FULL PRODUCT VERSION :
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Linux 3.13.0-63-generic #103-Ubuntu SMP Fri Aug 14 21:42:59 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux


A DESCRIPTION OF THE PROBLEM :
Alpha channel of background is missing when drawing scaled image through Graphics2D#drawImage(Image, int, int, int, int, Color, ImageObserver) and Graphics2D#drawImage(Image, int, int, int, int, int, int, int, int, Color, ImageObserver).
When image is unscaled, alpha channel is used as normal.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the attached simple test case. The left image is unscaled and background is correct. The right image is scaled and alpha channel is lost.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Scaled image with semitransparent background just like the left one's.
ACTUAL -
Scaled image with opaque background.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.*;
import java.awt.image.*;

import javax.swing.*;

public class Test {
public static void main(String[] args) {
JFrame frame = new JFrame("test");
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
JPanel content = new JPanel() {
@Override
public void paint(Graphics g) {
Image img = new BufferedImage(50, 50, BufferedImage.TYPE_INT_ARGB);
Graphics2D imgGraphics = (Graphics2D) img.getGraphics();
imgGraphics.setColor(Color.blue);
imgGraphics.fillRect(10, 10, 30, 30);
imgGraphics.dispose();
g.setColor(Color.pink);
g.fillRect(0, 0, 100, 50);
g.drawImage(img, 0, 0, new Color(0, 255, 255, 128), null);
g.drawImage(img, 55, 5, 40, 40, new Color(0, 255, 255, 128), null);
}
};
frame.getContentPane().add(content);
frame.setSize(100, 50);
frame.setVisible(true);
}
}
---------- END SOURCE ----------