Develop Reference

How to draw transparent image in java with BufferedImage?

I'm willing to show an transparent image on a canvas in java with the help of graphics2D and BufferedImage.
Here is the code which loads image.
private static BufferedImage sprites,board;
public static void load(){
try {
board = new BufferedImage(100,100,BufferedImage.TYPE_INT_ARGB);
board = ImageIO.read(new File("res/chesssprite.png"));
} catch (IOException ex) {
Logger.getLogger(SpriteManager.class.getName()).log(Level.SEVERE, null, ex);
}
}
and here is the code which renders the image
public void render(){
BufferStrategy bs = this.getBufferStrategy();
if(bs == null){
this.createBufferStrategy(3);
return;
}
Graphics g = bs.getDrawGraphics();
Graphics2D g2d = (Graphics2D) g;
{
g2d.setColor(new Color(150,150,150));
g2d.fillRect(0,0,getWidth(), getHeight());
g2d.setComposite(AlphaComposite.Src);
g2d.drawImage(board,0,0,null);
}
g = g2d;
g.dispose();
bs.show();
}
I have search on net a lot but didn't come with an solution. If anyone knowns how to fix this.
Here is the image..
And here is how output looks like

Okay whoever facing these kind of problem:
Make sure the image is transparent. Test it in image viewer.
Remove the line g2d.setComposite(AlphaComposite.Src); This line adds alpha composites which make every transparent pixel black.

Java: How to fill shape from an ArrayList with color?

I have an ArrayList of Shapes (Rectangles and Ovals) and I want to paint these shapes. How do I fill them with color in the for loop?
My ArrayList is composed of both Rectangles and Ovals. If I do fillRect(color), it paints all shapes as Rectangles, and if I do fillOval(color), it paints all shapes as Ovals. How can I fill the Ovals and Rectangles appropriately? The code below only does the outlines.
private ArrayList<Shape> shapes = new ArrayList<Shape>();
private Shape currentShape; // the shape being drawn (either Rectangle or Oval)
public void paintComponent(Graphics g) {
super.paintComponent(g);
for(Shape s : shapes) {
Graphics2D g2d = (Graphics2D) g.create();
s.paint(g2d);
}
}

Graphics2D.fill(Shape) will do.
private List<Shape> shapes = new ArrayList<>();
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.RED);
for (Shape shape : shapes) {
g2d.fill(shape);
}
}
No g.create. The fact that every paintComponent parameter is actually a Graphics2D is historically founded: they replaced Graphics by a more exhaustive Graphics2D, but for backward compatibility kept Graphics.

How do I fill them with color in the for loop?
You need to store the Color information with the Shape. So you need to create a custom object with two properties: "shape" and "color". Then you can set the Graphics Color before you paint the Shape.
See Custom Painting Approaches for a working example of this approach.

The dicom bufferedImage from pixelmed is having low contrast

I would like to display a DICOM image in my java program. I am using pixelmed. However, I found that i cant correctly display the correct contrast. The contrast is too low.
Here is my code:
(SourceImage is a class provided by PixelMed, chosenImageFile.getPath() is just the path of the DICOM File.)
SourceImage dimg = new SourceImage(chosenImageFile.getPath());
BufferedImage image = dimg.getBufferedImage();
BufferedImage source = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = source.createGraphics();
g2d.drawImage(image, 0, 0, null);
dicomImgDisplayer1.setImage(source);
dicomImgDisplayer1 is an class extend JPanel. setImage() of this JPanel class will call the setImage() of an JFrame class.
The JFrame class's setImage() code:
public void setImage(BufferedImage image) {
this.image = image;
setPreferredSize(new Dimension(image.getWidth(), image.getHeight()));
repaint();
revalidate();
}
public void paint(Graphics graphics) {
Graphics2D g2d = (Graphics2D) graphics;
g2d.drawImage(image, null, 0, 0);
}
Is that something wrong with the color model? Please help. Thanks.

Does your image have a prescribed window width / window center? Be sure you set that (or allow the user to adjust it). See SingleImagePanel - there are some static methods to apply windowing to your buffered image.

