此文章首發於 https://www.jianshu.com/p/394f9b0357b3

最近有個需求，需要App實現群頭像仿微信九宮格排列，由於讓客戶端生成頭像顯示會比較慢，因此只能用服務端實現這個需求,但是網上找都不是很符合要求，於是自己動手改了下實現了該功能:

public final class ImageUtil {

    /**
     * 圖片的間隙
     */
    private static final int SIDE = 6;
    /**
     * 畫板尺寸
     */
    private static final int CANVANS_W = 112;
    private static final int CANVANS_H = 112;

    /**
     * 尺寸1 （小）
     */
    private static final int ONE_IMAGE_SIZE = CANVANS_H - (2 * SIDE);
    /**
     * 尺寸2 （中）
     */
    private static final int TWO_IMAGE_SIZE = (CANVANS_H - (3 * SIDE)) / 2;
    /**
     * 尺寸3 （大）
     */
    private static final int FIVE_IMAGE_SIZE = (CANVANS_H - (4 * SIDE)) / 3;

    private ImageUtil() {
    }

    /**
     * 生成群組頭像
     *
     * @param paths   圖片連結
     * @param dir     輸出路徑
     * @param groupId 群編號
     * @return
     * @throws IOException
     */
    public static boolean getCombinationOfhead(List<String> paths, String dir, String groupId)
            throws IOException {
        List<BufferedImage> bufferedImages = new ArrayList<BufferedImage>();

        int imageSize = 0;
        if (paths.size() <= 1) {
            //若為一張圖片
            imageSize = ONE_IMAGE_SIZE;
        } else if (paths.size() > 1 && paths.size() < 5) {
            //若為2-4張圖片

            imageSize = TWO_IMAGE_SIZE;
        } else {
            //若>=5張圖片
            imageSize = FIVE_IMAGE_SIZE;
        }

        for (int i = 0; i < paths.size(); i++) {
            BufferedImage resize2 = ImageUtil.resize2(paths.get(i), imageSize, imageSize, true);
            bufferedImages.add(resize2);
        }

        BufferedImage outImage = new BufferedImage(CANVANS_W, CANVANS_H, BufferedImage.TYPE_INT_RGB);

        // 生成畫布
        Graphics g = outImage.getGraphics();

        Graphics2D g2d = (Graphics2D) g;

        // 設定背景色
        g2d.setBackground(new Color(231, 231, 231));

        // 通過使用當前繪圖表面的背景色進行填充來清除指定的矩形。
        g2d.clearRect(0, 0, CANVANS_W, CANVANS_H);

        // 開始拼湊 根據圖片的數量判斷該生成那種樣式的組合頭像目前為九種

        for (int i = 1; i <= bufferedImages.size(); i++) {
            Integer size = bufferedImages.size();
            switch (size) {
                case 1:
                    g2d.drawImage(bufferedImages.get(i - 1), SIDE, SIDE, null);
                    break;
                case 2:
                    if (i == 1) {
                        g2d.drawImage(bufferedImages.get(i - 1), SIDE, (CANVANS_W - imageSize) / 2, null);
                    } else {
                        g2d.drawImage(bufferedImages.get(i - 1), 2 * SIDE + imageSize, (CANVANS_W - imageSize) / 2, null);
                    }
                    break;
                case 3:
                    if (i == 1) {
                        g2d.drawImage(bufferedImages.get(i - 1), (CANVANS_W - imageSize) / 2, SIDE, null);
                    } else {
                        g2d.drawImage(bufferedImages.get(i - 1), (i - 1) * SIDE + (i - 2) * imageSize, imageSize + (2 * SIDE), null);

                    }
                    break;
                case 4:

                    if (i <= 2) {
                        g2d.drawImage(bufferedImages.get(i - 1), i * SIDE + (i - 1) * imageSize, SIDE, null);

                    } else {
                        g2d.drawImage(bufferedImages.get(i - 1), (i - 2) * SIDE + (i - 3) * imageSize, imageSize + 2 * SIDE, null);

                    }
                    break;
                case 5:
                    if (i <= 2) {
                        g2d.drawImage(bufferedImages.get(i - 1), (CANVANS_W - 2 * imageSize - SIDE) / 2 + (i - 1) * imageSize + (i - 1) * SIDE, (CANVANS_W - 2 * imageSize - SIDE) / 2, null);

                    } else {
                        g2d.drawImage(bufferedImages.get(i - 1), (i - 2) * SIDE + (i - 3) * imageSize, ((CANVANS_W - 2 * imageSize - SIDE) / 2) + imageSize + SIDE, null);

