Crop an Image object to create smaller images from it...

is there a way to load this ONE big PNG into an Image obj (say imgObj) and then draw only a part of this imgObj, say x,y - 10, 10 width, height 30,30?

To take any part of an image and draw it anywhere on a component? Yes.

Here's an attempt at showing two ways of doing this.

import java.awt.*;

import java.awt.font.*;

import java.awt.geom.AffineTransform;

import java.awt.image.BufferedImage;

import javax.swing.*;

public class ClippedDrawing {

private JPanel getContent() {

BufferedImage image = makeImage();

ClippedDrawingPanel cdp = new ClippedDrawingPanel(image);

// Display components at their preferredSize.

JPanel panel = new JPanel(new GridBagLayout());

GridBagConstraints gbc = new GridBagConstraints();

gbc.insets = new Insets(5,5,5,5);

panel.add(new JLabel(new ImageIcon(image)), gbc);

panel.add(cdp, gbc);

return panel;

}

private BufferedImage makeImage() {

int w = 240;

int h = 240;

int type = BufferedImage.TYPE_INT_RGB;

BufferedImage image = new BufferedImage(w, h, type);

Graphics2D g2 = image.createGraphics();

g2.setPaint(new GradientPaint(0, 0, new Color(200,220,200),

w, h, new Color(240,200,220)));

g2.fillRect(0,0,w,h);

int size = 8;

int inc = w/size;

System.out.println("inc = " + inc);

g2.setPaint(Color.blue);

for(int j = 0, y = inc; j < size; j++, y+=inc)

g2.drawLine(0,y,w,y);

for(int j = 0, x = inc; j < size; j++, x+=inc)

g2.drawLine(x,0,x,h);

Font font = g2.getFont().deriveFont(14f);

g2.setFont(font);

FontRenderContext frc = g2.getFontRenderContext();

g2.setPaint(Color.red);

for(int j = 0; j < size; j++) {

for(int k = 0; k < size; k++) {

String s = String.valueOf(j*size + k+1);

float width = (float)font.getStringBounds(s, frc).getWidth();

LineMetrics lm = font.getLineMetrics(s, frc);

float height = lm.getAscent() + lm.getDescent();

float x = k*inc + (inc - width)/2;

float y = j*inc + (inc + height)/2 - lm.getDescent();

g2.drawString(s, x, y);

}

}

g2.dispose();

return image;

}

public static void main(String[] args) {

ClippedDrawing test = new ClippedDrawing();

JFrame f = new JFrame();

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

f.getContentPane().add(test.getContent());

f.pack();

f.setLocationRelativeTo(null);

f.setVisible(true);

}

}

class ClippedDrawingPanel extends JPanel {

BufferedImage image;

Rectangle clip;

public ClippedDrawingPanel(BufferedImage image) {

this.image = image;

clip = new Rectangle(50, 50);

}

protected void paintComponent(Graphics g) {

super.paintComponent(g);

Graphics2D g2 = (Graphics2D)g;

int w = getWidth();

int h = getHeight();

// Save the original clip for later.

Shape origClip = g2.getClip();

// Mark the boundry of this component.

g2.setPaint(Color.magenta);

g2.draw(new Rectangle(0,0,w-1,h-1));

//// Technique 1: manipulate the clip and the image ////

// Draw the rectangular section [x, y, 50, 50] of image.

// Choose an arbitrary location in the image:

int x = 40;

int y = 60;

// Locate this section at clipX, clipY on this component.

// We can render this small image section anywhere we want

// within this component. Choose an arbitrary location:

int clipX = (w - clip.width)/2;

int clipY = 25;

// Move clip to this location. The image section specified above

// will be rendered at this location in this component.

clip.setLocation(clipX, clipY);

// Set the clip to restrict the next drawing operation.

g2.setClip(clip);

// Move the image so that our selected section appears

// in the clip set in this components coordinate system.

// Comment out the setClip call above and un-comment the

// draw(clip) call below to see this.

double tx = clipX - x;

double ty = clipY - y;

AffineTransform at = AffineTransform.getTranslateInstance(tx, ty);

g2.drawRenderedImage(image, at);

//g2.draw(clip);

// Reset the clip to its original value.

g2.setClip(origClip);

//// Technique 2: use a subimage ////

// Draw the rectangular section [x, y, 50, 50] of image.

// Choose an arbitrary location in the image:

x = 150;

y = 120;

// Reuse clip for obtaining the subImage

// which will be drawn on this component.

clip.setLocation(x, y);

BufferedImage subImage = getSubimage(clip);

// Choose an arbitrary location to draw this subImage

// into this component.

int locX = (w - clip.width)/2;

int locY = h - clip.height - 40;

// Draw the subImage at this location.

g2.drawImage(subImage, locX, locY, this);

}

private BufferedImage getSubimage(Rectangle r) {

// Boundry checking is advisable here.

BufferedImage subImage = null;

try {

subImage = image.getSubimage(r.x, r.y, r.width, r.height);

} catch(ArrayIndexOutOfBoundsException e) {

System.out.println("AIOOBE: " + e.getMessage());

}

return subImage;

}

public Dimension getPreferredSize() {

return new Dimension(160, 200);

}

}

crwooda at 2007-7-10 2:42:54 >