How to scale JPEG images with a non-standard sampling factor in Java?
- by HRJ
I am using Java AWT for scaling a JPEG image, to create thumbnails. The code works fine when the image has a normal sampling factor ( 2x2,1x1,1x1 )
However, an image which has this sampling factor ( 1x1, 1x1, 1x1 ) creates problem when scaled. The colors get corrupted though the features are recognizable.
The original and the thumbnail:
The code I am using is roughly equivalent to:
static BufferedImage awtScaleImage(BufferedImage image,
int maxSize, int hint) {
// We use AWT Image scaling because it has far superior quality
// compared to JAI scaling. It also performs better (speed)!
System.out.println("AWT Scaling image to: " + maxSize);
int w = image.getWidth();
int h = image.getHeight();
float scaleFactor = 1.0f;
if (w > h)
scaleFactor = ((float) maxSize / (float) w);
else
scaleFactor = ((float) maxSize / (float) h);
w = (int)(w * scaleFactor);
h = (int)(h * scaleFactor);
// since this code can run both headless and in a graphics context
// we will just create a standard rgb image here and take the
// performance hit in a non-compatible image format if any
Image i = image.getScaledInstance(w, h, hint);
image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
Graphics2D g = image.createGraphics();
g.drawImage(i, null, null);
g.dispose();
i.flush();
return image;
}
(Code courtesy of this page )
Is there a better way to do this?
Here's a test image with sampling factor of [ 1x1, 1x1, 1x1 ].
