Add raw sources and sinks to cscore (#1670)

In some cases, we don't want the cv requirement to get an image, for instance interop with other versions of opencv

This enables getting a raw image, and handling conversions from the user side.

cscore/java-examples/RawCVMatSource.java

@@ -0,0 +1,59 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018-2019 FIRST. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.cscore;
+
+import org.opencv.core.Mat;
+
+import edu.wpi.cscore.VideoMode.PixelFormat;
+
+public class RawCVMatSource extends ImageSource {
+  /**
+   * Create an OpenCV source.
+   *
+   * @param name Source name (arbitrary unique identifier)
+   * @param mode Video mode being generated
+   */
+  public RawCVMatSource(String name, VideoMode mode) {
+    super(CameraServerJNI.createRawSource(name,
+        mode.pixelFormat.getValue(),
+        mode.width,
+        mode.height,
+        mode.fps));
+  }
+
+  /**
+   * Create an OpenCV source.
+   *
+   * @param name Source name (arbitrary unique identifier)
+   * @param pixelFormat Pixel format
+   * @param width width
+   * @param height height
+   * @param fps fps
+   */
+  public RawCVMatSource(String name, VideoMode.PixelFormat pixelFormat, int width, int height, int fps) {
+    super(CameraServerJNI.createRawSource(name, pixelFormat.getValue(), width, height, fps));
+  }
+
+  /**
+   * Put an OpenCV image and notify sinks.
+   *
+   * <p>Only 8-bit single-channel or 3-channel (with BGR channel order) images
+   * are supported. If the format, depth or channel order is different, use
+   * Mat.convertTo() and/or cvtColor() to convert it first.
+   *
+   * @param image OpenCV image
+   */
+  public void putFrame(Mat image) {
+    int channels = image.channels();
+    if (channels != 1 && channels != 3) {
+      throw new VideoException("Unsupported Image Type");
+    }
+    int imgType = channels == 1 ? PixelFormat.kGray.getValue() : PixelFormat.kBGR.getValue();
+    CameraServerJNI.putRawSourceFrame(m_handle, image.dataAddr(), image.width(), image.height(), imgType, (int)image.total() * channels);
+  }
+}