                    }
//
                    break;
                case 6:
                    if (i <= 3) {
                        g2d.drawImage(bufferedImages.get(i - 1), SIDE * i + imageSize * (i - 1), (CANVANS_W - 2 * imageSize - SIDE) / 2, null);
                    } else {
                        g2d.drawImage(bufferedImages.get(i - 1), ((i - 3) * SIDE) + ((i - 4) * imageSize), ((CANVANS_W - 2 * imageSize - SIDE) / 2) + imageSize + SIDE, null);
                    }
                    break;
                case 7:
                    if (i <= 1) {
                        g2d.drawImage(bufferedImages.get(i - 1), 2 * SIDE + imageSize, SIDE, null);
                    }
                    if (i <= 4 && i > 1) {
                        g2d.drawImage(bufferedImages.get(i - 1), ((i - 1) * SIDE) + ((i - 2) * imageSize), 2 * SIDE + imageSize, null);
                    }
                    if (i <= 7 && i > 4) {
                        g2d.drawImage(bufferedImages.get(i - 1), ((i - 4) * SIDE) + ((i - 5) * imageSize), 3 * SIDE + 2 * imageSize, null);
                    }
                    break;
                case 8:
                    if (i <= 2) {
                        g2d.drawImage(bufferedImages.get(i - 1), (CANVANS_W - 2 * imageSize - SIDE) / 2 + (i - 1) * imageSize + (i - 1) * SIDE, SIDE, null);
                    }
                    if (i <= 5 && i > 2) {
                        g2d.drawImage(bufferedImages.get(i - 1), ((i - 2) * SIDE) + ((i - 3) * imageSize), 2 * SIDE + imageSize, null);
                    }
                    if (i <= 8 && i > 5) {
                        g2d.drawImage(bufferedImages.get(i - 1), ((i - 5) * SIDE) + ((i - 6) * imageSize), 3 * SIDE + 2 * imageSize, null);
                    }
                    break;
                case 9:
                    if (i <= 3) {
                        g2d.drawImage(bufferedImages.get(i - 1), (i * SIDE) + ((i - 1) * imageSize), SIDE, null);
                    }
                    if (i <= 6 && i > 3) {
                        g2d.drawImage(bufferedImages.get(i - 1), ((i - 3) * SIDE) + ((i - 4) * imageSize), 2 * SIDE + imageSize, null);
                    }
                    if (i <= 9 && i > 6) {
                        g2d.drawImage(bufferedImages.get(i - 1), ((i - 6) * SIDE) + ((i - 7) * imageSize), 3 * SIDE + 2 * imageSize, null);
                    }
                    break;
                default:
                    break;
            }
        }

        StringBuffer outPath = new StringBuffer().append(dir)
                .append(File.separatorChar)
                .append("GP-" + groupId).append(".jpg");

        String format = "JPG";
        File file = new File(outPath.toString());
        if (!file.exists()) {
            file.mkdirs();
        }
        return ImageIO.write(outImage, format, file);
    }

  /**
     * 圖片縮放
     *
     * @param filePath 圖片路徑
     * @param height   高度
     * @param width    寬度
     * @param bb       比例不對時是否需要補白
     */
    public static BufferedImage resize2(String filePath, int height, int width,
                                        boolean bb) {
        try {
            double ratio = 0; // 縮放比例
//            System.out.println("圖片縮放"+filePath);
            BufferedImage bi = null;
            if (filePath.indexOf("http://") == 0) {
                bi = ImageIO.read(new URL(filePath));
            } else {
                bi = ImageIO.read(new File(filePath));
            }
            Image itemp = bi.getScaledInstance(width, height,
                    Image.SCALE_SMOOTH);
            // 計算比例
            if ((bi.getHeight() > height) || (bi.getWidth() > width)) {
                if (bi.getHeight() > bi.getWidth()) {
                    ratio = (new Integer(height)).doubleValue()
                            / bi.getHeight();
                } else {
                    ratio = (new Integer(width)).doubleValue() / bi.getWidth();
                }
                AffineTransformOp op = new AffineTransformOp(
                        AffineTransform.getScaleInstance(ratio, ratio), null);
                itemp = op.filter(bi, null);
            }
            if (bb) {
                BufferedImage image = new BufferedImage(width, height,
                        BufferedImage.TYPE_INT_RGB);
                Graphics2D g = image.createGraphics();
                g.setColor(Color.white);
                g.fillRect(0, 0, width, height);
                if (width == itemp.getWidth(null)) {
                    g.drawImage(itemp, 0, (height - itemp.getHeight(null)) / 2,
                            itemp.getWidth(null), itemp.getHeight(null),
                            Color.white, null);
                } else {
                    g.drawImage(itemp, (width - itemp.getWidth(null)) / 2, 0,
                            itemp.getWidth(null), itemp.getHeight(null),
                            Color.white, null);
                }
                g.dispose();
                itemp = image;
            }
            return (BufferedImage) itemp;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 刪除檔案
     * @param path
     * @param filename
     */
    public void delFile(String path, String filename) {
        File file = new File(path + "/" + filename);

        if (file.exists() && file.isFile()) {
            file.delete();
        }
    }

   /**
     * 可依次生成九種情況的群頭像
     *
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        Integer groupId = 0;
        for (int i = 1; i < 10; i++) {
            List<String> list = new ArrayList<>();
            for (int j = 0; j < i; j++) {
                //本地圖片路徑或者網路圖片路徑
                list.add("/Users/Basil/Desktop/1.jpg");
            }
            File file = new File("");
            //生成目錄
            String path = file.getCanonicalPath() + "/src/main/webapp/temp/";
            groupId++;
            ImageUtil.getCombinationOfhead(list, path, groupId.toString());
        }
    }

 

生成的效果圖：

詳細效果圖：