Generate n colors between two colors

问题

I'm trying to write function, which can generate colors between two colors based on a given value. An example would explain it better..

Input ..

X : 1
Y : 0.5
Z : 0

The user gives any set of color:value pairs, then enters a number(say 0.75). I have to then generate color which is a blend of Y and Z in proportion(based on the their values and the input value). I was thinking of the following approach.

Find the colors which surround the value, for 0.75 it will be 0.5 and 1.
Mix those two colors somehow, based on the value and generate new colors.

I'm completely lost, as how to generate colors and are there any libraries for this.

UPDATE: It is part of a bigger project I'm working on. Lets say we have ..

1 : X
0 : Y

and the user inputs, 0.25

I would like to have something..

(X*0.25 + Y*0.75)

as it's more near to Y, that's why the higher proportion. If the user inputs, 0.5.. the output should be

(X*0.5 + Y*0.5)

and so on. I have no idea how to do this with RGB colors.

P.S: The questions is not specific to language, but I'm doing this in Java.

回答1:

You have to blend each color channel (red, green and blue) seperately like this:

Color x,y; //set by you
float blending;//set by you

float inverse_blending = 1 - blending;

float red =   x.getRed()   * blending   +   y.getRed()   * inverse_blending;
float green = x.getGreen() * blending   +   y.getGreen() * inverse_blending;
float blue =  x.getBlue()  * blending   +   y.getBlue()  * inverse_blending;

//note that if i pass float values they have to be in the range of 0.0-1.0 
//and not in 0-255 like the ones i get returned by the getters.
Color blended = new Color (red / 255, green / 255, blue / 255);

So far for the color example. Generally if you want a linear interpolation between two values you have to do the following:

var firstValue;
var secondValue;
var interpolation;

var interpolated =  firstValue * interpolation + 
                   secondValue * (1 - interpolation);

But since you have Color-Objects in your case, you cannot interpolate the whole object in one step, you have to interpolate each relevant value on its own. Eventually you have to interpolate the alpha-channel as well, don´t know that, since you didn´t mention it, but for completeness i include it in this answer.

回答2:

A color is a point in a three-dimensional space. The exact coordinates used depend on what's called a "color space", of which there are several: RGB, HSV, and so on. So to compute a color in between two given colors, get those two colors in the same color space, and compute a third point between those two along the line in 3d-space between them.

The simplest way to do this would be simply to do a linear interpolation for each of the three values of the colorspace (R, G, and B, for example). But there's a further complication that the coordinate values are often not linear, so you have to linearize them first (for example, TV colors are exponential with a lambda of about 2.2). Depending on your application, incorrectly assuming linearity might work OK anyway, especially if the starting colors are already close.

(As mentioned by luk2302, add a fourth coordinate for alpha if necessary).

回答3:

You could use Java.awt.color by doing somting like this:

public Color mixColors(Color color1, Color color2, double percent){
      double inverse_percent = 1.0 - percent;
      int redPart = (int) (color1.getRed()*percent + color2.getRed()*inverse_percent);
      int greenPart = (int) (color1.getGreen()*percent + color2.getGreen()*inverse_percent);
      int bluePart = (int) (color1.getBlue()*percent + color2.getBlue()*inverse_percent);
      return new Color(redPart, greenPart, bluePart);
}

来源：https://stackoverflow.com/questions/17544157/generate-n-colors-between-two-colors

标签

java

algorithm

colors

rgb