android - how to convert rgb color to int in java

Question

Paint.setColor is expecting an integer. But what I have is a Color object. I don't see a color.getIntValue() in Java? So how do I do that? What I want is something like

public Something myMethod(Color rgb){
    myPaint.setColor(rgb.getIntValue());
    ...
}

Correction: android.graphics.Color; I thought having android as one of the tags would be enough. But apparently not.

Answer 1

First of all, android.graphics.Color is a class thats composed of only static methods. How and why did you create a new android.graphics.Color object? (This is completely useless and the object itself stores no data)

But anyways... I'm going to assume your using some object that actually stores data...

A integer is composed of 4 bytes (in java). Looking at the function getRGB() from the standard java Color object we can see java maps each color to one byte of the integer in the order ARGB (Alpha-Red-Green-Blue). We can replicate this behavior with a custom method as follows:

public int getIntFromColor(int Red, int Green, int Blue){
    Red = (Red << 16) & 0x00FF0000; //Shift red 16-bits and mask out other stuff
    Green = (Green << 8) & 0x0000FF00; //Shift Green 8-bits and mask out other stuff
    Blue = Blue & 0x000000FF; //Mask out anything not blue.

    return 0xFF000000 | Red | Green | Blue; //0xFF000000 for 100% Alpha. Bitwise OR everything together.
}

This assumes you can somehow retrieve the individual red, green and blue colour components and that all the values you passed in for the colours are 0-255.

If your RGB values are in form of a float percentage between 0 and 1 consider the following method:

public int getIntFromColor(float Red, float Green, float Blue){
    int R = Math.round(255 * Red);
    int G = Math.round(255 * Green);
    int B = Math.round(255 * Blue);

    R = (R << 16) & 0x00FF0000;
    G = (G << 8) & 0x0000FF00;
    B = B & 0x000000FF;

    return 0xFF000000 | R | G | B;
}

As others have stated, if you're using a standard java object, just use getRGB();

If you decide to use the android color class properly you can also do:

int RGB = android.graphics.Color.argb(255, Red, Green, Blue); //Where Red, Green, Blue are the RGB components. The number 255 is for 100% Alpha

or

int RGB = android.graphics.Color.rgb(Red, Green, Blue); //Where Red, Green, Blue are the RGB components.

as others have stated... (Second function assumes 100% alpha)

Both methods basically do the same thing as the first method created above.