使用的是暴力拼接(从左向右，从上到下，先放矮的图片进去)
对于后缀为_strip[数字]的图片会再次分割提高图集密度
效果
拼接前

拼接后

对应子图的偏移信息记录类(自动生成)

单张图片信息类(可能有多张图片因为有后面名为_strip[数字]的情况)

public class ImageInfo implements Comparable<ImageInfo>{

    private int[] xs;
    private int[] ys;
    private int index;
    private int width;
    private int height;
    private int num;
    private String name;
    private BufferedImage image;
    private static final Pattern NAME_COMPILE = Pattern.compile("(.*)_strip(\\d+)\\.");

    public ImageInfo(File file) throws IOException {
        initNameAndNum(file.getName());
        initImage(file);
    }

    private void initImage(File file) throws IOException {
        image= ImageIO.read(file);
        width= image.getWidth()/num;
        height=image.getHeight();
    }

    private void initNameAndNum(String fullName) {
        Matcher matcher = NAME_COMPILE.matcher(fullName);
        if(matcher.find()){
            name=matcher.group(1);
            num=Integer.parseInt(matcher.group(2));
        }else {
            name=fullName.substring(0,fullName.lastIndexOf('.'));
            num=1;
        }
        xs=new int[num];
        ys=new int[num];
        index=0;
    }

    public boolean hasSetAll(){
        return index==num;
    }

    public int getWidth() {
        return width;
    }

    public int getHeight() {
        return height;
    }

    @Override
    public int compareTo(ImageInfo tar) {
        return tar.height-this.height;
    }

    public void setPos(int x, int y) {
        xs[index]=x;
        ys[index]=y;
        index++;
    }

    public void processSelf(Graphics g, ClassMaker classMaker) {
        g.drawImage(image,xs[index],ys[index],xs[index]+width,ys[index]+height,index*width,
                0,(index+1)*width,height,null);
        String name=this.name;
        if(num>1){
            name+=index;
        }
        classMaker.addInfo(xs[index],ys[index],xs[index]+width,ys[index]+height,name);
        index++;
    }

    public void reset() {
        index=0;
    }

}

单个图集信息(可能数据量太大，打出多个图集)

public class BigImage {

    private List<ImageInfo> imageInfos;
    private int width;
    private int height;
    private int x;
    private int y;
    private int offsetH;

    public BigImage(int width, int height) {
        this.width = width;
        this.height = height;
        initData();
    }

    private void initData() {
        x=0;
        y=0;
        offsetH=0;
        imageInfos=new ArrayList<>();
    }

    public boolean addImage(ImageInfo imageInfo) {
        if(offsetH==0)offsetH=imageInfo.getHeight();
        while (y+imageInfo.getHeight()<=height){
            if(x+imageInfo.getWidth()>width){
                y+=offsetH;
                x=0;
                offsetH=imageInfo.getHeight();
            }else {//横向放入
                imageInfo.setPos(x,y);
                imageInfos.add(imageInfo);
                x+=imageInfo.getWidth();
                return true;
            }
        }
        return false;
    }

    public void processImage(String tarPath, int index, ClassMaker classMaker) throws IOException {
        BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_4BYTE_ABGR);
        Graphics g = image.getGraphics();
        String fileName="create_"+index+".png";
        classMaker.setImageName(fileName);
        for (ImageInfo imageInfo:imageInfos){
            imageInfo.processSelf(g,classMaker);
        }
        ImageIO.write(image,"png",new File(tarPath,fileName));
    }

}

主处理类

public class ImageProcessor {

    public static void main(String[] args) throws IOException {
                    //      资源目录                    目标目录                  图集大小
        processImage("src/testGame/res","src/testGame/tar",1024,1024);
    }

    private static void processImage(String srcPath,String tarPath, int width, int height) throws IOException {
        File[] files = new File(srcPath).listFiles();
        ImageInfo[] imageInfos=new ImageInfo[files.length];
        for (int i = 0; i < imageInfos.length; i++) {
            imageInfos[i]=new ImageInfo(files[i]);
        }
        Arrays.sort(imageInfos);
        putBigImage(imageInfos,width,height,tarPath);
    }

    private static void putBigImage(ImageInfo[] imageInfos, int width, int height,String tarPath) throws IOException {
        Stack<BigImage> stack=new Stack<>();
        stack.push(new BigImage(width,height));
        int index=0;
        while (index<imageInfos.length){
            while (!imageInfos[index].hasSetAll()){
                if(!stack.peek().addImage(imageInfos[index])){
                    stack.push(new BigImage(width,height));
                }
            }
            imageInfos[index].reset();
            index++;
        }
        index=0;
        ClassMaker classMaker = new ClassMaker();
        while (!stack.isEmpty()){
            stack.pop().processImage(tarPath,index++,classMaker);
        }
        classMaker.create(tarPath);
    }

}

资源类生成器

public class ClassMaker {

    private List<Integer> x1s;
    private List<Integer> y1s;
    private List<Integer> x2s;
    private List<Integer> y2s;
    private List<String> names;
    private List<String> imageNames;
    private String imageName;

    public ClassMaker() {
        initData();
    }

    public void setImageName(String imageName) {
        this.imageName = imageName;
    }

    private void initData() {
        x1s=new ArrayList<>();
        y1s=new ArrayList<>();
        x2s=new ArrayList<>();
        y2s=new ArrayList<>();
        names=new ArrayList<>();
        imageNames=new ArrayList<>();
    }

    public void addInfo(int x1,int y1,int x2,int y2,String name){
        x1s.add(x1);
        y1s.add(y1);
        x2s.add(x2);
        y2s.add(y2);
        names.add(name);
        imageNames.add(imageName);
    }

    public void create(String tarPath) throws IOException {
        String classContent=buildContent();
        FileOutputStream out = new FileOutputStream(tarPath + "/Res.java");
        out.write(classContent.getBytes());
        out.close();
    }

    private String buildContent() {
        StringBuilder builder = new StringBuilder("package testGame.tar;\n\npublic final class Res {\n\n");
        builderInt(builder,x1s,"x1s");
        builderInt(builder,y1s,"y1s");
        builderInt(builder,x2s,"x2s");
        builderInt(builder,y2s,"y2s");
        builderString(builder);
        builder.append("\n");
        for (int i=0;i<names.size();i++){
            builder.append("\tpublic final static int ").append(names.get(i)).append("=").append(i)
                    .append(";\n");
        }
        builder.append("\n}");
        return builder.toString();
    }

    private void builderString(StringBuilder builder) {
        builder.append("\tpublic final static String[] imageNames={");
        for (String imageName:imageNames){
            builder.append("\"").append(imageName).append("\",");
        }
        builder.append("};\n");
    }

    private void builderInt(StringBuilder builder, List<Integer> nums,String name) {
        builder.append("\tpublic final static int[] ").append(name).append("={");
        for (Integer integer:nums){
            builder.append(integer).append(",");
        }
        builder.append("};\n");
    }

    @Override
    public String toString() {
        return "ClassMaker{" +
                "x1s=" + x1s +
                ", \ny1s=" + y1s +
                ", \nx2s=" + x2s +
                ", \ny2s=" + y2s +
                ", \nnames=" + names +
                ", \nimageNames=" + imageNames +
                ", \nimageName='" + imageName + '\'' +
                '}';
    }

}

对于太过极端的不太适合，要设置合适的图集大小，若设置的宽度太小可能造成死循环