Center image on canvas

Question

Hi,
the following code scales an image (srcImage) to a maximum size (maxSize).
My aim is to center this image on a square canvas of maxSize.
The existing code so far:
  public BufferedImage fitImage(BufferedImage srcImage, int maxSize)
    // determine scaling factor for optimal fitting
    double scaleX = (double) maxSize/srcImage.getWidth();
    double scaleY = (double) maxSize/srcImage.getHeight();
    double scale = Math.min(scaleX, scaleY);
    // blur image
    if (scale <= 0.5)
      int radius = (int) Math.floor(1 / scale);
      srcImage = blur(srcImage, radius);
    // create new image buffer
    int newWidth = (int) (srcImage.getWidth() * scale);
    int newHeight = (int) (srcImage.getHeight() * scale);
    WritableRaster dstRaster = srcImage.getRaster().createCompatibleWritableRaster(newWidth, newHeight);
    BufferedImage dstImage = new BufferedImage(srcImage.getColorModel(), dstRaster, false, new Hashtable());
    // scale image
    AffineTransformOp op = new AffineTransformOp(AffineTransform.getScaleInstance(scale, scale), AffineTransformOp.TYPE_BILINEAR);
    op.filter(srcImage, dstImage);
    return dstImage;
  }Any hints how to do this?
Cheers
Jonny

Answer 1

Hi Darryl,
Thanks for your great help.
I think we partitially talked at cross-purposes, because of my bad description of the problem. My bad!
My aim was to first proportionally scale down an image to either x or y in maxSize.
Then draw it on a (white) canvas with size x: maxSize, y: maxsize.
For now I solved it this way:
public BufferedImage fitImage(BufferedImage srcImage, int maxSize)
    // determine scaling factor for optimal fitting
    double scaleX = (double) maxSize/srcImage.getWidth();
    double scaleY = (double) maxSize/srcImage.getHeight();
    double scale = Math.min(scaleX, scaleY);
    // blur image
    if (scale <= 0.5)
      int radius = (int) Math.floor(1 / scale);
      srcImage = blur(srcImage, radius);
    // create new image buffer
    int newWidth = (int) (srcImage.getWidth() * scale);
    int newHeight = (int) (srcImage.getHeight() * scale);
    WritableRaster dstRaster = srcImage.getRaster().createCompatibleWritableRaster(newWidth, newHeight);
    BufferedImage dstImage = new BufferedImage(srcImage.getColorModel(), dstRaster, false, new Hashtable());
    // scale image
    AffineTransformOp op = new AffineTransformOp(AffineTransform.getScaleInstance(scale, scale), AffineTransformOp.TYPE_BILINEAR);
    op.filter(srcImage, dstImage);
    BufferedImage canvasImage = new BufferedImage(maxSize, maxSize, srcImage.getType());
    Graphics2D g2 = canvasImage.createGraphics();
    g2.setColor(Color.WHITE);
    g2.fillRect( 0, 0, maxSize, maxSize );
    g2.drawImage( dstImage,
        ( maxSize - dstImage.getWidth( null ) ) / 2,
        ( maxSize - dstImage.getHeight( null ) ) / 2,
        null );
    return canvasImage;
  }If someone has a better way (I bet there is one) feel free to tell me.
Cheers
Jonny