如何使用Java向图像添加透明填充

Question

我遇到了这个问题： How to scale a Graphics2D image with transparent padding

参考 https://pastebin.com/eFarSKqi

并且我目前正在使用代码，以便可以将其转换为不会重新缩放图像的内容，而只是将其填充。

例如，我有一个500x400像素的图像，那么我需要padd，假设每侧100像素，而无需重新缩放实际图像。

我该怎么做？

用于编辑的基本方法：

public static BufferedImage scaleWithPadding(BufferedImage img, int newWidth, int newHeight) {
    int currentWidth = img.getWidth();
    int currentHeight = img.getHeight();

    int scaledWidth;
    int scaledHeight;
    if (currentWidth == 0 || currentHeight == 0
            || (currentWidth == newWidth && currentHeight == newHeight)) {
        return img;
    } else if (currentWidth == currentHeight) {
        scaledWidth = newWidth;
        scaledHeight = newHeight;
    } else if (currentWidth >= currentHeight) {
        scaledWidth = newWidth;
        double scale = (double) newWidth / (double) currentWidth;
        scaledHeight = (int) Math.round(currentHeight * scale);
    } else {
        scaledHeight = newHeight;
        double scale = (double) newHeight / (double) currentHeight;
        scaledWidth = (int) Math.round(currentWidth * scale);
    }

    int x = (newWidth - scaledWidth) / 2;
    int y = (newHeight - scaledHeight) / 2;
    Color transp = new Color(0, 0, 0, 0);

    BufferedImage newImg = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_ARGB);
    Graphics2D g = newImg.createGraphics();
    g.setColor(transp);
    g.fillRect(0, 0, newWidth, newHeight);
    g.drawImage(img, x, y, x + scaledWidth, y + scaledHeight, 0, 0, currentWidth, currentHeight,
            transp, null);
    g.dispose();

    return newImg;
}