How can I display an image from an array of pixels' values in java?

Question

I intended to display a 28x28 pixels image inside the window. The pixels have "0" value, so I expected it to display a window with a black square of 28x28. But no image is displayed instead. Maybe array's data (I don't know for sure if pixel values must be an int in range from 0 to 255) must be other in order to display the image. Thanks!

public class ASD {

public static Image getImageFromArray(int[] pixels, int width, int height) {
    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    WritableRaster raster = (WritableRaster) image.getData();
    System.out.println(pixels.length + " " + width + " " + height);
    raster.setPixels(0,0,width,height,pixels);
    return image;
}

public static void main(String[] args) throws IOException {
    JFrame jf = new JFrame();
    JLabel jl = new JLabel();

    int[] arrayimage = new int[784];
    for (int i = 0; i < 28; i++)
    {   for (int j = 0; j < 28; j++)
            arrayimage[i*28+j] = 0;
    }
    ImageIcon ii = new ImageIcon(getImageFromArray(arrayimage,28,28));
    jl.setIcon(ii);
    jf.add(jl);
    jf.pack();
    jf.setVisible(true);
}

Atreys · Accepted Answer · 2011-05-27 20:51:42Z

3

image.getData() returns a copy of the raster. Perhaps if you call image.setData(raster) after you modify the raster you will see results.

Also, setPixels should be given an array large enough to fill all the bands (A, R, G, B) of the raster. I had gotten an array index out of bounds exception until I increased the size of pixels to be 28*28*4.

For TYPE_INT_RGB, the following should produce a white image:

public class ASD
{
  public static Image getImageFromArray(int[] pixels, int width, int height)
  {
    BufferedImage image =
        new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    WritableRaster raster = (WritableRaster) image.getData();
    raster.setPixels(0, 0, width, height, pixels);
    image.setData(raster);
    return image;
  }

  public static void main(String[] args) throws IOException
  {
    JFrame jf = new JFrame();
    JLabel jl = new JLabel();

    //3 bands in TYPE_INT_RGB
    int NUM_BANDS = 3;
    int[] arrayimage = new int[28 * 28 * NUM_BANDS];

    for (int i = 0; i < 28; i++)
    {
      for (int j = 0; j < 28; j++) {
        for (int band = 0; band < NUM_BANDS; band++)
          arrayimage[((i * 28) + j)*NUM_BANDS + band] = 255;
      }
    }
    ImageIcon ii = new ImageIcon(getImageFromArray(arrayimage, 28, 28));
    jl.setIcon(ii);
    jf.add(jl);
    jf.pack();
    jf.setVisible(true);
  }
}

edited May 27, 2011 at 20:51

answered May 27, 2011 at 20:25

Atreys

3,7611 gold badge19 silver badges29 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Alexander Over a year ago

I've changed: 1) array size to 28*28*3(all 0 values), 2)TYPE_INT_ARGB to TYPE_INT_RGB, 3) and called image.setData(raster) after setPixels. But still no image is displayed.

Atreys Over a year ago

@Alexander, above is your code changed to produce a white image. It works for me anyway... Are you getting a JFrame, or is your program terminating without any effect?

leonbloy · Accepted Answer · 2011-05-27 20:27:45Z

1

I dont know it this is the problem, but you are using TYPE_INT_ARGB. This includes an Alpha channel (opacy) in the packed integer, a value of 0 means fully transparent.

Another one (read the docs!):

BufferedImage.getData() :  The Raster returned is a copy of the image data is not updated if the image is changed.

You must call setData() to place the new pixels inside the image, I think.

edited May 27, 2011 at 20:27

answered May 27, 2011 at 19:56

leonbloy

76.4k22 gold badges149 silver badges197 bronze badges

3 Comments

Alexander Over a year ago

Ok, I changed it to TYPE_INT_RGB; but the problem persists. And also the image is not displayed regardless of array values, be it 0 or any other value. Thanks.

Alexander Over a year ago

Must the array be of the size = widthheight*3, for every channel; where 0..widthheight contains the values of red, widthheight+1..2*widthheight the values of green and 2*widthheight+1..widthheight*3 the values of blue? Thanks.

leonbloy Over a year ago

TYPE_INT_RGB packs the three samples (one for each pixel) that compose a pixel in a single integer.

Collectives™ on Stack Overflow

How can I display an image from an array of pixels' values in java?

2 Answers 2

2 Comments

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related