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Thread: What does this part of the code mean?

  1. #1
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    Default What does this part of the code mean?

    I am studying a code that allows you to browse for one image, and then the program opens up two windows. The window on the left displays the image and the one on the right displays the same exact image but with a weird effect. I am trying to fully understand the code but I'm having trouble understanding this part of the code from one of the classes:

    //
    	// Transition by rows left to right top to bottom
    	public void transitionLRTB(Graphics g, BufferedImage leftImage) 
    	{
    		int width = leftImage.getWidth();
    		int height = leftImage.getHeight();
    		for (int j=0; j<height; j++)
    		{
    			for (int i=0; i<width; i++)
    			{
    				int pixelColor= leftImage.getRGB(i,j);
    				img.setRGB(i, j, pixelColor);
    			}
    			repaint();
    			try { Thread.sleep(10); } catch (InterruptedException e) { };
    		}
    	}


    I know it's a mutator object but I stop understanding what it does once it starts dealing with iterations and ++'s.

    Here is the full code:

    import java.awt.Graphics;
    import java.awt.Image;
    import java.awt.image.BufferedImage;
     
    import javax.swing.JPanel;
     
     
    public class LeftPanel extends JPanel 
    {
     
    	private BufferedImage img;
     
    	public LeftPanel(BufferedImage img)
    	{
    		this.img = img;
    	}
     
    	public void paintComponent (Graphics g){
    		super.paintComponent(g);
    		g.drawImage(this.img, 0, 0 , null);		
    	}
    }


    public void transitionLRTB(Graphics g, BufferedImage leftImage) 
    	{
    		int width = leftImage.getWidth();
    		int height = leftImage.getHeight();
    		for (int j=0; j<height; j++)
    		{
    			for (int i=0; i<width; i++)
    			{
    				int pixelColor= leftImage.getRGB(i,j);
    				img.setRGB(i, j, pixelColor);
    			}
    			repaint();
    			try { Thread.sleep(10); } catch (InterruptedException e) { };
    		}
    	}
     
    	//
    	// Transition by diagonals bottom to top left to right
    	public void transitionDiagonal45LR(Graphics g, BufferedImage leftImage)
    	{
    		int width = leftImage.getWidth();
    		int height = leftImage.getHeight();
    		for (int row=0; row<height; row++)
    		{
    			int diagonalRow = row;
    			for (int col=0; col<=row; col++) 
    			{
    				int pixelColor= leftImage.getRGB(col,diagonalRow);
    				img.setRGB(col, diagonalRow, pixelColor);
    				diagonalRow--;
    			}
    			repaint();
    			try { Thread.sleep(10); } catch (InterruptedException e) 
    			{ };
    		}
     
    		if (width > height) 
    		{
    			// Image with larger width than height		
    			for (int i=0; i<(width-height); i++) 
    			{
    				int row = height-1;
    				int col = i+1;
    				for (int j=0; j<height; j++) 
    				{
    					int pixelColor= leftImage.getRGB(col,row);
    					img.setRGB(col, row, pixelColor);
    					col++; row--;
    				}
    				repaint();
    				try { Thread.sleep(10); } catch (InterruptedException e) { };
    			}
     
    			for (int i=0; i<=(width); i++) 
    			{
    				int diagonalRow = height-1;
    				for (int col=(width-height+i); col<width; col++) 
    				{
    					int pixelColor= leftImage.getRGB(col,diagonalRow);
    					img.setRGB(col, diagonalRow, pixelColor);
    					diagonalRow--;
    				}
    				repaint();
    				try { Thread.sleep(10); } catch (InterruptedException e) { };
    			}
    		}
    		else {
    			// Lab Q2: Add code to consider image with larger height than width
    		}
    	}
     
    }


    import java.awt.Graphics;
    import java.awt.Image;
    import java.awt.image.BufferedImage;
    import java.awt.image.ImageObserver;
    import java.awt.image.Raster;
    import java.io.File;
    import java.io.IOException;
     
    import javax.imageio.ImageIO;
    import javax.swing.JFileChooser;
    import javax.swing.JFrame;
    import javax.swing.filechooser.FileNameExtensionFilter;
     
    public class TransitionTester {
     
    	/**
    	 * @param args
    	 * 
    	 */
     
    	private static BufferedImage img;
     
    	public static void main(String[] args) {
     
    		final int FrameWidth = 400;
    		final int FrameHeight = 500;
    		final int LeftFrameXLeft = 300;
    		final int RightFrameXLeft = LeftFrameXLeft + FrameWidth + 10;
    		final int FrameYTop = 200;
     
