获取图像的所有RGB颜色

Question

So far I have this:

BufferedImage image = ImageIO.read(
     new URL("http://upload.wikimedia.org/wikipedia/en/2/24/Lenna.png"));

int w = image.getWidth();
int h = image.getHeight();

int[] dataBuffInt = image.getRGB(0, 0, w, h, null, 0, w); 

Color c = new Color(dataBuffInt[100]);

System.out.println(c.getRed());   // = (dataBuffInt[100] >> 16) & 0xFF
System.out.println(c.getGreen()); // = (dataBuffInt[100] >> 8)  & 0xFF
System.out.println(c.getBlue());  // = (dataBuffInt[100] >> 0)  & 0xFF
System.out.println(c.getAlpha()); // = (dataBuffInt[100] >> 24) & 0xFF

Earlier, I tried putting the getRed , getGreen , and getBlue in a for loop but it only shows the same RGB value. How do I get all the RGB values in an image? Given that I wanna store them in different arrays.

Answer 1

I'm not entirely clear on the question, but assuming you mean unique RGB values, just loop, and just use say java.util.Set implementation that maintains uniqueness?

Set<Color> colors = new HashSet<Color>();
for (int datum : dataBuffInt) {
    colors.add(new Color(datum));
}
System.out.println(String.format("%d different colors", colors.size()));

Or if you mean separate components?

for (int datum : dataBuffInt) {
    Color color = new Color(datum);
    reds.add(color.getRed());
    greens.add(color.getGreen());
    blues.add(color.getBlue());

}
System.out.println(String.format("reds: %d greens: %d blues: %d", reds.size(), greens.size(), blues.size()));

Answer 2

Are you certain when you had the for loop you were using the index variable into the array and not a static value, like 100 ? When I run your code with a for loop I see different values:

for (int i = 0; i < dataBuffInt.length; i++) {
    Color c = new Color(dataBuffInt[i]);

    System.out.println("COLOR");
    System.out.println(c.getRed());   // = (dataBuffInt[100] >> 16) & 0xFF
    System.out.println(c.getGreen()); // = (dataBuffInt[100] >> 8)  & 0xFF
    System.out.println(c.getBlue());  // = (dataBuffInt[100] >> 0)  & 0xFF
    System.out.println(c.getAlpha()); // = (dataBuffInt[100] >> 24) & 0xFF
    System.out.println();
}

If you want unique colors you could build a set one pixel at a time:

final BufferedImage image = ImageIO.read(new URL("http://upload.wikimedia.org/wikipedia/en/2/24/Lenna.png"));
final Set<Color> uniqueColors = new HashSet<Color>(image.getWidth() * image.getHeight());
for (int y = 0; y < image.getHeight(); y++) {
    for (int x = 0; x < image.getWidth(); x++) {
        final int rgb = image.getRGB(x, y);
        uniqueColors.add(new Color(rgb));
    }
}

for (final Color color : uniqueColors) {
    System.out.println(format("red: {0}, green: {1}, blue: {2}, alpha: {3}",
            color.getRed(),
            color.getGreen(),
            color.getBlue(),
            color.getAlpha()));
}

Or use your existing code and dump the array into a set.