CODEWITHSUNDEEP
javaimagepixelbufferedimage
Benjamin Spiegel
Benjamin Spiegel

Reputation: 113

How do I test a pixel of a bufferedimage for a certain color in Java

I'm trying to take a screenshot and then look through it for a pixel that has a certain color. Firstly, I tried to just print the color of an image at a certain xy coordinate but I could not even do that. What am I doing wrong?

static int ScreenWidth;
static int ScreenHeight;
static Robot robot;

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    // TODO code application logic 
    callibrateScreenSize();
    findSquares();
    //takeScreenShot();

    try {
        Thread.sleep(1000);
    } catch (Exception e) {
        e.printStackTrace();
    }

}

public static void callibrateScreenSize() {

    try {
        Rectangle captureSize = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());
        ScreenWidth = captureSize.width;
        ScreenHeight = captureSize.height;
        System.out.println("Width is " + ScreenWidth);
        System.out.println("Height is " + ScreenHeight);
    } catch (Exception e) {
        e.printStackTrace();
    }
    //return null;
}

public static BufferedImage takeScreenShot() {
    Rectangle captureSize = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());
    BufferedImage image = robot.createScreenCapture(captureSize);
    return image;
}

public static void findSquares() {
    System.out.println(takeScreenShot().getRGB(5,5));
}

Thanks!

Upvotes: 0

Views: 1939

Answers (2)

S. Roughani
S. Roughani

Reputation: 9

Here's something I wrote a while ago using the Robot class. It returns an array of the screen wherever the screen is white, it was not very computationally expensive for my application, but I found probing the values individually using robot was. At first I didn't even read your question, but looking back, I think this will help you A LOT. Good luck. And then I saw the original post date...

public boolean[][] raster() throws AWTException, IOException{
   boolean[][] filled= new boolean[720][480];
  BufferedImage image = new Robot().createScreenCapture(new Rectangle(0,0,720,480));
//accepts (xCoord,yCoord, width, height) of screen
    for (int n =0; n<720; n++){
          for (int m=0; m<480; m++){
              if(new Color(image.getRGB(n, m)).getRed()<254){   
//can check any rgb value, I just chose red in this case to check for white pixels    
                  filled[n][m]=true;
              }
          }
        }
      return filled;
}

Upvotes: 0

MadProgrammer
MadProgrammer

Reputation: 347184

You can use BufferedImage#getRGB or byte[] pixels = ((DataBufferByte) bufferedImage.getRaster().getDataBuffer()).getData() to get the pixel data. getRBG is more convenient, but is typically slower than getting the pixel array

getRGB packs the pixel data into an int, getData will return the RGB(A) in each entry of the array (R = n; G = n+1; B=n+2(, A=n+3)), so will need to process this yourself

You can use java.awt.Color, which allows you to access the RGB values of the color, pack it as a int value or convert an int to a Color

Color color = new Color(bufferedImage.getRGB(0, 0), true);
int redColor = Color.RED.getRGB();

The answer to this question provides an example of dealing with the byte[] pixel data

Basically, you will need to loop over the data, comparing the values in the image to the value you are after, either directly (comparing the red, green and blue values) or indirectly, comparing the packed int or Color values.

Personally, I'd grab the pixel data, convert each element to an int and compare it with a previously packed int from a Color object, this creates the less number of short lived objects and should be reasonably efficient

You can take a look at this answer which use getRGB to get the red, green, blue values from a given pixel

Upvotes: 2

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