Java裁剪压缩PNG图片,透明背景色变黑的解决方案

Java裁剪压缩PNG图片,透明背景色变黑

import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Transparency;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;

/**
* 图片工具类
*/
public class ImageUtil {

/**
* 裁剪PNG图片工具类
*
* @param fromFile
*            源文件
* @param toFile
*            裁剪后的文件
* @param outputWidth
*            裁剪宽度
* @param outputHeight
*            裁剪高度
* @param proportion
*            是否是等比缩放
*/
public static void resizePng(File fromFile, File toFile, int outputWidth, int outputHeight,
boolean proportion) {
try {
BufferedImage bi2 = ImageIO.read(fromFile);
int newWidth;
int newHeight;
// 判断是否是等比缩放
if (proportion) {
// 为等比缩放计算输出的图片宽度及高度
double rate1 = ((double) bi2.getWidth(null)) / (double) outputWidth + 0.1;
double rate2 = ((double) bi2.getHeight(null)) / (double) outputHeight + 0.1;
// 根据缩放比率大的进行缩放控制
double rate = rate1 < rate2 ? rate1 : rate2;
newWidth = (int) (((double) bi2.getWidth(null)) / rate);
newHeight = (int) (((double) bi2.getHeight(null)) / rate);
} else {
newWidth = outputWidth; // 输出的图片宽度
newHeight = outputHeight; // 输出的图片高度
}
BufferedImage to = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = to.createGraphics();
to = g2d.getDeviceConfiguration().createCompatibleImage(newWidth, newHeight,
Transparency.TRANSLUCENT);
g2d.dispose();
g2d = to.createGraphics();
@SuppressWarnings("static-access")
Image from = bi2.getScaledInstance(newWidth, newHeight, bi2.SCALE_AREA_AVERAGING);
g2d.drawImage(from, 0, 0, null);
g2d.dispose();
ImageIO.write(to, "png", toFile);
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* 测试
*/
public static void main(String[] args) throws Exception {
File fromFile = new File("c:/wxcking/pic/D77E37CB.png");
File toFile = new File("c:/wxcking/pic/D77E37CB_thumb.png");
resizePng(fromFile, toFile, 100, 100, false);
}
}

java ImageIO.write图片上传变色及背景变黑

public void getImage(HttpServletRequest request, HttpServletResponse response) throws Exception {
       response.setDateHeader("Expires", 0);
       response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
       response.addHeader("Cache-Control", "post-check=0, pre-check=0");
       response.setHeader("Pragma", "no-cache");
       response.setContentType("image/jpeg");
       String uri = request.getRequestURI();
       String imgPath = uri.replace("/ofc/rest/img", "");
       File image = new File(imgPath);
       BufferedImage bi = ImageIO.read(image);
       BufferedImage newBi = resizeImagePng(bi.getWidth(), bi.getHeight(),bi);
       Graphics2D g2d = newBi.createGraphics();
       g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP, 1.0f));
       ServletOutputStream out = response.getOutputStream();
       g2d.drawImage(newBi,0,0,null);
       ImageIO.write(newBi,"png", out);
       //ImageIO.write(bi, "jpg", out);
       //saveAs(bi,"jpg", out);
   }

public static BufferedImage resizeImagePng(int x, int y, BufferedImage bfi) {
       BufferedImage bufferedImage = new BufferedImage(x, y, BufferedImage.TYPE_INT_ARGB);
       bufferedImage.getGraphics().drawImage(
               bfi.getScaledInstance(x, y, Image.SCALE_SMOOTH), 0, 0, null);
       return bufferedImage;
   }

public static void saveAs(BufferedImage image, String formatName, ServletOutputStream outFile) throws IOException {
       if (formatName.equalsIgnoreCase("jpg") || formatName.equalsIgnoreCase("jpeg")) {
           BufferedImage tag = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_BGR);
           Graphics g = tag.getGraphics();
//            Graphics2D gg=tag.createGraphics();
//            tag = gg.getDeviceConfiguration().createCompatibleImage(image.getWidth(), image.getHeight(),Transparency.TRANSLUCENT);
//            gg.dispose();
//            gg = tag.createGraphics();
//            gg.drawImage(image, 0, 0,null);
           g.drawImage(image, 0, 0,image.getWidth(), image.getHeight(),image.getGraphics().getColor(), null); // 绘制缩小后的图
           g.dispose();
           image = tag;
       }
       ImageIO.write(image, formatName, outFile);
   }

来源：https://blog.csdn.net/ya2dan/article/details/49802279