    		BufferedImage img = null;
    		BufferedImage rightImage = null;
     
    		//Create left frame with source image
    		JFrame leftFrame = new JFrame("Source Frame");
    		leftFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    		leftFrame.setLocation(LeftFrameXLeft, FrameYTop);
    		leftFrame.setSize(FrameWidth, FrameHeight);
     
    		File imageFile = null;
     
    		boolean imageLoaded=false;
    		while (!imageLoaded) {
    			// Load an image file
    			JFileChooser chooser = new JFileChooser("Hello");
    			FileNameExtensionFilter filter = new FileNameExtensionFilter("JPG & GIF Images", "jpg", "gif");
    			chooser.setFileFilter(filter);
    			int returnVal = chooser.showOpenDialog(leftFrame.getContentPane());
    			if(returnVal == JFileChooser.APPROVE_OPTION) {
    				System.out.println("You chose to open this file: " + chooser.getSelectedFile().getName());
    			}
    			if (returnVal == JFileChooser.CANCEL_OPTION) {
    				leftFrame.dispose();
    				return;
    			}			
     
    			imageFile = chooser.getSelectedFile();
     
    			try {
    				img = ImageIO.read(imageFile);
    			} catch (IOException e) {
    				System.out.println("Error attempting to load image File: " + e);
    				return;
    			}
    			// Reject image if it does not fit in frame
    			imageLoaded = ((img.getWidth() <= FrameWidth) && (img.getHeight() <= FrameHeight));
    			if (!imageLoaded) { System.out.println("Image too large"); }
    		}
    		LeftPanel myLeftPanel = new LeftPanel(img);
    		leftFrame.getContentPane().add(myLeftPanel);
     
    		try {
    			rightImage = ImageIO.read(imageFile);
    		} catch (IOException e) {
    			System.out.println("Error attempting to load image File: " + e);
    			return;
    		}
     
    		RightPanel myRightPanel = new RightPanel(rightImage);
    		myRightPanel.clearImage(myRightPanel.getGraphics());
     
    		// Create right Frame
    		JFrame rightFrame = new JFrame("Destination Frame");
    		rightFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    		rightFrame.setLocation(RightFrameXLeft, FrameYTop);
    		rightFrame.setSize(FrameWidth, FrameHeight);
    		rightFrame.getContentPane().add(myRightPanel);
     
    		leftFrame.setVisible(true);
    		rightFrame.setVisible(true);
     
    		final int NumTransitions = 2;
    		int nextTransition = 0;
    		while(true) {
    			myRightPanel.clearImage(myRightPanel.getGraphics());
    			switch(nextTransition) {
    			case 0: myRightPanel.transitionLRTB(myRightPanel.getGraphics(), img); break;
    			case 1: myRightPanel.transitionDiagonal45LR(myRightPanel.getGraphics(), img); break;
    			}
    			nextTransition = (nextTransition + 1) % NumTransitions;
    		}
    	}
    }

    The part I don't understand is in the RightPanel class. Thank you all very much.


  2. #2
    Super Moderator curmudgeon's Avatar
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    Default Re: What does this part of the code mean?

    Quote Originally Posted by jean28 View Post
    The part I don't understand is in the RightPanel class.
    But you've not posted a RightPanel class.

  3. #3
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    Default Re: What does this part of the code mean?

    Here is the RightPanel code. I need to understand which part of it causes the horizontal and vertical transitions.

    import java.awt.Color;
    import java.awt.Graphics;
    import java.awt.Image;
    import java.awt.image.BufferedImage;
     
    import javax.swing.JPanel;
     
     
    public class RightPanel extends JPanel 
    {
    	private BufferedImage img;
     
    	public RightPanel(BufferedImage img)
    	{
    		this.img = img;
    	}
     
    	public void paintComponent (Graphics g)
    	{
    		super.paintComponent(g);
    		g.drawImage(this.img, 0, 0 , null);		
    	}
     
    	public void clearImage(Graphics g)
    	{
    		int width = img.getWidth();
    		int height = img.getHeight();
    		for (int i=0; i<width; i++)
    		{
    			for (int j=0; j<height; j++)
    			{
    				img.setRGB(i,j,0xffffffff);
    			}
    		}
    	}
     
    	//
    	// Transition by columns top to bottom left to right
    	public void transitionTBLR(Graphics g, BufferedImage leftImage) 
    	{
    		// Lab Q1: Your Code Here
    	}
     
