ADDITIONAL SYSTEM INFORMATION :
Windows 10

A DESCRIPTION OF THE PROBLEM :
Using the Graphics2D class function drawLine to draw a line angled at 45° in the upward direction (x1 < x2 and y1 > y2), while using a color with an alpha value different than full opacity (alpha < 255) yields a line with double the thickness then when either using a fully opaque color or when drawing a line in the downward direction (x1 < x2 and y1 < y2) angled at 45° while using a color with arbitrary opacity (alpha <= 255).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the attached code and look at the output file named "transparent.png".

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The pixels to which the line is drawn in the "transparent.png" output file should be the same ones that are drawn in the "opaque.ong" output file.
ACTUAL -
The line drawn in the "transparent.png" output file has double the width than the one drawn in the "opaque.png" output file.

---------- BEGIN SOURCE ----------
package main.app;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class Program {
    public static void main(String[] args) throws IOException {
        BufferedImage transparentImage = new BufferedImage(50, 50, BufferedImage.TYPE_INT_ARGB);
        Graphics2D transparentGraphics = transparentImage.createGraphics();

        transparentGraphics.setBackground(Color.WHITE);
        transparentGraphics.fillRect(0, 0, transparentImage.getWidth(), transparentImage.getHeight());

        transparentGraphics.setPaint(new Color(0, 0, 0, 128));
        transparentGraphics.drawLine(0, 49, 49, 0);

        transparentGraphics.dispose();
        ImageIO.write(transparentImage, "png", new File("transparent.png"));

        BufferedImage opaqueImage = new BufferedImage(50, 50, BufferedImage.TYPE_INT_ARGB);
        Graphics2D opaqueGraphics = opaqueImage.createGraphics();

        opaqueGraphics.setBackground(Color.WHITE);
        opaqueGraphics.fillRect(0, 0, opaqueImage.getWidth(), opaqueImage.getHeight());

        opaqueGraphics.setPaint(new Color(0, 0, 0, 255));
        opaqueGraphics.drawLine(0, 49, 49, 0);

        opaqueGraphics.dispose();
        ImageIO.write(opaqueImage, "png", new File("opaque.png"));
    }
}
---------- END SOURCE ----------

FREQUENCY : always