Ref: https://blog.csdn.net/zengrenyuan/article/details/80281738
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public static ByteArrayOutputStream encodeWithWaterMark(String content) { if (FRONT_IMAGE == null) { return encode(content); } ByteArrayOutputStream os = null; try { BitMatrix matrix = new QRCodeWriter().encode(content, BarcodeFormat.QR_CODE, WIDTH, HEIGHT); BufferedImage backImage = QRCodeUtils.toBufferedImage(matrix); int fontSize = 20; String stringContent = "邀請QRCode (一般)"; Font font = new Font("Noto Sans TC", Font.PLAIN, fontSize); FontDesignMetrics metrics = FontDesignMetrics.getMetrics(font); int width = getWordWidth(font, stringContent); while (width > WIDTH) { //if string width ＞ image width ➔ use smaller font fontSize = fontSize - 1; font = new Font("Noto Sans TC", Font.PLAIN, fontSize); metrics = FontDesignMetrics.getMetrics(font); width = getWordWidth(font, stringContent); } Graphics2D g = backImage.createGraphics(); g.setFont(font); g.setColor(Color.BLACK); //text-align:center ＆ bottom g.drawString(stringContent, (WIDTH - width) / 2, HEIGHT - metrics.getAscent()); g.dispose(); os = new ByteArrayOutputStream(); if (!ImageIO.write(backImage, IMAGE_FORMAT, os)) { throw new IOException("Could not write an image of format png"); } } catch (Exception e) { LOG.error(Constants.EXCEPTION_PREFIX, e); } return os; } private static BufferedImage toBufferedImage(BitMatrix matrix) { int width = matrix.getWidth(); int height = matrix.getHeight(); BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); for (int x = 0; x < width; x++) { for (int y = 0; y < height; y++) { image.setRGB(x, y, matrix.get(x, y) ? BLACK : WHITE); } } return image; } public static int getWordWidth(Font font, String content) { FontDesignMetrics metrics = FontDesignMetrics.getMetrics(font); int width = 0; for (int i = 0; i < content.length(); i++) { width += metrics.charWidth(content.charAt(i)); } return width; } |