How to get the array of pixel values for an image in java using getRGB

问题

I'm new to image processing in java. Actually what I'm trying to do is to save all the pixel values of an image into an array rgbArray[], and the problem is that I'm getting the same values in all the indexes of an array i.e. all the indexes of the array have the same value. A part of code is given below:

int[] rgbArray=new int[w*h];     // Array to store the Pixel values
BufferedImage buffer = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); 
buffer.getRGB(0, 0, w, h, rgbArray, 0, w );
for(int i=0;i<w*h;i++)
 {
  System.out.println("rgbArray["+i+"] = "+ rgbArray[i]);
 }

The output which i'm getting is -16777216 for all indexes in rgbArray. How is it possible to have the same value for each and every pixel of the image? And how do I get the correct pixel value??

回答1:

Since you do not provide any values for the BufferedImage, every pixel defaults to alpha = 255, red = 0, green = 0, and blue = 0; Put all of those into 1 int and you get -16777216. I got this from:

int val = buffer.getRGB(5, 23);
int a = (0xff000000 & val) >>> 24;
int r = (0x00ff0000 & val) >> 16;
int g = (0x0000ff00 & val) >> 8;
int b = (0x000000ff & val);
System.out.println("a " + a + " r " + r + " g " + g + " b " + b);

Which produces a 255 r 0 g 0 b 0.

来源：https://stackoverflow.com/questions/8856569/how-to-get-the-array-of-pixel-values-for-an-image-in-java-using-getrgb