用JAVA处理图片文件
在图片上传时，要进行上传图片的处理，因此整理了一个图片工具类，完成图片的截取。
package image.util;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.WritableRaster;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.imageio.ImageIO;
/**
* 图片工具类，完成图片的截取
*
* @author XXXX created at 2008-6-19
* @since 1.0
* @version
*/
public class ImageHelper {
/**
* 压缩Gif图片
*
* @param source
* 源文件路径
* @param dist
* 目标文件路径
* @param width
* 期望宽度
* @param height
* 期望高度
* @throws Exception
* 异常
*/
public static void resizeGIF(String source, String dist, int width,
int height) throws Exception {
//读入处理的图片
File srcImg = new File(source);
//将图片文件输入IO流
InputStream is = new FileInputStream(srcImg);
//生成一个GifDecoder
GifDecoder gifDecoder = new GifDecoder();
if (GifDecoder.STATUS_FORMAT_ERROR == gifDecoder.read(is)) {//调用read方法读入文件流，出错时，抛出异常。
throw new NotSupportImageFormatException(//自定义的一个异常类。
"The file to be resized is not a valid gif file.");
}
File destImg = new File(dist);
OutputStream os = new FileOutputStream(destImg);
// 动态画面编码器
AnimatedGifEncoder animatedGifEncoder = new AnimatedGifEncoder();
animatedGifEncoder.start(os);
// 设置循环显示的次数
animatedGifEncoder.setRepeat(gifDecoder.getLoopCount());
animatedGifEncoder.setQuality(19);
// 循环得到每一帧
int frameCount = gifDecoder.getFrameCount();
for (int i = 0; i < frameCount; i++) {
BufferedImage sourceFrame = gifDecoder.getFrame(i);
// 缩放
/*
* BufferedImage targetFrame = zoom(sourceFrame, width, height,
* maxWidthLimit, maxHeigthLimit);
*/
BufferedImage targetFrame = resize(sourceFrame, width, height);
// 设置每帧显示间隔时间
animatedGifEncoder.setDelay(gifDecoder.getDelay(i));
animatedGifEncoder.addFrame(targetFrame);
}
animatedGifEncoder.finish();
}
/**
* 判断一个文件类型名称，是否为图片类型
*
* @param fileType
* 文件类型名称
* @return 是PNG, GIF, JPG图片类型为true否则为false
*/
public static boolean isImage(String fileType) {
if (isGif(fileType) || isJpg(fileType) || isPng(fileType))
return true;
else
return false;
}
public static boolean isGif(String fileType) {
if (fileType != null && fileType.trim().equalsIgnoreCase("GIF"))
return true;
else
return false;
}
public static boolean isJpg(String fileType) {
if (fileType != null && fileType.trim().equalsIgnoreCase("JPG"))
return true;
else
return false;
}
public static boolean isPng(String fileType) {
if (fileType != null && fileType.trim().equalsIgnoreCase("PNG"))
return true;
else
return false;
}
/**
* 获取图片文件的文件类型，JPG, PNG, GIF，如果非图片类型那么返回Undefined
*
* @param srcFileName
* 图片全路明
* @return 图片文件类型JPG, PNG, GIF 如果非图片则为Undefined
*/
public static String getImageType(String srcFileName) {
FileInputStream imgFile = null;
byte[] b = new byte[10];
int l = -1;
try {
imgFile = new FileInputStream(srcFileName);
l = imgFile.read(b);
imgFile.close();
} catch (Exception e) {
return "Undefined";
}
if (l == 10) {
byte b0 = b[0];
byte b1 = b[1];
byte b2 = b[2];
byte b3 = b[3];
byte b6 = b[6];
byte b7 = b[7];
byte b8 = b[8];
byte b9 = b[9];
if (b0 == (byte) 'G' && b1 == (byte) 'I' && b2 == (byte) 'F') {
return "GIF";
} else if (b1 == (byte) 'P' && b2 == (byte) 'N' && b3 == (byte) 'G') {
return "PNG";
} else if (b6 == (byte) 'J' && b7 == (byte) 'F' && b8 == (byte) 'I'
&& b9 == (byte) 'F') {
return "JPG";
} else {
return "Undefined";
}
} else {
return "Undefined";
}
}
/**
* JPG文件Resize方法
*
* @param source
* 源文件地址
* @param dist
* 目标文件地址
* @param width
* 目标宽度
* @param height
* 目标高度
* @throws Exception
* 异常信息
*/
public static void resizeJPG(String source, String dist, int width,
int height) throws Exception {
if (!isJpg(getImageType(source)))
throw new Exception(
