希望这是你要找的:
double interpolate( double val, double y0, double x0, double y1, double x1 ) {
return (val-x0)*(y1-y0)/(x1-x0) y0;
}
double blue( double grayscale ) {
if ( grayscale < -0.33 ) return 1.0;
else if ( grayscale < 0.33 ) return interpolate( grayscale, 1.0, -0.33, 0.0, 0.33 );
else return 0.0;
}
double green( double grayscale ) {
if ( grayscale < -1.0 ) return 0.0; // unexpected grayscale value
if ( grayscale < -0.33 ) return interpolate( grayscale, 0.0, -1.0, 1.0, -0.33 );
else if ( grayscale < 0.33 ) return 1.0;
else if ( grayscale <= 1.0 ) return interpolate( grayscale, 1.0, 0.33, 0.0, 1.0 );
else return 1.0; // unexpected grayscale value
}
double red( double grayscale ) {
if ( grayscale < -0.33 ) return 0.0;
else if ( grayscale < 0.33 ) return interpolate( grayscale, 0.0, -0.33, 1.0, 0.33 );
else return 1.0;
}
我不知道如果这个比例是100%相同的图像,你链接,但它应该看起来很相似。
更新
我根据MatLab的Jet重写调色板的描述代码here
double interpolate( double val, double y0, double x0, double y1, double x1 ) {
return (val-x0)*(y1-y0)/(x1-x0) y0;
}
double base( double val ) {
if ( val <= -0.75 ) return 0;
else if ( val <= -0.25 ) return interpolate( val, 0.0, -0.75, 1.0, -0.25 );
else if ( val <= 0.25 ) return 1.0;
else if ( val <= 0.75 ) return interpolate( val, 1.0, 0.25, 0.0, 0.75 );
else return 0.0;
}
double red( double gray ) {
return base( gray - 0.5 );
}
double green( double gray ) {
return base( gray );
}
double blue( double gray ) {
return base( gray 0.5 );
}