Java BufferedImage padding.

Question

Is there any faster way to achieve padding of pixels to a BufferedImage than drawing it centered on larger BufferedImage?

Answer 1

To defer centering until rendering, I like this approach due to finnw, where this is a suitable component:

private BufferedImage image;
....
@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D) g;
    g2d.translate(this.getWidth() / 2, this.getHeight() / 2);
    g2d.translate(-image.getWidth() / 2, -image.getHeight() / 2);
    g2d.drawImage(image, 0, 0, null);
}

Answer 2

Create an ImageIcon using the BufferedImage and add the Icon to a JLabel. Then you can just add a Border to the label to get your desired padding.

Answer 3

BufferedImage has a constructor where you get to specify a WriteableRaster.

Picking at the a default buffered image, storing each pixel in an int, it uses an IntegerInterleavedRaster.

The ColorModel you can use ColorModel.getRGBDefault().

int imageWidth = 638, imageHeight = 480;
int dataImageWidth = 640;

SampleModel sm = new SinglePixelPackedSampleModel(TYPE_INT, imageWidth, imageHeight, dataImageWidth, new int[] { 0xff0000, 0xff00, 0xff });
DataBuffer db = new DataBufferInt(dataImageWidth * imageHeight);
WritableRaster r = Raster.createWritableRaster(sm, db, new Point());
BufferedImage image = new BufferedImage(ColorModel.getRGBDefault(), r, false, null);

Notice the scanlineStride in SinglePixelPackedSampleModel (second last parameter).

Another much simpler approach is to use BufferedImage's getSubimage method.

BufferedImage fullImage = new BufferedImage(dataImageWidth, imageHeight);
BufferedImage subImage = fullImage.getSubimage(0, 0, imageWidth, imageHeight);