Java图像调整大小，保持纵横比

Question

我有一张要调整大小的图片:

if((width != null) || (height != null))
{
    try{
        // scale image on disk
        BufferedImage originalImage = ImageIO.read(file);
        int type = originalImage.getType() == 0? BufferedImage.TYPE_INT_ARGB
                                               : originalImage.getType();

        BufferedImage resizeImageJpg = resizeImage(originalImage, type, 200, 200);
        ImageIO.write(resizeImageJpg, "jpg", file); 

       } catch(IOException e) {
           System.out.println(e.getMessage());
       }
}

这是我调整图像大小的方式:

private static BufferedImage resizeImage(BufferedImage originalImage, int type,
                                         Integer img_width, Integer img_height)
{
    BufferedImage resizedImage = new BufferedImage(img_width, img_height, type);
    Graphics2D g = resizedImage.createGraphics();
    g.drawImage(originalImage, 0, 0, img_width, img_height, null);
    g.dispose();

    return resizedImage;
}

现在的问题是，我还需要保持纵横比。也就是说，我需要新的 200/200 图像来包含缩放的新图像。像这样的东西:

我尝试了一些方法，但效果不如预期。任何帮助表示赞赏。非常感谢。

Answer 1

我们开始吧:

Dimension imgSize = new Dimension(500, 100);
Dimension boundary = new Dimension(200, 200);

根据边界返回新尺寸的函数:

public static Dimension getScaledDimension(Dimension imgSize, Dimension boundary) {

    int original_width = imgSize.width;
    int original_height = imgSize.height;
    int bound_width = boundary.width;
    int bound_height = boundary.height;
    int new_width = original_width;
    int new_height = original_height;

    // first check if we need to scale width
    if (original_width > bound_width) {
        //scale width to fit
        new_width = bound_width;
        //scale height to maintain aspect ratio
        new_height = (new_width * original_height) / original_width;
    }

    // then check if we need to scale even with the new height
    if (new_height > bound_height) {
        //scale height to fit instead
        new_height = bound_height;
        //scale width to maintain aspect ratio
        new_width = (new_height * original_width) / original_height;
    }

    return new Dimension(new_width, new_height);
}

如果有人还需要图像大小调整代码，here is a decent solution .

如果您不确定上述解决方案，there are different ways达到同样的效果。