png图片的读取

一、得到图片中的数据

1、现有一副png图片，提取其中某个区域的内容，保存成另外的图片。

处理后云图如下，黑色的表示云。

现在要得到河南省的的，比如区域的范围是（270,270）到（390,390）的区域。

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.HeadlessException;
import java.awt.Image;
import java.awt.Transparency;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.PixelGrabber;
import java.io.File;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;

public class LoadOneImage {
	public static void main(String[] args) {
		String myreadline = "";
		// 定义一个String类型的变量,用来每次读取一行
		try {

			myreadline = "mask_cloud.png";// 读取一行

			BufferedImage image = toBufferedImage(new ImageIcon("data/Image/"
					+ myreadline).getImage());

			int height = image.getHeight();
			int width = image.getWidth();
			System.out.println("图片的高度为------>" + height);
			System.out.println("图片的宽度为------>" + width);

			// 创建BufferedImage对象
			BufferedImage targetimage = new BufferedImage(1280, 1024,BufferedImage.TYPE_INT_RGB);
			// 获取Graphics2D
			Graphics2D g2d = targetimage.createGraphics();
			// ---------- 增加下面的代码使得背景透明 -----------------
			targetimage = g2d.getDeviceConfiguration().createCompatibleImage(
					1280, 1024, Transparency.TRANSLUCENT);
			// 释放对象
			g2d.dispose();
			g2d = targetimage.createGraphics();
			// ---------- 背景透明代码结束 -----------------

			for (int y = 270; y < 390; y++) {
				for (int x = 270; x < 390; x++) {
					Color color = new Color(image.getRGB(x, y));
					if (color.equals(Color.BLACK))
						g2d.setColor(Color.RED);
					else
						g2d.setColor(Color.BLUE);

					g2d.setStroke(new BasicStroke(1));
					g2d.drawLine(x, y, x, y);

				}

			}

			// 释放对象
			g2d.dispose();

			ImageIO.write(targetimage, "png", new File("test.png"));

		} catch (Exception e) {
			e.printStackTrace();
		}
		System.out.println("结束");
	}

	// This method returns a buffered image with the contents of an image
	public static BufferedImage toBufferedImage(Image image) {
		if (image instanceof BufferedImage) {
			return (BufferedImage) image;
		}

		// Determine if the image has transparent pixels; for this method's
		// implementation, see e661 Determining If an Image Has Transparent
		// Pixels
		boolean hasAlpha = hasAlpha(image);

		// Create a buffered image with a format that's compatible with the
		// screen
		BufferedImage bimage = null;
		GraphicsEnvironment ge = GraphicsEnvironment
				.getLocalGraphicsEnvironment();
		try {
			// Determine the type of transparency of the new buffered image
			int transparency = Transparency.OPAQUE;
			if (hasAlpha) {
				transparency = Transparency.BITMASK;
			}

			// Create the buffered image
			GraphicsDevice gs = ge.getDefaultScreenDevice();
			GraphicsConfiguration gc = gs.getDefaultConfiguration();
			bimage = gc.createCompatibleImage(image.getWidth(null), image
					.getHeight(null), transparency);
		} catch (HeadlessException e) {
			// The system does not have a screen
		}

		if (bimage == null) {
			// Create a buffered image using the default color model
			int type = BufferedImage.TYPE_INT_RGB;
			if (hasAlpha) {
				type = BufferedImage.TYPE_INT_ARGB;
			}
			bimage = new BufferedImage(image.getWidth(null), image
					.getHeight(null), type);
		}

		// Copy image to buffered image
		Graphics g = bimage.createGraphics();
		// Paint the image onto the buffered image
		g.drawImage(image, 0, 0, null);
		g.dispose();

		return bimage;
	}

	// This method returns true if the specified image has transparent pixels
	public static boolean hasAlpha(Image image) {
		// If buffered image, the color model is readily available
		if (image instanceof BufferedImage) {
			BufferedImage bimage = (BufferedImage) image;
			return bimage.getColorModel().hasAlpha();
		}

		// Use a pixel grabber to retrieve the image's color model;
		// grabbing a single pixel is usually sufficient
		PixelGrabber pg = new PixelGrabber(image, 0, 0, 1, 1, false);
		try {
			pg.grabPixels();
		} catch (InterruptedException e) {
		}

		// Get the image's color model
		ColorModel cm = pg.getColorModel();
		return cm.hasAlpha();
	}

}

结果如下：

其中黑色的用红色填充了，白色的用蓝色填充了。