ios 裁剪拼装图片

    //1.获取图片
    UIImage *image = [UIImage imageNamed:@"123.jpg"];

    //处理图片
    //2.获取图片的长度
    long length = image.size.width/4;
    
    //3.图片顶点索引
    long indices[] = {
        length * 2,length,//右 right
        0,length,//左 left
        length,0,//上 top
        length,length * 2,//底 bottom
        length,length,//顶 front
        length * 3 ,length,//背面 back
    };
    
    //4.指定图片个数
    //为什么除以2? 包含了x,y
    long faceCount = sizeof(indices)/sizeof(indices[0])/2;
    
    //4.获取图片大小 单个图片大小:length * length ,组合起来:length,length * faceCount
    CGSize imageSize = {length,length * faceCount};
    
    //5.创建基于位图的图形上下文并使其成为当前上下文。
    UIGraphicsBeginImageContext(imageSize);
    
    for (int i = 0; i + 2 <= faceCount * 2 ; i += 2) {
        
        //创建图片,从image.CGImage,获取位置rect上的图片
        CGImageRef CGImage = CGImageCreateWithImageInRect(image.CGImage, CGRectMake(indices[i], indices[i+1], length, length));
        
        //将CGImage转换为UIImage
        UIImage *tmp = [UIImage imageWithCGImage:CGImage];
        
        //绘制图片
        [tmp drawInRect:CGRectMake(0, length * i / 2, length, length)];
        
    }
    
    //5.获取处理好的图片
    //UIGraphicsGetImageFromCurrentImageContext 基于当前位图基于图形上下文的内容返回图像。只有在基于位图的图形上下文是当前图形上下文时，才应该调用此函数。如果目前的情况下是零或没有通过UIGraphicsBeginImageContext创建，这个函数返回nil。
    UIImage *finalImg = UIGraphicsGetImageFromCurrentImageContext();
        //6.保存图片到沙盒
    //指定图片路径
    NSString *path = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:@"image123.png"];
    //获取图片数据-png格式的图片数据
    //UIImagePNGRepresentation(imgData)以PNG格式返回指定图像的数据
    NSData *imageData = UIImagePNGRepresentation(finalImg);
    
    //写入文件
    BOOL writeStatus = [imageData writeToFile:path atomically:YES];
    
    if (writeStatus) {
    
    }else{

    }