add homework(20150422)

20150422/launch/mydetectnode.launch

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+<launch>
+  <arg name="show_debug_image" default="true" />
+
+  <include file="$(find homework20150422)/launch/camera.launch" />
+
+  <node name="mynode"  pkg="homework20150422" type="mynode.py">
+    <remap from="image" to="camera/image_raw"/>
+    <remap from="twist" to="cmd_vel" />
+    <remap from="debug_image" to="camera/debug_image" />
+  </node>
+
+  <node name="debug_image_viewer" pkg="image_view" type="image_view"
+        if="$(arg show_debug_image)">
+    <remap from="image" to="camera/debug_image" />
+  </node>
+</launch>

20150422/read.md

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+# homework20150422
+
+1. execute `talker/listener` sample
+
+  **Goal:** Comprehend node, topic, publish/subscriber and command line tools for ROS
+
+  - Open new terminal and execute command below:
+  ```bash
+# Terminal 1
+roscore
+```
+  - Open new terminal and execute command below
+  ```bash
+  # Terminal 2
+rosrun homework20150422 talker.l
+```
+  - Open new terminal and execute command below:
+  ```bash
+  # Terminal 3
+rosrun homework20150422 listener.l
+```
+
+  - Open new terminal and execute commands below:
+  ```bash
+  # Terminal 4
+rostopic list # you can find all topics advertised
+rostopic info /chatter # you can see detail information of /chatter topic
+rostopic echo /chatter # you can also see the message published as /chatter topic
+```
+
+2. execute `turtlesim` sample
+
+  **Goal:** Comprehend ros distributed system with multiple launguages, and its launching system called `roslaunch`
+
+  - Open new terminal and execute commands below:
+  ```bash
+  # Terminal 1
+roslaunch homework20150422 turtlesim.launch
+```
+
+  - Focus the terminal and push `up` `down` `right` `left` keys.
+
+  - See what nodes are launching by `rosnode list`:
+  ```bash
+  # Terminal 2
+rosnode list # you can see what nodes are on ROS
+```
+
+  - Now let's take a look at `turtlesim.launch`
+  ```xml
+<launch>
+  <node name="turtlesim_node" pkg="turtlesim" type="turtlesim_node" />
+  <node name="turtlesim_teleop" pkg="roseus" type="roseus"
+        args="$(find homework20150422)/euslisp/turtlesim-teleop.l"
+        output="screen">
+     <remap from="cmd_vel" to="/turtle1/cmd_vel" />
+  </node>
+</launch>
+```
+
+  - You can see 2 `<node></node>` tags in launch file. This means these 2 nodes are launched.:
+  ```xml
+  <node name="turtlesim_node" pkg="turtlesim" type="turtlesim_node" />
+```
+    - `name` attribute: name of the node
+
+  **NOTE** (each node name is already named in each nodes, but once you set name different from that written at original node, it will be overwriten (we call it `remapped`))
+    - `pkg` attribute: package of the node
+    - `type` attribute: program name of the node (we can use each independent node by `rosrun <pkg> <type>`)
+
+  - Now let's look at next node example:
+  ```xml
+  <node name="turtlesim_teleop" pkg="roseus" type="roseus"
+        args="$(find homework20150422)/euslisp/turtlesim-teleop.l"
+        output="screen">
+     <remap from="cmd_vel" to="/turtle1/cmd_vel" />
+  </node>
+```
+    - `args` attribute (optional): arguments passed when launching node
+    - `output` attribute (optional): when this has value `screen`, we can see output log of this node. (This is important when launching nodes on another machine, and need to transmit log output to your terminal)
+    - `<remap from="from_topic" to="to_topic" />`: remapping topic name
+      Detail: `turtlesim-teleop.l` has publisher of `cmd_vel`, so if you launch this node with `rosrun`, this node publishes `/cmd_vel` topic. But, if remapped `cmd_vel` to `/turtle1/cmd_vel` as described above, this node changes the topic name from `/cmd_vel` to `/turtle1/cmd_vel`.
+      You can change subscribe/publish topic of the node without changing any code.
+
+
+3. execute `face_detector` sample:
+
+  **GOAL** Comprehend nested `launch`, topic remapping
+
+  - Open new terminal and execute command below:
+  ```bash
+roslaunch homework20150422 camera.launch
+```
+
+  - You can see the image captured from the camera of your PC
+
+  - Press `Ctrl-C` to stop this launch
+
+  - Open new terminal and execute command below:
+  ```bash
+roslaunch homework20150422 face_detect.launch
+```
+
+  - You can see 2 image_view (one shows raw image view, and another shows the image drawn rectangle over the detected face using OpenCV)
+
+  ```xml
+  <arg name="show_debug_image" default="true" />
+  ...
+  <node name="debug_image_viewer" pkg="image_view" type="image_view"
+        if="$(arg show_debug_image)">
+  ...
+```
+
+  - You can use arguments in launch file
+  - You can also set arguments when launches launch file
+    e.g.: `roslaunch homework20150422 face_detect.launch show_debug_image:=false`
+
+  ```xml
+  <include file="$(find homework20150422)/launch/camera.launch" />
+```
+  - You can include another `launch` files.
+
+4. Make your own image processing node
+
+  - previous `face_detector` example has node doing 3 things:
+    - Subscribe `sensor_msgs/Image` message
+    - Processs image subscribed (detecting face, and draw rectangle on each image)
+    - Publish processed image
+  - Let's make your own node to process image, and visualize processed image
+  - Please send pull request below:
+    - your source codes of image processing that:
+      - Subscribe `sensor_msgs/Image` message
+      - Processs image subscribed (any processing is ok)
+      - Publish processed image
+    - make `launch` file to show following:
+      - original camera image
+      - processed image
+    - add `README` which describes your node
+
+
+---------------------------------------------------
+My homework20150422

20150422/scripts/mynode.py

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+
+import rospy
+
+from sensor_msgs.msg import Image 
+from geometry_msgs.msg import Twist 
+
+from cv_bridge import CvBridge
+
+import cv2 
+
+class mydetect_node(object):
+
+
+    def __init__(self):
+
+        try:
+            self.bridge = CvBridge()
+            self.cascade = cv2.CascadeClassifier(cascade_path)
+        except Exception as e:
+            rospy.logerr("Error: %s" % e)
+        self.image_subscriber = rospy.Subscriber("image", Image, self.image_callback)
+
+        self.face_pose_publisher = rospy.Publisher("twist", Twist)
+        self.debug_image_publisher = rospy.Publisher("debug_image", Image)
+
+    def image_callback(self, msg):
+        img_size = (msg.width, msg.height)
+
+        img_mat = self.bridge.imgmsg_to_cv2(msg)
+
+        img_grey = cv2.cvtColor(img_mat, cv2.cv.CV_BGR2GRAY)
+	img_edge = cv2.Canny(img_grey,100,100)
+
+	pub_debug_img_msg = self.bridge.cv2_to_imgmsg(img_edge, encoding="bgr8")
+	self.debug_image_publisher.publish(pub_debug_img_msg)
+
+if __name__ == '__main__':
+    rospy.init_node("mydetectnode")
+    mydetectnode = mydetect_node()
+
+    rospy.spin()