在Java中合并2个图像会增加大小

Question

我有两张合并的图像，分别是810KB和850KB大小（Jpegs）。当我使用以下方法时，生成的＆＃39;合并＆＃39; PNG 图片大小为16.4MB（在磁盘上）。为什么会出现这种情况，如何在合并图像为PNG文件的同时缩小尺寸？

public ImageOverlay mergeImage(BufferedImage baseImage, BufferedImage mergeImage, int padding) {
    // create the new image, canvas size is the max. Of both image sizes
    int w = baseImage.getWidth() + padding + mergeImage.getWidth();
    int h = Math.max(baseImage.getHeight(), mergeImage.getHeight());
    BufferedImage combined = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);

    // paint both images, preserving the alpha channels
    Graphics g = combined.getGraphics();
    g.drawImage(baseImage, 0, 0, null);
    g.drawImage(mergeImage, baseImage.getWidth() + padding, 0, null);
    baseImage = combined;
ImageIO.write(baseImage, "png", new File(fileLocation));
}