Question

我正在尝试使用OpenCL创建一个区域groiwing算法，因为我将使用OpenCV打开一个图像。问题是如何将数据转换为OpenCL。

我在visual studio中使用opencv版本：2.4.9和opencl：AMD APP SDK \ 2.9-1

在使用opencv打开图像后，有人会告诉我该怎么办

Answer 1

通常，有两种方法可以将图像（或任何其他数据）从主机程序传输到OpenCL应用程序中的设备程序：1 - 使用缓冲区2-使用Image2d。它们都使用cl_mem类型。因为使用缓冲区比使用image2d更简单（特别是在灰度图像中），我将解释如何使用OpenCL中的缓冲区将图像从宿主程序传输到设备。

通过openCV对象Mat读取输入图像后，将其转换为灰度图像。然后，我们使用返回clCreateBuffer缓冲区的方法cl_mem。我们可以简单地将data（Mat obeject的属性）传递给clCreateBuffer，以通过输入图像数据初始化输入内核缓冲区。然后我们可以使用clSetKernelArg方法将创建的缓冲区传输到内核。最后，当内核完成其工作时，我们可以通过clEnqueueReadBuffer读取结果。

阅读评论以了解此代码，并毫不犹豫地提出问题。

主机代码：

// Make Contex, Kerenl and other requirements for OpenCL before this section....

Mat image = imread("logo.bmp", CV_LOAD_IMAGE_COLOR); // reading input image by opencv to Mat type
Mat input_; 

cvtColor(image, input_, CV_BGR2GRAY); // convert input image to gray scale 

cl_mem inputSignalBuffer = clCreateBuffer(
        context,
        CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR,
        input_.rows * input_.cols * input_.elemSize(),
        static_cast<void *>(input_.data),               // inputSignalBuffers will be initialized by input_.data which contains input image data
        &errNum);

cl_mem outputSignalBuffer = clCreateBuffer(         // make and preparing an empty output buffer to use after opencl kernel call back
        context,
        CL_MEM_WRITE_ONLY,
        input_.rows * input_.cols * input_.elemSize(),
        NULL,
        &errNum);
    checkErr(errNum, "clCreateBuffer(outputSignal)");


    errNum  = clSetKernelArg(kernel, 0, sizeof(cl_mem), &inputSignalBuffer); // passing input buffer and output buffer to kernel in order to be used on device
    errNum |= clSetKernelArg(kernel, 1, sizeof(cl_mem), &maskBuffer);
    errNum |= clSetKernelArg(kernel, 2, sizeof(cl_mem), &outputSignalBuffer);
    errNum |= clSetKernelArg(kernel, 3, sizeof(cl_uint), &input_.rows);
    errNum |= clSetKernelArg(kernel, 4, sizeof(cl_uint), &input_.cols);
    errNum |= clSetKernelArg(kernel, 5, sizeof(cl_uint), &maskWidth);   

    size_t localWorkSize[2] = { 16, 16 }; // Using 2 dimensional range  with size of work group 16
    size_t globalWorkSize[2] =  { input_.rows,  // Note: Global work size (input image rows and cols) should be multiple of size of work group. 
                                  input_.cols };

    // Queue the kernel up for execution across the array
     errNum = clEnqueueNDRangeKernel( // enqueue kernel with enabling host blocking until finishing kernel execution
        queue, 
        kernel, 
        2, 
        NULL,
        globalWorkSize, 
        localWorkSize,
        0, 
        NULL, 
        NULL);
    checkErr(errNum, "clEnqueueNDRangeKernel");

    Mat output_ = cv::Mat(input_.rows, input_.cols, CV_8UC1);   


    errNum = clEnqueueReadBuffer( //  reading from ourput parameter of kernel 
        queue, 
        outputSignalBuffer, 
        CL_TRUE,
        0, 
        input_.rows * input_.cols * input_.elemSize(), 
        output_.data, //initialize OpenCV Mat by output_.data which contains output results of kernel
        0, 
        NULL, 
        NULL);
    checkErr(errNum, "clEnqueueReadBuffer");

    // cut the extra border spaces which has been added in the first part of the code in order to adjust image size with Work Group Size;   

    cv::imwrite("output.bmp",output_);   // saving output in image file

内核代码：

__kernel void convolve(
    const __global  uchar * const input,
    __constant uint * const mask,   
    __global  uchar * const output,
    const int inputHeight,
    const int inputWidth,
    const int maskWidth)
{    
    uint sum = 0;

    const int curr_x = get_global_id(0); // current curr_x (row) 
    const int curr_y = get_global_id(1); // current curr_y (col)
    int d = maskWidth/2;    

    if(curr_x>d-1 && curr_y>d-1 && curr_x<inputHeight-d && curr_y<inputWidth-d) // checking mask borders not to be out of input matrix 
        for(int i=-d; i<=d; i++)
            for(int j=-d; j<=d; j++) { 
                int mask_ptr = maskWidth*(i+d)+(j+d); //you can also use mad24(maskWidth, i+d, j+d) which is faster.
                sum += input[(curr_x+i)*inputWidth+curr_y+j]*mask[mask_ptr];            
            }

    sum /= (maskWidth*maskWidth); // miangin gereftan

    sum = clamp( sum, (uint)0, (uint)255);// clamp == min(max(x, minval), maxval)

    output[curr_x*inputWidth+curr_y] = sum; 

}

opencl如何使用opencv

1 个答案: