需求:
有一个列表加载封面图片 , 只做一个封面显示 , 无实际观察意义,但是图片的原图很大 , 造成资源加载浪费,所以按照比例压缩文件
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGEncodeParam;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
/**
* 文件读取工具类
*/
public class FileUtil {
/**
* 读取文件内容，作为字符串返回
*/
public static String readFileAsString(String filePath) throws IOException {
File file = new File(filePath);
if (!file.exists()) {
throw new FileNotFoundException(filePath);
}
if (file.length() > 1024 * 1024 * 1024) {
throw new IOException("File is too large");
}
StringBuilder sb = new StringBuilder((int) (file.length()));
// 创建字节输入流
FileInputStream fis = new FileInputStream(filePath);
// 创建一个长度为10240的Buffer
byte[] bbuf = new byte[10240];
// 用于保存实际读取的字节数
int hasRead = 0;
while ((hasRead = fis.read(bbuf)) > 0) {
sb.append(new String(bbuf, 0, hasRead));
}
fis.close();
return sb.toString();
}
/**
* 根据文件路径读取byte[] 数组
*/
public static byte[] readFileByBytes(String filePath) throws IOException {
File file = new File(filePath);
if (!file.exists()) {
throw new FileNotFoundException(filePath);
} else {
ByteArrayOutputStream bos = new ByteArrayOutputStream((int) file.length());
BufferedInputStream in = null;
try {
in = new BufferedInputStream(new FileInputStream(file));
short bufSize = 1024;
byte[] buffer = new byte[bufSize];
int len1;
while (-1 != (len1 = in.read(buffer, 0, bufSize))) {
bos.write(buffer, 0, len1);
}
byte[] var7 = bos.toByteArray();
return var7;
} finally {
try {
if (in != null) {
in.close();
}
} catch (IOException var14) {
var14.printStackTrace();
}
bos.close();
}
}
}
/**
* 直接指定压缩后的宽高：
* (先保存原文件，再压缩、上传)
* 壹拍项目中用于二维码压缩
*
* @param oldFile 要进行压缩的文件全路径
* @param width 压缩后的宽度
* @param height 压缩后的高度
* @param quality 压缩质量
* @param smallIcon 文件名的小小后缀(注意，非文件后缀名称),入压缩文件名是yasuo.jpg,则压缩后文件名是yasuo(+smallIcon).jpg
* @return 返回压缩后的文件的全路径
*/
public static String zipImageFile(String oldFile, int width, int height,
float quality, String smallIcon) {
if (oldFile == null) {
return null;
}
String newImage = null;
try {
Image srcFile = ImageIO.read(new File(oldFile));
// 宽,高设定
BufferedImage tag = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
tag.getGraphics().drawImage(srcFile, 0, 0, width, height, null);
String filePrex = oldFile.substring(0, oldFile.indexOf('.'));
/* 压缩后的文件名 */
newImage = filePrex + smallIcon + oldFile.substring(filePrex.length());
/* 压缩之后临时存放位置 */
FileOutputStream out = new FileOutputStream(newImage);
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
JPEGEncodeParam jep = JPEGCodec.getDefaultJPEGEncodeParam(tag);
/* 压缩质量 */
jep.setQuality(quality, true);
encoder.encode(tag, jep);
out.close();
} catch (IOException e) {
e.printStackTrace();
}
return newImage;
}
/**
* 保存文件到服务器临时路径(用于文件上传)
*
* @param fileName 文件名称
* @param is 流信息
* @return 文件全路径
*/
public static String writeFile(String fileName, InputStream is) {
if (fileName == null || fileName.trim().length() == 0) {
return null;
}
try {
FileOutputStream fos = new FileOutputStream(fileName);
byte[] readBytes = new byte[512];// 缓冲大小
int readed;
while ((readed = is.read(readBytes)) > 0) {
fos.write(readBytes, 0, readed);
}
fos.close();
is.close();
} catch (IOException e) {
e.printStackTrace();
}
return fileName;
}
/**
* 等比例压缩算法：
* 算法思想：根据压缩基数和压缩比来压缩原图，生产一张图片效果最接近原图的缩略图
*
* @param srcURL 原图地址
* @param deskURL 缩略图地址
* @param comBase 压缩基数
* @param scale 压缩限制(宽/高)比例 一般用1：
* 当scale>=1,缩略图height=comBase,width按原图宽高比例;若scale<1,缩略图width=comBase,height按原图宽高比例
* @throws Exception 异常信息
*/
public static void saveMinPhoto(String srcURL, String deskURL, double comBase,
double scale) throws Exception {
File srcFile = new java.io.File(srcURL);
Image src = ImageIO.read(srcFile);
int srcHeight = src.getHeight(null);
int srcWidth = src.getWidth(null);
int deskHeight = 0;// 缩略图高
int deskWidth = 0;// 缩略图宽
double srcScale = (double) srcHeight / srcWidth;
/*缩略图宽高算法*/
if ((double) srcHeight > comBase || (double) srcWidth > comBase) {
if (srcScale >= scale || 1 / srcScale > scale) {
if (srcScale >= scale) {
deskHeight = (int) comBase;
deskWidth = srcWidth * deskHeight / srcHeight;
} else {
deskWidth = (int) comBase;
deskHeight = srcHeight * deskWidth / srcWidth;
}
} else {
if ((double) srcHeight > comBase) {
deskHeight = (int) comBase;
deskWidth = srcWidth * deskHeight / srcHeight;
} else {
deskWidth = (int) comBase;
deskHeight = srcHeight * deskWidth / srcWidth;
}
}
} else {
deskHeight = srcHeight;
deskWidth = srcWidth;
}
BufferedImage tag = new BufferedImage(deskWidth, deskHeight, BufferedImage.TYPE_3BYTE_BGR);
tag.getGraphics().drawImage(src, 0, 0, deskWidth, deskHeight, null); //绘制缩小后的图
FileOutputStream deskImage = new FileOutputStream(deskURL); //输出到文件流
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(deskImage);
encoder.encode(tag); //近JPEG编码
deskImage.close();
}
public static void main(String[] args) throws Exception {
FileUtil.saveMinPhoto("C:\\Users\\18701\\Desktop\\1589463294(1).jpg", "D:/12.jpg", 139, 0.9d);
}
}