void tst_QColor::convertTo()
{
QColor color(Qt::black);
QColor rgb = color.convertTo(QColor::Rgb);
QVERIFY(rgb.spec() == QColor::Rgb);
QColor hsv = color.convertTo(QColor::Hsv);
QVERIFY(hsv.spec() == QColor::Hsv);
QColor cmyk = color.convertTo(QColor::Cmyk);
QVERIFY(cmyk.spec() == QColor::Cmyk);
QColor hsl = color.convertTo(QColor::Hsl);
QVERIFY(hsl.spec() == QColor::Hsl);
QColor invalid = color.convertTo(QColor::Invalid);
QVERIFY(invalid.spec() == QColor::Invalid);
DEPENDS_ON(toRgb());
DEPENDS_ON(toHsv());
DEPENDS_ON(toCmyk());
DEPENDS_ON(toHsl());
}
void Pixel::convertColorModel(ColorModel model)
{
// When converting between models other then RGB, first convert to RGB then to other model
if (this->model != RGB)
toRgb();
if (model == RGB) return; // Nothing to do
int R = c[0], G = c[1], B = c[2];
double X,Y,Z,L_lab,a_lab,b_lab; // used in several conversions
if (model == YUV) {
// YUV formula
/*double Y, U, V;
Y = 0.299*R + 0.587*G + 0.114*B;
U = 0.492*(B-Y);
V = 0.877*(R-Y);
// Ranges are now Ye[0,1], Ue[-0.436,0.436], Ve[-0.615,0.615]
// Convert to byte:
Y = toByte(Y*256);
U = toByte((U+0.436)*256 / (0.436*2));
V = toByte((V+0.615)*256 / (0.615*2));*/
// The following is equivalent and comes from JPEG standard
int Y = toByte ( 0.299 * R + 0.587 * G + 0.114 * B );
int U = toByte ( 128 - 0.168736 * R - 0.331264 * G + 0.5 * B );
int V = toByte ( 128 + 0.5 * R - 0.418688 * G - 0.081312 * B );
c[0] = Y; c[1] = U; c[2] = V;
return;
}
if (model == YIQ) {
int Y = toByte ( 0.299 * R + 0.587 * G + 0.114 * B );
int I = toByte ( (152 + 0.596 * R - 0.275 * G - 0.321 * B) / 304 * 255 );
int Q = toByte ( (133 + 0.212 * R - 0.523 * G + 0.311 * B) / 266 * 255 );
c[0] = Y; c[1] = I; c[2] = Q;
return;
}
if (model == HSV) {
int H, S, V;
QColor color(R, G, B);
color.getHsv(&H, &S, &V);
H = (H*256)/360; // Rescale to 0-255
if (H==256) H=255;
c[0] = H; c[1] = S; c[2] = V;
return;
}
if (model == HSL) {
int H, S, L;
QColor color(R, G, B);
color.getHsl(&H, &S, &L);
H = (H*256)/360; // Rescale to 0-255
if (H==256) H=255;
c[0] = H; c[1] = S; c[2] = L;
return;
}
if (model == HSI) {
int H, S, I;
QColor color(R, G, B);
color.getHsl(&H, &S, &I);
H = (H*256)/360; // Rescale to 0-255
if (H==256) H=255;
I = (R+G+B)/765; // 765 = 3*255
c[0] = H; c[1] = S; c[2] = I;
return;
}
if (model == IHLS) {
// More perceptually uniform variant of HSL color space
// See: Hanbury and Serra "A 3D-polar coordinate colour representation suitable for image analysis" (2002)
int H, S, L;
QColor color(R, G, B);
color.getHsl(&H, &S, &L);
H = (H*256)/360; // Rescale to 0-255
if (H==256) H=255;
int M=qMax(R,qMax(G,B));
int m=qMin(R,qMin(G,B));
S = M-m;
c[0] = H; c[1] = S; c[2] = L;
return;
}
if (model == HMMD) {
// Color model used in MPEG-7 standard
// See: Manjunath et al. "Color and texture descriptors" (2001)
int H, S, V;
QColor color(R, G, B);
color.getHsv(&H, &S, &V);
H = (H*256)/360; // Rescale to 0-255
if (H==256) H=255;
int M=qMax(R,qMax(G,B));
int m=qMin(R,qMin(G,B));
int D=M-m;
c[0] = H; c[1] = M; c[2] = m; c[3] = D;
return;
}
if (model == HY) {
int H, S, V;
QColor color(R, G, B);
color.getHsv(&H, &S, &V);
