opencl(二十一)----直方图

   计算RGB图像的直方图

// kernel

__kernel void histogram(__global uchar* imgdata,
                        __global uint *histogram,
                        __local uint *local_histogram,
                         uint data_size_item,
                         uint all_byte_size)
{
    // 对局部数据进行初始化
    for(uchar i =0;i<32;i++)
    {
        local_histogram[0]=0;
    }
    barrier(CLK_LOCAL_MEM_FENCE);// 局部同步

    int item_offset = get_global_id(0) * data_size_item *3;
    // 遍历该工作项所处理的数据
    for(int i = item_offset;i<item_offset+data_size_item *3&&i<all_byte_size;i+=3)
    {
        // B
        atomic_inc(local_histogram+imgdata[i]/8+64);
        // G
        atomic_inc(local_histogram+imgdata[i+1]/8+32);
        // R
        atomic_inc(local_histogram+imgdata[i+2]/8);
    }
    barrier(CLK_GLOBAL_MEM_FENCE);  // 全局同步

    // 归并
    int i = get_local_id(0);
    if(i < 96)
    {
       
        atomic_add(histogram+i,local_histogram[i]); 
    }
}

#include <iostream>
#include <opencv2/opencv.hpp>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>

#ifdef  __APPLE__
#include <OpenCL/opencl.h>
#else
#include <CL/cl.h>
#endif

const char histogram_cl_kernel_filename[]= "histogram.cl";

/**
 * 获取设备
 * @return cl_device_id
 */
 cl_device_id getdevice()
{
     cl_platform_id platform;
     cl_device_id  dev;
     int err;

     // 获取一个平台
     err = clGetPlatformIDs(1,&platform,NULL);
     if(err<0)
     {
         perror("获取平台失败！");
         exit(1);
     }
     // 获取一个GPU设备
     err=clGetDeviceIDs(platform,CL_DEVICE_TYPE_GPU,1,&dev,NULL);
     if(err<0)
     {
         perror("获取设备失败！");
         exit(1);
     }
     return dev;
}

/**
 * 创建并编译程序
 * cl_context ctx:上下文
 * cl_device_id dev : 设备
 * filename： 文件名称
 * @return cl_program
 */
 cl_program build_program(cl_context ctx, cl_device_id dev,const char* filename)
{
     cl_program program;
     FILE *program_handle;
     char *program_buffer ,*program_log;
     size_t program_size, log_size;
     int err;

     // 从文件中读取程序内容
     program_handle = fopen(filename,"r");
     if(program_handle == NULL)
     {
         perror("程序文件无法打开！");
         exit(1);
     }
     fseek(program_handle,0,SEEK_END);
     program_size=ftell(program_handle);
     rewind(program_handle);
     program_buffer = (char*)malloc(program_size + 1);
     program_buffer[program_size] = '';
     fread(program_buffer, sizeof(char), program_size, program_handle);
     fclose(program_handle);

     // 创建 cl_program;
     program = clCreateProgramWithSource(ctx,1,(const char **)&program_buffer,&program_size,&err);
     if(err<0)
     {
         perror("创建cl_program失败！");
         exit(1);
     }
     free(program_buffer);

     // 编译 cl_program
     err = clBuildProgram(program,0,NULL,NULL,NULL,NULL);
     if(err<0)
     {
         // 编译失败获取 失败信息
         clGetProgramBuildInfo(program,dev,CL_PROGRAM_BUILD_LOG,0,NULL,&log_size);
         program_log = (char*)malloc(log_size+1);
         program_log[log_size]='';
         clGetProgramBuildInfo(program,dev,CL_PROGRAM_BUILD_LOG,log_size+1,program_log,NULL);
         std::cout<<"program_log:
 "<<program_log<<std::endl;
         free(program_log);
         exit(1);
     }

     return program;
}

void calhistogram()
{
     int err;
     // 获取设备
     cl_device_id device = getdevice();
     // 创建上下文
     cl_context  context = clCreateContext(NULL, 1, &device, NULL, NULL, &err);
     if(err<0)
     {
         perror("创建上下文失败！");
         exit(1);
     }
     // 创建并编译程序
     cl_program program = build_program(context,device,histogram_cl_kernel_filename);