"The source file is not a jpeg file or not exist!");
BufferedImage sourceImage = ImageIO.read(new File(source));
BufferedImage targetImage = resize(sourceImage, width, height);
ImageIO.write(targetImage, "jpg", new File(dist));
}
/**
* 实现图像的等比缩放
*
* @param source
* @param targetW
* @param targetH
* @return
*/
private static BufferedImage resize(BufferedImage source, int targetW,
int targetH) {
// targetW，targetH分别表示目标长和宽
int type = source.getType();
BufferedImage target = null;
double sx = (double) targetW / source.getWidth();
double sy = (double) targetH / source.getHeight();
// 这里想实现在targetW，targetH范围内实现等比缩放。如果不需要等比缩放
// 则将下面的if else语句注释即可
if (sx < sy) {
// sx = sy;
targetW = (int) (sx * source.getWidth());
} else {
// sy = sx;
targetH = (int) (sy * source.getHeight());
}
if (type == BufferedImage.TYPE_CUSTOM) { // handmade
ColorModel cm = source.getColorModel();
WritableRaster raster = cm.createCompatibleWritableRaster(targetW,
targetH);
boolean alphaPremultiplied = cm.isAlphaPremultiplied();
target = new BufferedImage(cm, raster, alphaPremultiplied, null);
} else
target = new BufferedImage(targetW, targetH, type);
Graphics2D g = target.createGraphics();
// smoother than exlax:
g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BICUBIC);
g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));
g.dispose();
return target;
}
/**
* 实现图像的等比缩放和缩放后的截取
*
* @param inFilePath
* 要截取文件的路径
* @param outFilePath
* 截取后输出的路径
* @param width
* 要截取宽度
* @param hight
* 要截取的高度
* @param proportion
* @throws Exception
*/
public static void saveImageAsJpg(String inFilePath, String outFilePath,
int width, int hight, boolean proportion) throws Exception {
File file = new File(inFilePath);
InputStream in = new FileInputStream(file);
File saveFile = new File(outFilePath);
BufferedImage srcImage = ImageIO.read(in);
if (width > 0 || hight > 0) {
// 原图的大小
int sw = srcImage.getWidth();
int sh = srcImage.getHeight();
// 如果原图像的大小小于要缩放的图像大小，直接将要缩放的图像复制过去
if (sw > width && sh > hight) {
srcImage = resize(srcImage, width, hight);
} else {
String fileName = saveFile.getName();
String formatName = fileName.substring(fileName
.lastIndexOf('.') + 1);
ImageIO.write(srcImage, formatName, saveFile);
return;
}
}
// 缩放后的图像的宽和高
int w = srcImage.getWidth();
int h = srcImage.getHeight();
// 如果缩放后的图像和要求的图像宽度一样，就对缩放的图像的高度进行截取
if (w == width) {
// 计算X轴坐标
int x = 0;
int y = h / 2 - hight / 2;
saveSubImage(srcImage, new Rectangle(x, y, width, hight), saveFile);
}
// 否则如果是缩放后的图像的高度和要求的图像高度一样，就对缩放后的图像的宽度进行截取
else if (h == hight) {
// 计算X轴坐标
int x = w / 2 - width / 2;
int y = 0;
saveSubImage(srcImage, new Rectangle(x, y, width, hight), saveFile);
}
in.close();
}
/**
* 实现缩放后的截图
*
* @param image
* 缩放后的图像
* @param subImageBounds
* 要截取的子图的范围
* @param subImageFile
* 要保存的文件
* @throws IOException
*/
private static void saveSubImage(BufferedImage image,
Rectangle subImageBounds, File subImageFile) throws IOException {
if (subImageBounds.x < 0 || subImageBounds.y < 0
|| subImageBounds.width - subImageBounds.x > image.getWidth()
|| subImageBounds.height - subImageBounds.y > image.getHeight()) {
System.out.println("Bad subimage bounds");
return;
}
BufferedImage subImage = image.getSubimage(subImageBounds.x,
subImageBounds.y, subImageBounds.width, subImageBounds.height);
String fileName = subImageFile.getName();
String formatName = fileName.substring(fileName.lastIndexOf('.') + 1);
ImageIO.write(subImage, formatName, subImageFile);
}
}
这里用到了AnimatedGifEncoder、GifDecoder、LZWEncoder 、NeuQuant类可以从网络上下载，这些是不错的GIF解码和编码操作库。
