Function main

compute/example/opencv_flip.cpp:26–101

this example shows how to read an image with OpenCV, transfer the image to the GPU, and apply a simple flip filter written in OpenCL

// this example shows how to read an image with OpenCV, transfer the
// image to the GPU, and apply a simple flip filter written in OpenCL
int main(int argc, char *argv[])
{
    // check command line
    if(argc < 2){
        std::cerr << "usage: " << argv[0] << " FILENAME" << std::endl;
        return -1;
    }

    // read image with opencv
    cv::Mat cv_image = cv::imread(argv[1], CV_LOAD_IMAGE_COLOR);
    if(!cv_image.data){
        std::cerr << "failed to load image" << std::endl;
        return -1;
    }

    // get default device and setup context
    compute::device gpu = compute::system::default_device();
    compute::context context(gpu);
    compute::command_queue queue(context, gpu);

    // convert image to BGRA (OpenCL requires 16-byte aligned data)
    cv::cvtColor(cv_image, cv_image, CV_BGR2BGRA);

    // transfer image to gpu
    compute::image2d input_image =
        compute::opencv_create_image2d_with_mat(
            cv_image, compute::image2d::read_write, queue
        );

    // create output image
    compute::image2d output_image(
        context,
        input_image.width(),
        input_image.height(),
        input_image.format(),
        compute::image2d::write_only
    );

    // create flip program
    const char source[] = BOOST_COMPUTE_STRINGIZE_SOURCE(
        __kernel void flip_kernel(__read_only image2d_t input,
                                  __write_only image2d_t output)
        {
            const sampler_t sampler = CLK_ADDRESS_NONE | CLK_FILTER_NEAREST;
            int height = get_image_height(input);
            int2 input_coord = { get_global_id(0), get_global_id(1) };
            int2 output_coord = { input_coord.x, height - input_coord.y - 1 };
            float4 value = read_imagef(input, sampler, input_coord);
            write_imagef(output, output_coord, value);
        }
    );

    compute::program flip_program =
        compute::program::create_with_source(source, context);
    flip_program.build();

    // create flip kernel and set arguments
    compute::kernel flip_kernel(flip_program, "flip_kernel");