bmcv_image_threshold
====================

图像阈值化操作。


**接口形式：**

    .. code-block:: c

        bm_status_t bmcv_image_threshold(
                bm_handle_t handle,
                bm_image input,
                bm_image output,
                unsigned char thresh,
                unsigned char max_value,
                bm_thresh_type_t type);

    其中thresh类型如下：

    .. code-block:: c

        typedef enum {
            BM_THRESH_BINARY = 0,
            BM_THRESH_BINARY_INV,
            BM_THRESH_TRUNC,
            BM_THRESH_TOZERO,
            BM_THRESH_TOZERO_INV,
            BM_THRESH_TYPE_MAX
        } bm_thresh_type_t;



    各个类型对应的具体公式如下：

      .. figure:: ./thresh_type.jpg
         :width: 899px
         :height: 454px
         :scale: 50%
         :align: center


**参数说明：**

* bm_handle_t handle

  输入参数。 bm_handle 句柄。

* bm_image input

  输入参数。输入图像的 bm_image，bm_image 需要外部调用 bmcv_image_create 创建。image 内存可以使用 bm_image_alloc_dev_mem 或者 bm_image_copy_host_to_device 来开辟新的内存，或者使用 bmcv_image_attach 来 attach 已有的内存。

* bm_image output

  输出参数。输出 bm_image，bm_image 需要外部调用 bmcv_image_create 创建。image 内存可以通过 bm_image_alloc_dev_mem 来开辟新的内存，或者使用 bmcv_image_attach 来 attach 已有的内存。如果不主动分配将在 api 内部进行自行分配。

* unsigned char thresh

  阈值。

* max_value

  最大值。

* bm_thresh_type_t type

  阈值化类型。


**返回值说明：**

* BM_SUCCESS: 成功

* 其他:失败


**格式支持：**

该接口目前支持以下 image_format:

+-----+------------------------+------------------------+
| num | input image_format     | output image_format    |
+=====+========================+========================+
| 1   | FORMAT_BGR_PACKED      | FORMAT_BGR_PACKED      |
+-----+------------------------+------------------------+
| 2   | FORMAT_BGR_PLANAR      | FORMAT_BGR_PLANAR      |
+-----+------------------------+------------------------+
| 3   | FORMAT_RGB_PACKED      | FORMAT_RGB_PACKED      |
+-----+------------------------+------------------------+
| 4   | FORMAT_RGB_PLANAR      | FORMAT_RGB_PLANAR      |
+-----+------------------------+------------------------+
| 5   | FORMAT_RGBP_SEPARATE   | FORMAT_RGBP_SEPARATE   |
+-----+------------------------+------------------------+
| 6   | FORMAT_BGRP_SEPARATE   | FORMAT_BGRP_SEPARATE   |
+-----+------------------------+------------------------+
| 7   | FORMAT_GRAY            | FORMAT_GRAY            |
+-----+------------------------+------------------------+
| 8   | FORMAT_YUV420P         | FORMAT_YUV420P         |
+-----+------------------------+------------------------+
| 9   | FORMAT_YUV422P         | FORMAT_YUV422P         |
+-----+------------------------+------------------------+
| 10  | FORMAT_YUV444P         | FORMAT_YUV444P         |
+-----+------------------------+------------------------+
| 11  | FORMAT_NV12            | FORMAT_NV12            |
+-----+------------------------+------------------------+
| 12  | FORMAT_NV21            | FORMAT_NV21            |
+-----+------------------------+------------------------+
| 13  | FORMAT_NV16            | FORMAT_NV16            |
+-----+------------------------+------------------------+
| 14  | FORMAT_NV61            | FORMAT_NV61            |
+-----+------------------------+------------------------+
| 15  | FORMAT_NV24            | FORMAT_NV24            |
+-----+------------------------+------------------------+


目前支持以下 data_type:

+-----+--------------------------------+
| num | data_type                      |
+=====+================================+
| 1   | DATA_TYPE_EXT_1N_BYTE          |
+-----+--------------------------------+


**注意事项：**

1、在调用该接口之前必须确保输入的 image 内存已经申请。

2、input output 的image_format以及data_type必须相同。



**代码示例：**

    .. code-block:: c


        int channel   = 1;
        int width     = 1920;
        int height    = 1080;
        int dev_id    = 0;
        bm_handle_t handle;
        bm_status_t dev_ret = bm_dev_request(&handle, dev_id);
        std::shared_ptr<unsigned char> src_ptr(
                new unsigned char[channel * width * height],
                std::default_delete<unsigned char[]>());
        std::shared_ptr<unsigned char> res_ptr(
                new unsigned char[channel * width * height],
                std::default_delete<unsigned char[]>());
        unsigned char * src_data = src_ptr.get();
        unsigned char * res_data = res_ptr.get();
        for (int i = 0; i < channel * width * height; i++) {
            src_data[i] = rand() % 255;
        }
        // calculate res
        bm_image input, output;
        bm_image_create(handle,
                        height,
                        width,
                        FORMAT_GRAY,
                        DATA_TYPE_EXT_1N_BYTE,
                        &input);
        bm_image_alloc_dev_mem(input);
        bm_image_copy_host_to_device(input, (void **)&src_data);
        bm_image_create(handle,
                        height,
                        width,
                        FORMAT_GRAY,
                        DATA_TYPE_EXT_1N_BYTE,
                        &output);
        bm_image_alloc_dev_mem(output);
        if (BM_SUCCESS != bmcv_image_threshold(handle, input, output, 200, 200, BM_THRESH_BINARY)) {
            std::cout << "bmcv thresh error !!!" << std::endl;
            bm_image_destroy(input);
            bm_image_destroy(output);
            bm_dev_free(handle);
            exit(-1);
        }
        bm_image_copy_device_to_host(output, (void **)&res_data);
        bm_image_destroy(input);
        bm_image_destroy(output);
        bm_dev_free(handle);