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Java数字图像处理基础


 

  写了很多篇关于图像处理的文章,没有一篇介绍Java 2D的图像处理API,文章讨论和提及的API都是基于JDK6的,首先来看Java中如何组织一个图像对象BufferedImage的,如图:

  一个BufferedImage的像素数据储存在Raster中,ColorModel里面储存颜色空间,类型等信息,当前Java只支持一下三种图像格式- JPG,PNG,GIF,如何向让Java支持其它格式,首先要 完成Java中的图像读写接口,然后打成jar,加上启动参数- Xbootclasspath/p newimageformatIO.jar即可。

  Java中如何读写一个图像文件,使用ImageIO对象即可。读图像文件的代码如下:

  File file = new File("D: estlue_flower.jpg");

  BufferedImage image = ImageIO.read(file);

  写图像文件的代码如下:

  File outputfile = new File("saved.png");

  ImageIO.write(bufferedImage, "png",outputfile);

  从BufferedImage对象中读取像素数据的代码如下:

  1 int type= image.getType();

  2 if ( type ==BufferedImage.TYPE_INT_ARGB || type ==BufferedImage.TYPE_INT_RGB )

  3 return (int [])image.getRaster().getDataElements(x, y, width, height,pixels );

  4 else

  5 return image.getRGB( x, y, width, height, pixels, 0, width );

  首先获取图像类型,如果不是32位的INT型数据,直接读写RGB值即可,否则需要从Raster

  对象中读取。

  往BufferedImage对象中写入像素数据同样遵守上面的规则。代码如下:

  1 int type= image.getType();

  2 if ( type ==BufferedImage.TYPE_INT_ARGB || type ==BufferedImage.TYPE_INT_RGB )

  3 image.getRaster().setDataElements(x, y, width, height, pixels );

  4 else

  5 image.setRGB(x, y, width, height, pixels, 0, width );

  读取图像可能因为图像文件比较大,需要一定时间的等待才可以,Java Advance Image

  Processor API提供了MediaTracker对象来跟踪图像的加载,同步其它操作,使用方法如下:

  MediaTracker tracker = new MediaTracker(this); //初始化对象

  tracker.addImage(image_01, 1); // 加入要跟踪的BufferedImage对象image_001

  tracker.waitForID(1, 10000) // 等待10秒,让iamge_01图像加载

  从一个32位int型数据cARGB中读取图像RGB颜色值的代码如下:

  1 int alpha = (cARGB >> 24)& 0xff; //透明度通道

  2 int red = (cARGB >> 16) &0xff;

  3 int green = (cARGB >> 8) &0xff;

  4 int blue = cARGB & 0xff;

  将RGB颜色值写入成一个INT型数据cRGB的代码如下:

  cRGB = (alpha << 24) | (red<< 16) | (green << 8) | blue;

  创建一个BufferedImage对象的代码如下:

  BufferedImage image = newBufferedImage(256, 256, BufferedImage.TYPE_INT_ARGB);

  一个完整的源代码Demo如下:

  复制代码

  1 package com.gloomyfish.swing;

  2

  3 import java.awt.BorderLayout;

  4 import java.awt.Dimension;

  5 import java.awt.Graphics;

  6 import java.awt.Graphics2D;

  7 import java.awt.RenderingHints;

  8 import java.awt.image.BufferedImage;

  9 import java.io.File;

  10 import java.io.IOException;

  11

  12 import javax.imageio.ImageIO;

  13 import javax.swing.JComponent;

  14 import javax.swing.JFrame;

  15

  16 public class PlasmaDemo extends JComponent {

  17

  18 /**

  19 *

  20 */

  21 private static final long serialVersionUID = -2236160343614397287L;

  22 private BufferedImage image = null;

  23 private int size = 256;

  24

  25 public PlasmaDemo() {

  26 super();

  27 this.setOpaque(false);

  28 }

  29

  30 protected void paintComponent(Graphics g) {

  31 Graphics2D g2 = (Graphics2D)g;

  32 g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

  33 g2.drawImage(getImage(), 5, 5, image.getWidth(), image.getHeight(), null);

  34 }

  35

  36 private BufferedImage getImage() {

  37 if(image == null) {

  38 image = new BufferedImage(size, size,

  BufferedImage.TYPE_INT_ARGB);

  39 int[] rgbData = new int[size*size];

  40 generateNoiseImage(rgbData);

  41 setRGB(image, 0, 0, size, size, rgbData);

  42 File outFile = new File("plasma.jpg");

  43 try {

  44 ImageIO.write(image, "jpg", outFile);

  45 } catch (IOException e) {

  46 e.printStackTrace();

  47 }

  48 }

  49 return image;

  50 }

  51

  52 public void generateNoiseImage(int[] rgbData) {

  53 int index = 0;

  54 int a = 255;

  55 int r = 0;

  56 int g = 0;

  57 int b = 0;

  58

  59 for(int row=0; row

  60 for(int col=0; col

  61 // set random color value for each pixel

  62 r = (int)(128.0 + (128.0 * Math.sin((row + col) / 8.0)));

  63 g = (int)(128.0 + (128.0 * Math.sin((row + col) / 8.0)));

  64 b = (int)(128.0 + (128.0 * Math.sin((row + col) / 8.0)));

  65

  66 rgbData[index] = ((clamp(a) & 0xff) << 24) |

  67 ((clamp(r) & 0xff) << 16) |

  68 ((clamp(g) & 0xff) << 8) |

  69 ((clamp(b) & 0xff));

  70 index++;

  71 }

  72 }

  73

  74 }

  75

  76 private int clamp(int rgb) {

  77 if(rgb > 255)

  78 return 255;

  79 if(rgb < 0)

  80 return 0;

  81 return rgb;

  82 }

  83

  84 public void setRGB( BufferedImage image, int x, int y, int width, int height, int[] pixels ) {

  85 int type = image.getType();

  86 if ( type == BufferedImage.TYPE_INT_ARGB || type == BufferedImage.TYPE_INT_RGB )

  87 image.getRaster().setDataElements( x, y, width, height, pixels );

  88 else

  89 image.setRGB( x, y, width, height, pixels, 0, width );

  90 }

  91

  92 public static void main(String[] args) {

  93 JFrame frame = new JFrame("Noise Art Panel");

  94 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  95 frame.getContentPane().setLayout(new BorderLayout());

  96

  97 // Display the window.

  98 frame.getContentPane().add(new PlasmaDemo(), BorderLayout.CENTER);

  99 frame.setPreferredSize(new Dimension(400 + 25,450));

  100 frame.pack();

  101 frame.setVisible(true);

  102 }

  103 }