Resizing images with higher DPI makes them dark

[Manish Hatwalne]

I use following code to resize the uploaded images in our application. The resizing works fine, but I am getting darker images when I try to resize images with higher DPI.

BufferedImageOp op = new AffineTransformOp(AffineTransform.getScaleInstance(0.5, 0.5), new   RenderingHints(RenderingHints.KEY_ANTIALIASING, Boolean.TRUE));
BufferedImage bi = op.filter(img, null);

These are my finidings -
(1) When I upload a larger photo which is 72 dpi, the resizer works fine. for example, 1280px wide 72 dpi, will resize to 800 wid 72 dpi and the photo looks fine.

(2) But if the original photo is 300dpi the resizer will convert it to 800 wide 72dpi but the resized photo is VERY dark.

I am wondering what could be causing this and how can I fix this. Any help, pointers wil be highly appreciated!

TIA,
- Manish
[ March 20, 2007: Message edited by: Manish Hatwalne ]

[Manish Hatwalne]

Interestingly, when I resize photo on my local machine (Windows XP) - there is no darkening. But when we test this on our server - it is turing very dark (Linux box) - so I am wondering if there is any property/configuration that I can tweak to get this working?

- Manish

[Manish Hatwalne]

No inputs??? Can anyone tell me what can I do to at least make sure that contrast/brightness is high for resized images??? The image is really very dark!!

[Brandon Broschinsky]

I'm not sure why that wouldn't work on a linux box, I have used the following on linux and windows and it works fine on both of them.

    
BufferedImage scaled = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
scaled.setAccelerationPriority(1);
Graphics2D g2 = scaled.createGraphics();
//Rectangle2D temp;//= new Rectangle2D();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BICUBIC);
int w = image.getWidth();
int h = image.getHeight();
double scale = getScale(w, h,width, height);
double x = (width - scale * w) / 2;
double y = (height - scale * h) / 2;
AffineTransform at = AffineTransform.getTranslateInstance(x,y);
at.scale(scale, scale);
//at.scale(at.getScaleX(),at.getScaleY());
g2.drawImage(image, at, imageO);
g2.dispose();
image=null;
at=null;
 

 
private double getScale(double w, double h, int width, int height) {
double xScale = width / w;
double yScale = height / h;
//double scale = Math.min(xScale, yScale); // scale to fit
double scale = Math.max(xScale, yScale);  // scale to fill
return scale;
}