (bs > 125 && fs > 125))
return fg;
else if (dv > static_cast<int>(_amount) / 2 && (bv > 125 && fv > 125))
return fg;
}
if (fs < 50 && ds < 40) {
// low saturation on a low saturation is sad
const int tmp = 50 - fs;
fs = 50;
if (static_cast<int>(_amount) > tmp)
_amount -= tmp;
else
_amount = 0;
}
// test that there is available value to honor our contrast requirement
if (255 - dv < static_cast<int>(_amount)) {
// we have to modify the value and saturation of fg
// adjustToLimits( bv, fv, amount );
// see if we need to adjust the saturation
if (static_cast<int>(_amount) > 0) adjustToLimits(bs, fs, _amount);
// see if we need to adjust the hue
if (static_cast<int>(_amount) > 0) fh += static_cast<int>(_amount); // cycles around;
return QColor::fromHsv(fh, fs, fv);
}
if (fv > bv && bv > static_cast<int>(_amount))
return QColor::fromHsv(fh, fs, bv - static_cast<int>(_amount));
if (fv < bv && fv > static_cast<int>(_amount))
return QColor::fromHsv(fh, fs, fv - static_cast<int>(_amount));
if (fv > bv && (255 - fv > static_cast<int>(_amount)))
return QColor::fromHsv(fh, fs, fv + static_cast<int>(_amount));
if (fv < bv && (255 - bv > static_cast<int>(_amount)))
return QColor::fromHsv(fh, fs, bv + static_cast<int>(_amount));
return Qt::blue;
}