    	//
    	// Transition by rows left to right top to bottom
    	public void transitionLRTB(Graphics g, BufferedImage leftImage) 
    	{
    		int width = leftImage.getWidth();
    		int height = leftImage.getHeight();
    		for (int j=0; j<height; j++)
    		{
    			for (int i=0; i<width; i++)
    			{
    				int pixelColor= leftImage.getRGB(i,j);
    				img.setRGB(i, j, pixelColor);
    			}
    			repaint();
    			try { Thread.sleep(10); } catch (InterruptedException e) { };
    		}
    	}
     
    	//
    	// Transition by diagonals bottom to top left to right
    	public void transitionDiagonal45LR(Graphics g, BufferedImage leftImage)
    	{
    		int width = leftImage.getWidth();
    		int height = leftImage.getHeight();
    		for (int row=0; row<height; row++)
    		{
    			int diagonalRow = row;
    			for (int col=0; col<=row; col++) 
    			{
    				int pixelColor= leftImage.getRGB(col,diagonalRow);
    				img.setRGB(col, diagonalRow, pixelColor);
    				diagonalRow--;
    			}
    			repaint();
    			try { Thread.sleep(10); } catch (InterruptedException e) 
    			{ };
    		}
     
    		if (width > height) 
    		{
    			// Image with larger width than height		
    			for (int i=0; i<(width-height); i++) 
    			{
    				int row = height-1;
    				int col = i+1;
    				for (int j=0; j<height; j++) 
    				{
    					int pixelColor= leftImage.getRGB(col,row);
    					img.setRGB(col, row, pixelColor);
    					col++; row--;
    				}
    				repaint();
    				try { Thread.sleep(10); } catch (InterruptedException e) { };
    			}
     
    			for (int i=0; i<=(width); i++) 
    			{
    				int diagonalRow = height-1;
    				for (int col=(width-height+i); col<width; col++) 
    				{
    					int pixelColor= leftImage.getRGB(col,diagonalRow);
    					img.setRGB(col, diagonalRow, pixelColor);
    					diagonalRow--;
    				}
    				repaint();
    				try { Thread.sleep(10); } catch (InterruptedException e) { };
    			}
    		}
    		else {
    			// Lab Q2: Add code to consider image with larger height than width
    		}
    	}
     
    }

  4. #4
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    Default Re: What does this part of the code mean?

    Basically what I need to know is what set of instructions would make it go from top to bottom and then from left to right.

    This is what I have:

    // Transition by rows left to right top to bottom
    	public void transitionLRTB(Graphics g, BufferedImage leftImage) 
    	{
    		int width = leftImage.getWidth();
    		int height = leftImage.getHeight();
    		for (int j=0; j<height; j++)
    		{
    			for (int i=0; i<width; i++)
    			{
    				int pixelColor= leftImage.getRGB(i,j);
    				img.setRGB(i, j, pixelColor);
    			}
    			repaint();
    			try { Thread.sleep(10); } catch (InterruptedException e) { };
    		}
    	}

    and then I have

    // Transition by diagonals bottom to top left to right
    	public void transitionDiagonal45LR(Graphics g, BufferedImage leftImage)
    	{
    		int width = leftImage.getWidth();
    		int height = leftImage.getHeight();
    		for (int row=0; row<height; row++)
    		{
    			int diagonalRow = row;
    			for (int col=0; col<=row; col++) 
    			{
    				int pixelColor= leftImage.getRGB(col,diagonalRow);
    				img.setRGB(col, diagonalRow, pixelColor);
    				diagonalRow--;
    			}
    			repaint();
    			try { Thread.sleep(10); } catch (InterruptedException e) 
    			{ };
    		}

  5. #5
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    Default Re: What does this part of the code mean?

    Could it be something like this?

    //		int width = leftImage.getWidth();
    //		int height = leftImage.getHeight();
    //		for (int i=0; i<width; i++)
    //		{
    //		for (int j=0; i<width; j++)
    //			{
    //				int pixelColor= leftImage.getRGB(i,j);
    //				img.setRGB(i, j, pixelColor);
    //			}
    //			repaint();
    //			try { Thread.sleep(10); } catch (InterruptedException e) { };
    //		}

  6. #6
    Super Moderator jps's Avatar
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    Default Re: What does this part of the code mean?

    Quote Originally Posted by jean28 View Post
    Basically what I need to know is what set of instructions would make it go from top to bottom and then from left to right
    Yes, I see that: // Lab Q1: Your Code Here
    Doing homework for others is generally frowned upon and considered cheating. I will be happy to answer any questions you have to help you complete the project.



    Quote Originally Posted by jean28 View Post
    Could it be something like this?...
    What did it do when you tried it?

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