BufferStrategy not scaling Graphics2D

I am currently trying to program a simple platform game. I would like to scale the graphics up by a factor of 2/4/whatever so that I can get an old-school look and feel from the game. However, when I call scale on my Graphics2D instance, nothing happens.
#Override
public void paint(Graphics g) {
BufferStrategy bf = this.getBufferStrategy();
Graphics2D bfg = (Graphics2D) bf.getDrawGraphics();
mLevel.draw(bfg, this);
for (GameEntity entity : mGameEntities) {
entity.draw(bfg, this);
}
bfg.scale(2.0, 2.0);
bf.show();
}
The draw calls basically just end up calling g.drawImage(..). Everything else is drawn correctly, so I do not understand why it isn't scaling everything up by a factor of 2.

#MadProgrammer was correct - one must scale the Graphics2D instance before making any draw calls.
#Override
public void paint(Graphics g) {
BufferStrategy bf = this.getBufferStrategy();
Graphics2D bfg = (Graphics2D) bf.getDrawGraphics();
bfg.scale(2.0, 2.0);
mLevel.draw(bfg, this);
for (GameEntity entity : mGameEntities) {
entity.step();
entity.draw(bfg, this);
}
bf.show();
}

java.awt.Graphics change color after drawing

I have asked a similar question a while ago here, but didn't get an answer. The original question was about changing the color of a shape after clicking on it. But I am puzzled on how to access the shape at all after it is drawn.
This is my paintComponent method
#Override
protected void paintComponent(Graphics graph) {
super.paintComponent(graph);
Graphics2D g = (Graphics2D) graph;
// smooth graphics
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// moving to the middle of the panel
g.translate(this.getWidth()/2, this.getHeight()/2);
// painting colored arcs
for(int i = 0; i < 4; i++) {
g.setColor(dimColors[i]);
g.fill(arcs[i]);
}
// painting borders
g.setColor(Color.BLACK);
g.setStroke(new BasicStroke(5F));
g.drawLine(-98, 0, 98, 0);
g.drawLine(0, -98, 0, 98);
g.draw(circle);
// painting central white circle
g.setColor(Color.WHITE);
g.fill(smallCircle);
g.setColor(Color.BLACK);
g.draw(smallCircle);
}
the arcs[] array contains a bunch of Arc2D's that are drawn on the panel. My question is now, if I want to change the color of, for example arcs[0], how do I do that?
Thanks!
EDIT: I now have this MouseAdapter event
private class MyMouseAdapter extends MouseAdapter {
public void mousePressed(MouseEvent e) {
Point p = e.getPoint();
Component c = getComponentAt(p);
Graphics g = c.getGraphics();
dimColors[1] = Color.RED;
paintComponent(g);
}
}
And it works, it changes the color of arc[1] because arcs[1] has dimColors[1] set as color when drawing it.
However, I still can't figure out how to check wether the right arc was clicked. Right now you just click anywhere on the graphics panel and it changes the color of that specific arc

This doesn't answer your earlier question, however it does answer your question of click detection. To do this it is best to use Graphics2D because it is a lot easier to write than most other options. Here is an example:
public class GraphicsPanel extends JPanel implements MouseListener
{
private Rectangle2D rect;
First we create our Graphics2D rectangle rect.
public void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D)(g);
g2d.setColor(Color.GREEN);
rect = new Rectangle2D.Double(70, 70, 100, 100);
g2d.fill(rect);
this.addMouseListener(this);
}
And then we override the paintComponent method and create our new Rectangle2D.Double object.
We then fill the rectangle with g2d.fill() and then add a mouse listener to the JPanel.
public void mousePressed(MouseEvent e)
{
if(rect.contains(e.getX(), e.getY()))
System.out.println("Rectangle clicked");
}
}
Finally, we need to see if that rectangle contains the point where the user clicked. To do this, simply see if the rectangle we created contains the user's click location by using the Rectangle2D.double's contains(int x, int y) method. That's it!

if I want to change the color of, for example arcs[0], how do I do that?
A line (or whatever) only exists as a bunch of pixels that were painted in the original color. To change its color you must change the current color and draw it again.