Getting pixel data from an image using java

Question

I\'m trying to get the pixel rgb values from a 64 x 48 bit image. I get some values but nowhere near the 3072 (= 64 x 48) values that I\'m expectin

Answer 1

int argb = img.getRGB(x, y); Your code

int argb = img.getRGB(y, x); my changes now it works

Answer 2

This:

for(int i = 0; i < img.getHeight(); i++){
    for(int j = 0; j < img.getWidth(); j++){
        rgb = getPixelData(img, i, j);

Does not match up with this:

private static int[] getPixelData(BufferedImage img, int x, int y) {

You have i counting the rows and j the columns, i.e. i contains y values and j contains x values. That's backwards.

Answer 3

Why didn't use just use:

public int[] getRGB(int startX,
                    int startY,
                    int w,
                    int h,
                    int[] rgbArray,
                    int offset,
                    int scansize)

It's built-in, man.

Answer 4

I was looking for this same ability. Didn't want to enumerate the entire image, so I did some searching and used PixelGrabber.

Image img = Toolkit.getDefaultToolkit().createImage(filename);
PixelGrabber pg = new PixelGrabber(img, 0, 0, -1, -1, false);

pg.grabPixels(); // Throws InterruptedException

width = pg.getWidth();
height = pg.getHeight();

int[] pixels = (int[])pg.getPixels();

You could use the int[] directly here, pixels are in a format dictated by the ColorModel from pg.getColorModel(), or you can change that false to true and force it to be RGB8-in-ints.

I've since discovered that the Raster and Image classes can do this too, and there have been some useful classes added in javax.imageio.*.

BufferedImage img = ImageIO.read(new File(filename)); // Throws IOException
int[] pixels = img.getRGB(0,0, img.getWidth(), img.getHeight, null, 0, img.getWidth());

// also available through the BufferedImage's Raster, in multiple formats.
Raster r = img.getData();
int[] pixels = r.getPixels(0,0,r.getWidth(), r.getHeight(), (int[])null);

There are several getPixels(...) methods in Raster as well.

Answer 5

You have to change:

for(int i = 0; i < img.getHeight(); i++){
    for(int j = 0; j < img.getWidth(); j++){
        rgb = getPixelData(img, i, j);

Into

for(int i = 0; i < img.getWidth(); i++){
    for(int j = 0; j < img.getHeight(); j++){
        rgb = getPixelData(img, i, j);

Because the second parameter from getPixelData is the x-value and the thirth is the y-value. You switched the parameters.

Answer 6

This works too:

BufferedImage img = ImageIO.read(file);

int[] pixels = ((DataBufferInt)img.getRaster().getDataBuffer()).getData();