H = (H*256)/360; // Rescale to 0-255
if (H==256) H=255;
int Y = toByte ( 0.299 * R + 0.587 * G + 0.114 * B );
c[0] = H; c[1] = Y;
return;
}
if (model == XYZ || model == LAB || model == LUV || model == LCH) {
// Convert RGB to range [0,1]
double r(double(R)/255);
double g(double(G)/255);
double b(double(B)/255);
// We assume that color is sRGB with decoding gamma of 2.2, as customary
// Linearize sRGB
if (r<0.04045) r=r/12.92; else r=pow((r+0.055)/1.055, 2.4);
if (g<0.04045) g=g/12.92; else g=pow((g+0.055)/1.055, 2.4);
if (b<0.04045) b=b/12.92; else b=pow((b+0.055)/1.055, 2.4);
// Convert sRGB to XYZ using transformation matrix
X = 0.4124564 * r + 0.3575761 * g + 0.1804375 * b;
Y = 0.2126729 * r + 0.7151522 * g + 0.0721750 * b;
Z = 0.0193339 * r + 0.1191920 * g + 0.9503041 * b;
}
if (model == XYZ) {
c[0] = toByte(X*255);
c[1] = toByte(Y*255);
c[2] = toByte(Z*255);
return;
}
if (model == LAB || model == LCH) {
// Reference illuminant D65 white point
double Xn = 0.95047;
double Yn = 1;
double Zn = 1.08883;
double D = pow( 6.0 / 29.0, 3 );
double Xfn( X / Xn ), Yfn( Y / Yn ), Zfn( Z / Zn );
if ( Xfn > D ) Xfn = pow(Xfn,1.0/3.0); else Xfn = ( 1.0 / 3.0 ) * pow( (29.0 / 6.0), 2) * Xfn + ( 4.0 / 29.0 );
if ( Yfn > D ) Yfn = pow(Yfn,1.0/3.0); else Yfn = ( 1.0 / 3.0 ) * pow( (29.0 / 6.0), 2) * Yfn + ( 4.0 / 29.0 );
if ( Zfn > D ) Zfn = pow(Zfn,1.0/3.0); else Zfn = ( 1.0 / 3.0 ) * pow( (29.0 / 6.0), 2) * Zfn + ( 4.0 / 29.0 );
L_lab = 116 * Yfn - 16;
a_lab = 500 * (Xfn - Yfn);
b_lab = 200 * (Yfn - Zfn);
}
if (model == LAB) {
// Convert to byte
c[0] = toByte( L_lab * 255 / 100 );
// Actual gamut of RGB in CIE Lab space is [0,100], [-86,98], [-107,94];
c[1] = toByte( (a_lab + 86) * 255 / (86 + 98) );
c[2] = toByte( (b_lab + 107) * 255 / (107 + 94) );
return;
}
if (model == LCH) {
// a and b are in range [-127,128]
a_lab = (a_lab+127) / 255;
b_lab = (b_lab+127) / 255;
double H = atan2(b_lab, a_lab);
double C = sqrt(a_lab*a_lab + b_lab*b_lab);
c[0] = toByte( L_lab * 255 / 100 );
// H is in range [0.092, 1.37]
c[1] = toByte( (H - 0.092) * 199 );
// C is in range [0.533, 1.11]
c[2] = toByte( (C - 0.533) * 440 );
return;
}
if (model == LUV) {
// Reference illuminant D65 white point
double Xn = 0.95047;
double Yn = 1;
double Zn = 1.08883;
double D = pow( 6.0 / 29.0, 3 );
double Yfn( Y / Yn );
if ( Yfn > D ) Yfn = pow(Yfn,1.0/3.0); else Yfn = ( 1.0 / 3.0 ) * pow( (29.0 / 6.0), 2) * Yfn + ( 4.0 / 29.0 );
double Xfn((4*X) / (X + 15*Y + 3*Z));
double Zfn((9*Y) / (X + 15*Y + 3*Z));
double Xref((4*Xn) / (Xn + 15*Yn + 3*Zn));
double Zref((9*Yn) / (Xn + 15*Yn + 3*Zn));
double L = 116 * Yfn - 16;
double u = 13 * L * ( Xfn - Xref );
double v = 13 * L * ( Zfn - Zref );
// Convert to byte
c[0] = toByte( L*255 / 100 );
c[1] = toByte( u + 127 );
c[2] = toByte( v + 127 );
return;
}
if (model == L1L2L3) {
// See: Gevers and Smeulders "Color-based object recognition" (1999)
int d1 = (R-G)*(R-G);
int d2 = (R-B)*(R-B);
int d3 = (G-B)*(G-B);
double l1 = double(d1) / (d1+d2+d3);
double l2 = double(d2) / (d1+d2+d3);
double l3 = double(d3) / (d1+d2+d3);
c[0] = toByte(l1);
c[1] = toByte(l2);
c[2] = toByte(l3);
}
}
