如何在Java中调整图片大小？

Question

您好，我有一个QR码图像，我想调整它的大小，当我尝试使用此代码将其调整为小图像时，我总是得到模糊的图像，并且扫描时QR码不再有效，但是当我使用相同的代码将大小调整为大尺寸图像时，它可以正常工作：

public BufferedImage getScaledInstance(BufferedImage img,
                                   int targetWidth,
                                   int targetHeight,
                                   Object hint,
                                   boolean higherQuality)
{
int type = (img.getTransparency() == Transparency.OPAQUE) ?
    BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage)img;
int w, h;
if (higherQuality) {
    // Use multi-step technique: start with original size, then
    // scale down in multiple passes with drawImage()
    // until the target size is reached
    w = img.getWidth();
    h = img.getHeight();
} else {
    // Use one-step technique: scale directly from original
    // size to target size with a single drawImage() call
    w = targetWidth;
    h = targetHeight;
}

do {
    if (higherQuality && w > targetWidth) {
        w /= 2;
        if (w < targetWidth) {
            w = targetWidth;
        }
    }

    if (higherQuality && h > targetHeight) {
        h /= 2;
        if (h < targetHeight) {
            h = targetHeight;
        }
    }

    BufferedImage tmp = new BufferedImage(w, h, type);
    Graphics2D g2 = tmp.createGraphics();
    g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
    //        g2.setRenderingHint(RenderingHints.KEY_DITHERING, hint);
    g2.drawImage(ret, 0, 0, w, h, null);
    g2.dispose();

    ret = tmp;
} while (w != targetWidth || h != targetHeight);

return ret;
}

有什么问题，我不清楚，请至少给我一个提示，谢谢。

Answer 1

我使用仿射变换来完成此任务，这是我的代码，希望对您有所帮助

/**
 * scale image
 * 
 * @param sbi image to scale
 * @param imageType type of image
 * @param dWidth width of destination image
 * @param dHeight height of destination image
 * @param fWidth x-factor for transformation / scaling
 * @param fHeight y-factor for transformation / scaling
 * @return scaled image
 */
public static BufferedImage scale(BufferedImage sbi, int imageType, int dWidth, int dHeight, double fWidth, double fHeight) {
    BufferedImage dbi = null;
    if(sbi != null) {
        dbi = new BufferedImage(dWidth, dHeight, imageType);
        Graphics2D g = dbi.createGraphics();
        AffineTransform at = AffineTransform.getScaleInstance(fWidth, fHeight);
        g.drawRenderedImage(sbi, at);
    }
    return dbi;
}