[libcamera-devel] py: examples: Add simple-capture-opencv.py

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diff --git a/src/py/examples/simple-capture-opencv.py b/src/py/examples/simple-capture-opencv.py
new file mode 100755
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+++ b/src/py/examples/simple-capture-opencv.py
@@ -0,0 +1,216 @@ 
+#!/usr/bin/env python3
+
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright (C) 2022, Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
+
+# A simple capture example with opencv. This is almost identical to
+# simple-capture.py, except we use opencv to process and show the image.
+
+import argparse
+import cv2
+import libcamera as libcam
+import libcamera.utils
+import numpy as np
+import selectors
+import sys
+
+# Number of frames to capture
+TOTAL_FRAMES = 100
+
+
+def cartoonify(cvbuf):
+    grayScaleImage = cv2.cvtColor(cvbuf, cv2.COLOR_BGR2GRAY)
+    smoothGrayScale = cv2.medianBlur(grayScaleImage, 5)
+    edgefied = cv2.adaptiveThreshold(smoothGrayScale, 255,
+                                     cv2.ADAPTIVE_THRESH_MEAN_C,
+                                     cv2.THRESH_BINARY, 9, 9)
+    return edgefied
+
+
+def libcam_to_cv(mfb: libcamera.utils.MappedFrameBuffer, cfg: libcam.StreamConfiguration):
+    w = cfg.size.width
+    h = cfg.size.height
+    fmt = cfg.pixel_format
+
+    data = np.array(mfb.planes[0], dtype=np.uint8)
+
+    if fmt == libcam.formats.YUYV:
+        # This is not correct, produces a bluish tint. I didn't find out
+        # what kind of array opencv wants for YUYV.
+        yuyv = data.reshape((h, w // 2 * 4))
+        yuv = np.empty((h, w, 2), dtype=np.uint8)
+        yuv[:, :, 0] = yuyv[:, 0::2]                    # Y
+        yuv[:, :, 1] = yuyv[:, 1::2]                    # UV
+        image = cv2.cvtColor(yuv, cv2.COLOR_YUV2RGB_YUYV)
+    elif fmt == libcam.formats.RGB888:
+        rgb = data.reshape((h, w, 3))
+        rgb[:, :, [0, 1, 2]] = rgb[:, :, [2, 1, 0]]
+        image = rgb
+    elif fmt == libcam.formats.BGR888:
+        rgb = data.reshape((h, w, 3))
+        image = rgb
+    elif fmt == libcam.formats.MJPEG:
+        image = cv2.imdecode(data, cv2.IMREAD_COLOR)
+    else:
+        raise Exception("Unsupported pixel format")
+
+    return image
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-c', '--camera', type=str, default='1',
+                        help='Camera index number (starting from 1) or part of the name')
+    parser.add_argument('-f', '--format', type=str, help='Pixel format')
+    parser.add_argument('-s', '--size', type=str, help='Size ("WxH")')
+    args = parser.parse_args()
+
+    cm = libcam.CameraManager.singleton()
+
+    try:
+        if args.camera.isnumeric():
+            cam_idx = int(args.camera)
+            cam = next((cam for i, cam in enumerate(cm.cameras) if i + 1 == cam_idx))
+        else:
+            cam = next((cam for cam in cm.cameras if args.camera in cam.id))
+    except Exception:
+        print(f'Failed to find camera "{args.camera}"')
+        return -1
+
+    # Acquire the camera for our use
+
+    ret = cam.acquire()
+    assert ret == 0
+
+    # Configure the camera
+
+    cam_config = cam.generate_configuration([libcam.StreamRole.Viewfinder])
+
+    stream_config = cam_config.at(0)
+
+    if args.format:
+        fmt = libcam.PixelFormat(args.format)
+        stream_config.pixel_format = fmt
+
+    if args.size:
+        w, h = [int(v) for v in args.size.split('x')]
+        stream_config.size = libcam.Size(w, h)
+
+    ret = cam.configure(cam_config)
+    assert ret == 0
+
+    print(f'Capturing {TOTAL_FRAMES} frames with {stream_config}')
+
+    stream = stream_config.stream
+
+    # Allocate the buffers for capture
+
+    allocator = libcam.FrameBufferAllocator(cam)
+    ret = allocator.allocate(stream)
+    assert ret > 0
+
+    num_bufs = len(allocator.buffers(stream))
+
+    # Create the requests and assign a buffer for each request
+
+    reqs = []
+    for i in range(num_bufs):
+        # Use the buffer index as the cookie
+        req = cam.create_request(i)
+
+        buffer = allocator.buffers(stream)[i]
+        ret = req.add_buffer(stream, buffer)
+        assert ret == 0
+
+        reqs.append(req)
+
+    # Start the camera
+
+    ret = cam.start()
+    assert ret == 0
+
+    # frames_queued and frames_done track the number of frames queued and done
+
+    frames_queued = 0
+    frames_done = 0
+
+    # Queue the requests to the camera
+
+    for req in reqs:
+        ret = cam.queue_request(req)
+        assert ret == 0
+        frames_queued += 1
+
+    # The main loop. Wait for the queued Requests to complete, process them,
+    # and re-queue them again.
+
+    sel = selectors.DefaultSelector()
+    sel.register(cm.event_fd, selectors.EVENT_READ)
+
+    while frames_done < TOTAL_FRAMES:
+        # cm.get_ready_requests() does not block, so we use a Selector to wait
+        # for a camera event. Here we should almost always get a single
+        # Request, but in some cases there could be multiple or none.
+
+        events = sel.select()
+        if not events:
+            continue
+
+        reqs = cm.get_ready_requests()
+
+        for req in reqs:
+            frames_done += 1
+
+            buffers = req.buffers
+
+            # A ready Request could contain multiple buffers if multiple streams
+            # were being used. Here we know we only have a single stream,
+            # and we use next(iter()) to get the first and only buffer.
+
+            assert len(buffers) == 1
+
+            stream, fb = next(iter(buffers.items()))
+
+            with libcamera.utils.MappedFrameBuffer(fb) as mfb:
+                # Convert the raw buffer to opencv (numpy) buffer
+                image = libcam_to_cv(mfb, stream.configuration)
+
+                # Process the image
+                image = cartoonify(image)
+
+                # Show the image in a window
+                cv2.imshow('Image', image)
+
+                # This one is needed for the opencv to show the window...
+                cv2.waitKey(1)
+
+            meta = fb.metadata
+
+            print("seq {:3}, bytes {}, frames queued/done {:3}/{:<3}"
+                  .format(meta.sequence,
+                          '/'.join([str(p.bytes_used) for p in meta.planes]),
+                          frames_queued, frames_done))
+
+            # If we want to capture more frames we need to queue more Requests.
+            # We could create a totally new Request, but it is more efficient
+            # to reuse the existing one that we just received.
+            if frames_queued < TOTAL_FRAMES:
+                req.reuse()
+                cam.queue_request(req)
+                frames_queued += 1
+
+    # Stop the camera
+
+    ret = cam.stop()
+    assert ret == 0
+
+    # Release the camera
+
+    ret = cam.release()
+    assert ret == 0
+
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())