/**
	 * 调整bufferedimage大小
	 * @param source BufferedImage 原始image
	 * @param targetW int  目标宽
	 * @param targetH int  目标高
	 * @param flag boolean 是否同比例调整
	 * @return BufferedImage  返回新image
	 */
	private static BufferedImage resizeBufferedImage(BufferedImage source, int targetW, int targetH, boolean flag) {
		int type = source.getType();
		BufferedImage target = null;
		double sx = (double) targetW / source.getWidth();
		double sy = (double) targetH / source.getHeight();
		if (flag && sx > sy) {
			sx = sy;
			targetW = (int) (sx * source.getWidth());
		} else if(flag && sx <= sy){
			sy = sx;
			targetH = (int) (sy * source.getHeight());
		}
		if (type == BufferedImage.TYPE_CUSTOM) { // handmade
			ColorModel cm = source.getColorModel();
			WritableRaster raster = cm.createCompatibleWritableRaster(targetW, targetH);
			boolean alphaPremultiplied = cm.isAlphaPremultiplied();
			target = new BufferedImage(cm, raster, alphaPremultiplied, null);
		} else {
			target = new BufferedImage(targetW, targetH, type);
		}
		Graphics2D g = target.createGraphics();
		g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
		g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));
		g.dispose();
		return target;
	}

写二维码生成的时候碰到的问题，二维码生成时有个版本号（取值为0-40），版本号越大尺寸越大，可存储的信息越大，相对应的二维码也会越密。

所以想到生成原始的二维码，合成海报时将该二维码放大。

调整图片大小代码如上。（转自网络）