Develop Reference

Save a BufferedImage to BMP/PNG/JPG and then open it back

I have made a project like Paint from windows and now I want to make the save/open buttons. I have found out how to save the bufferedImage, but the problem is how do I open it back in the correct location and be able to draw on it again?

To read in an image, use ImageIO.
File myPath = new FIle("path to image");
BUfferedImage img = ImageIO.read(myPath);
Also what you could (should) do is load the image into your user space so that you don't edit the original image:
public static BufferedImage userSpace(BufferedImage image)
{
BufferedImage newImage = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
Graphics2D graphics = newImage.createGraphics();
graphics.drawRenderedImage(image, null);
graphics.dispose();
return newImage;
}

Write text on the screen with LWJGL

I want to write text on the screen for my game, for things like fps, random text for items and stuff. How can I write that text?
Is it possible without the Basic Game class? Isn't there a command like this g.drawString("Hello World", 100, 100);?

Update: this answer is now outdated, and does not work at all with the latest versions of LWJGL. Until I update this answer fully, I recommend that you look here: https://jvm-gaming.org/t/lwjgl-stb-bindings/54537
You could use the TrueType fonts feature in the Slick-util library.
Using a common font is easy, just create the font like this:
TrueTypeFont font;
Font awtFont = new Font("Times New Roman", Font.BOLD, 24); //name, style (PLAIN, BOLD, or ITALIC), size
font = new TrueTypeFont(awtFont, false); //base Font, anti-aliasing true/false
If you want to load the font from a .ttf file, it's a little more tricky:
try {
InputStream inputStream = ResourceLoader.getResourceAsStream("myfont.ttf");
Font awtFont = Font.createFont(Font.TRUETYPE_FONT, inputStream);
awtFont = awtFont.deriveFont(24f); // set font size
font = new TrueTypeFont(awtFont, false);
} catch (Exception e) {
e.printStackTrace();
}
After you have successfully created a TrueTypeFont, you can draw it like this:
font.drawString(100, 50, "ABC123", Color.yellow); //x, y, string to draw, color
For more information, you can look at the documentation for TrueTypeFont and java.awt.Font, and the Slick-Util tutorial I got most of this code from.

Try Making a BufferedImage of required size. Then get its Graphics and draw a String. Then Convert it to a ByteBuffer and render it in OpenGL.
String text = "ABCD";
int s = 256; //Take whatever size suits you.
BufferedImage b = new BufferedImage(s, s, BufferedImage.TYPE_4BYTE_ABGR);
Graphics2D g = b.createGraphics();
g.drawString(text, 0, 0);
int co = b.getColorModel().getNumComponents();
byte[] data = new byte[co * s * s];
b.getRaster().getDataElements(0, 0, s, s, data);
ByteBuffer pixels = BufferUtils.createByteBuffer(data.length);
pixels.put(data);
pixels.rewind();
Now pixels contains the required Image data you need to draw.
Use GL11.glTexImage2D() function to draw the byte buffer.

How can I generate text image same as the JLabel label?

I would like to generate text image same as the JLabel label without displaying JLabel.
I tried same Font, same drawing method.
But generated image is not same as JLabel.
My sourcecode is below.
* 'super.paintComponent(g)' has been commented out for clarity that it is the same way. Output image is same.
* Below drawing by 'View.paint' method, but I'm tried 'SwingUtilities2.drawString' too. Two results are the same.
/* Label */
JLabel label = new JLabel(text) {
#Override
public void paintComponent(Graphics g) {
//super.paintComponent(g);
View v = BasicHTML.createHTMLView(this, getText());
v.paint(g, new Rectangle(0, 0, getWidth(), getFontMetrics(
getFont()).getAscent()));
}
};
label.setFont(new Font("Consolas", Font.PLAIN, 13));
/* Image */
FontMetrics fm = label.getFontMetrics(font);
BufferedImage image = new BufferedImage(fm.stringWidth(text),
fm.getHeight(), BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = image.createGraphics();
g2d.setFont(label.getFont());
// Clear background.
g2d.setPaint(label.getBackground());
g2d.fillRect(0, 0, image.getWidth(), image.getHeight());
// Draw string.
g2d.setClip(new Rectangle(0, 0, image.getWidth(), image.getHeight()));
View v = BasicHTML.createHTMLView(label, text);
v.paint(g2d, new Rectangle(0, 0, image.getWidth(),
g2d.getFontMetrics().getAscent()));
// ... output image to file ...
Result image is following.
[JLabel]
[Generated image]
Generated image is slightly thin-faced, as compared to JLabel's capture.
How can I generate text image same as the JLabel label?
Thank you for your consideration.

