调整 Java BufferedImage 的大小，保持纵横比并填充背景

Question

我正在使用 Java 来存储和修改 .jpg 图像（不是 Android 或 Swing）。 如果新尺寸与原始图像不成比例，我想转换具有新尺寸的图像以保持纵横比并用白色填充背景。

 BufferedImage image = /*Here i read from disk and load the image */;
 image = resizeImage(image,  newWidth, newHeight);
 ImageIO.write(image, extension, new File(filename + "_" + page + "." + extension));

我试图实现的功能是 resizeImage：在示例中调整图像大小，但它不保持纵横比。

  private static BufferedImage resizeImage(BufferedImage originalImage, int width, int height) {
        BufferedImage resizedImage = new BufferedImage(width, height, originalImage.getType());
        Graphics2D g = resizedImage.createGraphics();
        g.drawImage(originalImage, 0, 0, width, height, null);
        g.dispose();
        return resizedImage;
    }

我认为一张图片将更能说明我的要求：

如果原始图像是 200x200 并且被要求将大小调整为 400x300，则结果应该是带有白边的图片，并且原始图片的大小在内部进行了调整。 在此示例中应为 300x300。

问题不在于如何调整大小，而在于如何用白色填充剩余的图像，并将原始调整大小的图像放在它的中心。

Answer 1

这段代码对我有用：

private static BufferedImage resizeImage(BufferedImage originalImage, int newWidth, int newHeight) {
    BufferedImage resizedImage = new BufferedImage(newWidth, newHeight, originalImage.getType());
    Graphics2D graphics = resizedImage.createGraphics();
    graphics.setColor(Color.WHITE);
    // fill the entire picture with white
    graphics.fillRect(0, 0, newWidth, newHeight);
    int maxWidth = 0;
    int maxHeight = 0;
    // go along the width and height in increments of 1 until one value is equal to the specified resize value
    while (maxWidth <= newWidth && maxHeight <= newHeight)
    {
        ++maxWidth;
        ++maxHeight;
    }
    // calculate the x value with which the original image is centred
    int centerX = (resizedImage.getWidth() - maxWidth) / 2;
    // calculate the y value with which the original image is centred
    int centerY = (resizedImage.getHeight() - maxHeight) / 2;
    // draw the original image
    graphics.drawImage(originalImage, centerX, centerY, maxWidth, maxHeight, null);
    graphics.dispose();
    return resizedImage;
}

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