Change opacity in paint image?

[Before 95]

Right now I'm drawing my paint with the (deprecated) onPaint function, and I have this code right here:

@Override
    public void onPaint(Graphics2D g)
    {
        g.setColor(Color.WHITE);
        g.drawImage(mainPaint, 0, 0, null);
        ...

 and my "mainPaint" is just an image I'm loading through. However, the image itself is opaque.. Is there anyway (through code) I can reduce the opacity of the image?

[Neffarion 465]

AlphaComposite ac = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.50f); // 50% opacity


@Override

public void onPaint(Graphics2D g){

    g.setComposite(ac);

    g.setColor(Color.WHITE);

    g.drawImage(mainPaint, 0, 0, null);

}

 

Edited September 6, 2017 by Neffarion

[Before 95]

AlphaComposite ac = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.50f); // 50% opacity

@Override
public void onPaint(Graphics2D g){
    g.setComposite(ac);
    g.setColor(Color.WHITE);
    g.drawImage(mainPaint, 0, 0, null);
}

Wait does that just like.. make it less opaque? Will try.

 

edit: Works a charm

Edited September 6, 2017 by Before

[ArmyofDragons 28]

The Color constructor relevant to this is (float r, float g, float and (float r, float g, float b, float alpha).

 

You would use the second one I mentioned above in a range from 0.0-1.0 for each value. For example, if you want a black, 30% opacity background for your UI:

// Assume 'g' is passed in as an instance of Graphics2D or Graphics
Color myColor = new Color(0f, 0f, 0f, .3f); // R, G, B, Alpha - The last value, .3f, is opacity.
g.setColor(myColor);
g.fillRect(x, y, width, height);

The solutions that the others have provided above may work but are not a 'standard' way of doing it, considering they require Graphics2D, but it honestly does not matter. Graphics and Graphics2D are the user's preference.

 

You can set the opacity from 0% to 100% on a scale from 0.0f-1.0f with the method I have shown in this post.

Edited September 6, 2017 by ArmyofDragons

[Dinh 496]

The Color constructor relevant to this is (float r, float g, float and (float r, float g, float b, float alpha).

 

You would use the second one I mentioned above in a range from 0.0-1.0 for each value. For example, if you want a black, 30% opacity background for your UI:

// Assume 'g' is passed in as an instance of Graphics2D or Graphics
Color myColor = new Color(0f, 0f, 0f, .3f); // R, G, B, Alpha - The last value, .3f, is opacity.
g.setColor(myColor);
g.fillRect(x, y, width, height);

The solutions that the others have provided above may work but are not a 'standard' way of doing it, considering they require Graphics2D, but it honestly does not matter. Graphics and Graphics2D are the user's preference.

 

You can set the opacity from 0% to 100% on a scale from 0.0f-1.0f with the method I have shown in this post.

The difference is that your approach wont work when you draw an image