     // 创建内核
     cl_kernel kernel = clCreateKernel(program,"histogram",&err);

     // 创建缓存对象
     // 读取图片数据
     cv::Mat img = cv::imread("7.jpg");
     unsigned char * data = img.data;
     unsigned int size = img.cols*img.rows*3;
     std::cout<<"字节数：="<<size<<std::endl;
    std::cout<<"像素点数：="<<img.cols*img.rows<<std::endl;
     cl_mem imgdata = clCreateBuffer(context,CL_MEM_READ_ONLY|CL_MEM_COPY_HOST_PTR,size,(void *)data,&err);
     if(err<0)
     {
         std::cout<<err<<std::endl;
         perror("创建图像缓存对象失败！");
         exit(1);
     }

     unsigned int result[96]={0};
     cl_mem result_buffer = clCreateBuffer(context,CL_MEM_READ_WRITE|CL_MEM_COPY_HOST_PTR,sizeof(result),result,NULL);

     // 获取 CU 的个数
     unsigned int size_CU =0;
     clGetDeviceInfo(device, CL_DEVICE_MAX_COMPUTE_UNITS,
                    sizeof(size_CU), &size_CU, NULL);
     std::cout<<"计算单元(CU)的个数为： "<<size_CU<<std::endl;
     // 获取每个工作组中工作项的 数量限制
     size_t item_size_per_group =0;
     clGetDeviceInfo(device,CL_DEVICE_MAX_WORK_GROUP_SIZE,sizeof(item_size_per_group),&item_size_per_group,NULL);
     std::cout<<"每个工作组中工作的最大数量为： "<<item_size_per_group<<std::endl;
     // 工作项的总个数
     size_t item_num = size_CU*item_size_per_group;
     std::cout<<"工作项的总个数为："<<item_num<<std::endl;
     // 每个工作项负的 点个数
     unsigned int  size_per_item = img.cols*img.rows/item_num +1;
     std::cout<<"每个工作项负责的点数为："<<size_per_item<<std::endl;

     // 设置核参数
     err  = clSetKernelArg(kernel,0,sizeof(imgdata),&imgdata);  // 图像数据
     err |= clSetKernelArg(kernel,1,sizeof(result_buffer),&result_buffer); // 存储结果的地址
     err |= clSetKernelArg(kernel,2,sizeof(result),NULL);  // 局部结果
     err |= clSetKernelArg(kernel,3,sizeof(size_per_item),&size_per_item); // 每个项处理的数据点数大小
     err |= clSetKernelArg(kernel,4,sizeof(size),&size);
     if(err<0)
     {
         perror("设置参数失败！");
         exit(1);
     }
     // 创建命令队列
     cl_command_queue queue = clCreateCommandQueue(context, device , 0 ,&err);
     if(err<0)
     {
         perror("创建命令队列失败！");
         exit(1);
     }

     size_t offset =0;
     err = clEnqueueNDRangeKernel(queue,kernel,1,&offset,&item_num, &item_size_per_group,0,NULL,NULL);
     if(err<0)
     {
         perror("Enqueue the kernel failed!");
         exit(1);
     }
     // 读取结果命令
     err = clEnqueueReadBuffer(queue,result_buffer,CL_TRUE,0,sizeof(result),&result,0,NULL,NULL);
     if(err<0)
     {
         perror("读取结果失败！");
         exit(1);
     }
     // 输出结果
     // R
    int temp=0;
     for(int i=0;i<32;i++)
     {
         temp+=result[i];
         std::cout<<i*8<<"---"<<(i+1)*8-1<<":"<<result[i]<<std::endl;
     }
     std::cout<<temp<<std::endl;
}

int main()
{
    std::cout << "Hello, World!" << std::endl;
    calhistogram();
    return 0;
}