dnn/native: add native support for divide

it can be tested with model file generated with below python script:
import tensorflow as tf
import numpy as np
import imageio

in_img = imageio.imread('input.jpg')
in_img = in_img.astype(np.float32)/255.0
in_data = in_img[np.newaxis, :]

x = tf.placeholder(tf.float32, shape=[1, None, None, 3], name='dnn_in')
z1 = 2 / x
z2 = 1 / z1
z3 = z2 / 0.25 + 0.3
z4 = z3 - x * 1.5 - 0.3
y = tf.identity(z4, name='dnn_out')

sess=tf.Session()
sess.run(tf.global_variables_initializer())

graph_def = tf.graph_util.convert_variables_to_constants(sess, sess.graph_def, ['dnn_out'])
tf.train.write_graph(graph_def, '.', 'image_process.pb', as_text=False)

print("image_process.pb generated, please use \
path_to_ffmpeg/tools/python/convert.py to generate image_process.model\n")

output = sess.run(y, feed_dict={x: in_data})
imageio.imsave("out.jpg", np.squeeze(output))

Signed-off-by: Guo, Yejun <yejun.guo@intel.com>

libavfilter/dnn/dnn_backend_native_layer_mathbinary.c

@@ -133,6 +133,23 @@ int dnn_execute_layer_math_binary(DnnOperand *operands, const int32_t *input_ope
             }
         }
         return 0;
+    case DMBO_REALDIV:
+        if (params->input0_broadcast) {
+            for (int i = 0; i < dims_count; ++i) {
+                dst[i] = params->v / src[i];
+            }
+        } else if (params->input1_broadcast) {
+            for (int i = 0; i < dims_count; ++i) {
+                dst[i] = src[i] / params->v;
+            }
+        } else {
+            const DnnOperand *input1 = &operands[input_operand_indexes[1]];
+            const float *src1 = input1->data;
+            for (int i = 0; i < dims_count; ++i) {
+                dst[i] = src[i] / src1[i];
+            }
+        }
+        return 0;
     default:
         return -1;
     }

libavfilter/dnn/dnn_backend_native_layer_mathbinary.h

@@ -34,6 +34,7 @@ typedef enum {
     DMBO_SUB = 0,
     DMBO_ADD = 1,
     DMBO_MUL = 2,
+    DMBO_REALDIV = 3,
     DMBO_COUNT
 } DNNMathBinaryOperation;