I'm not sure, but you might need to create a compatible buffered image (compatible to the display)
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice gs = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gs.getDefaultConfiguration();
// Create an image that does not support transparency
BufferedImage bimage = gc.createCompatibleImage(100, 100, Transparency.OPAQUE);
This will at least get you on a close with the graphics been used to render to the screen
You might also like to pay around with the rendering quality as well
Kleopatra did a post on a similar question awhile ago, you might to try and hunt it down

Why do you use BasicHTML.createView if you want to have the same as JLabel?
You could use the JLabel directly (if you only want the text and not the background, set opaque to false and the border to null)
or you can use g2d.drawString()

How to add text to an image in java?

I need to add some texts to an existing table image (png).
Which means that I need to "write" on the image and I need the option to select the text location.
How can I do it?

It's easy, just get the Graphics object from the image and draw your string onto the image. This example (and output image) is doing that:
public static void main(String[] args) throws Exception {
final BufferedImage image = ImageIO.read(new URL(
"http://upload.wikimedia.org/wikipedia/en/2/24/Lenna.png"));
Graphics g = image.getGraphics();
g.setFont(g.getFont().deriveFont(30f));
g.drawString("Hello World!", 100, 100);
g.dispose();
ImageIO.write(image, "png", new File("test.png"));
}
Output (test.png):

Is it possible to create image programmatically on Java, Android?

I need to create .jpeg/.png file on my Android application programmatically. I have simple image (black background), and it need to write some text on it programmatically. How can I do it? Is it possible?

It's definately possible.
To write text on an image you have to load the image in to a Bitmap object. Then draw on that bitmap with the Canvas and Paint functions. When you're done drawing you simply output the Bitmap to a file.
If you're just using a black background, it's probably better for you to simply create a blank bitmap on a canvas, fill it black, draw text and then dump to a Bitmap.
I used this tutorial to learn the basics of the canvas and paint.
This is the code that you'll be looking for to turn the canvas in to an image file:
OutputStream os = null;
try {
File file = new File(dir, "image" + System.currentTimeMillis() + ".png");
os = new FileOutputStream(file);
finalBMP.compress(CompressFormat.PNG, 100, os);
finalBMP.recycle(); // this is very important. make sure you always recycle your bitmap when you're done with it.
screenGrabFilePath = file.getPath();
} catch(IOException e) {
finalBMP.recycle(); // this is very important. make sure you always recycle your bitmap when you're done with it.
Log.e("combineImages", "problem combining images", e);
}

Yes, see here
Bitmap b = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(b);
You can also use awt's Graphics2D with this compatibility project

Using Graphics2d you can create a PNG image as well:
public class Imagetest {
public static void main(String[] args) throws IOException {
File path = new File("image/base/path");
BufferedImage img = new BufferedImage(100, 100,
BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = img.createGraphics();
g2d.setColor(Color.YELLOW);
g2d.drawLine(0, 0, 50, 50);
g2d.setColor(Color.BLACK);
g2d.drawLine(50, 50, 0, 100);
g2d.setColor(Color.RED);
g2d.drawLine(50, 50, 100, 0);
g2d.setColor(Color.GREEN);
g2d.drawLine(50, 50, 100, 100);
ImageIO.write(img, "PNG", new File(path, "1.png"));
}
}