Java实现图片格式转换_java 将jpg格式的图片转jpeg

本文利用java实现将jpg tiff png格式的图片统一转换为png或tiff或jpg的图片，在转换的时候会做图像的resize：

代码实现如下：

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.ByteArrayOutputStream;
 
public class ResizeImageExample {
 
    public static void main(String... args) throws IOException {
        File input = new File("ss-2.png");
        BufferedImage image = ImageIO.read(input);
        BufferedImage resized = resizebyaspect(image, 1655, 2340);
        File output = new File("ss-2-resized-500x500.png");
        ImageIO.write(resized, "png", output);
    }
    // 不按比例缩放
    private static BufferedImage resize(BufferedImage img, int height, int width) {
        Image tmp = img.getScaledInstance(width, height, Image.SCALE_SMOOTH);
        BufferedImage resized = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2d = resized.createGraphics();
        g2d.drawImage(tmp, 0, 0, null);
        g2d.dispose();
        return resized;
    }
    // 按比例缩放
    private static BufferedImage resizebyaspect(BufferedImage img, int height, int width) {
        int ori_width = img.getWidth();
        int ori_height = img.getHeight();
        float ratio_w = (float)width/ori_width;
        float ratio_h = (float)height/ori_height;
        int new_width = (ratio_w < ratio_h) ? width : (int)(ratio_h * ori_width);
        int new_height = (ratio_h < ratio_w) ? height : (int)(ratio_w * ori_height);
        System.out.println(new_height);
        System.out.println(new_width);
        Image tmp = img.getScaledInstance(new_width, new_height, Image.SCALE_SMOOTH);
        BufferedImage resized = new BufferedImage(new_width, new_height, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2d = resized.createGraphics();
        g2d.drawImage(tmp, 0, 0, null);
        g2d.dispose();
        return resized;
    }
}

说明：

1. 输入的图片可以是各种格式

2. 输出的图片也可以是各种格式， 不同的格式修改下面的"png",为"jpg"或其他

ImageIO.write(resized, "png", output);

参考链接：

1. Image transcoding (JPEG to PNG) with Java

2. Java Resize Image to Fixed Width and Height Example