Java2D: if statement doesn`t work with java.awt.Color

Question

I have a getPixelColour function:

Color getPixelColor(int x, int y) {
    if(mazeImage == null) System.out.println(":(");
    int pixel = mazeImage.getRGB(x, y);
    int  red = (pixel & 0x00ff0000) >> 16;
    int  green = (pixel & 0x0000ff00) >> 8;
    int  blue = pixel & 0x000000ff;
    return new Color(red,green,blue);
}

For example a pixel is black, and System.out.println(getPixelColor(x,y) + " " + Color.BLACK); writes java.awt.Color[r=0,g=0,b=0] java.awt.Color[r=0,g=0,b=0]

But getPixelColor(x,y) == Color.BLACK returns false. What's wrong with it?

If you found any of the below answers helpful you should accept one. As you post more questions members will be reluctant to help you unless you accept useful answers. — darrengorman, Apr 07 '12 at 13:26

score 4 · Accepted Answer · answered Apr 07 '12 at 11:26

4

You are comparing two different Color objects which will return false (i.e., two different objects at different memory locations).

If you wish to properly compare them, use equals():

getPixelColor(x, y).equals(Color.BLACK);

answered Apr 07 '12 at 11:26

Simeon Visser

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score 4 · Answer 2 · answered Apr 07 '12 at 11:29

4

Instead of using getPixelColor(x, y) == Color.BLACK try Color.BLACK.equals(getPixelColor(x, y))

You should also read up on the equals method in Java and when it is appropriate to use it vs. the == operator.

answered Apr 07 '12 at 11:29

darrengorman

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score 2 · Answer 3 · answered Apr 07 '12 at 11:26

If you do

getPixelColor(x,y).equals(Color.BLACK);

I'm sure you will get the result you expect.

The == operator in java is reference equality, and since getPixelColor() returns a new instance of Color it'll never == to Color.BLACK as this a static reference to another instance that happens to be the colour black.

score 2 · Answer 4 · edited May 23 '17 at 12:20

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Color is an object and == compares not the contents of the objects but the instances. So there can be several Color objects containing the RGB values (0,0,0).

You want to compare with col1.equals(col2).

You might look around this site and find plenty of other questions regaring == and equals. As an example:

Java String.equals versus ==

edited May 23 '17 at 12:20

Community

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answered Apr 07 '12 at 11:27

A.H.

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Java2D: if statement doesn`t work with java.awt.Color

4 Answers4