gstreamer/subprojects/gst-python/examples/plugins/python/exampleTransform.py

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#!/usr/bin/python3
# exampleTransform.py
# 2019 Daniel Klamt <graphics@pengutronix.de>
# Inverts a grayscale image in place, requires numpy.
#
# gst-launch-1.0 videotestsrc ! ExampleTransform ! videoconvert ! xvimagesink
import gi
gi.require_version('Gst', '1.0')
gi.require_version('GstBase', '1.0')
gi.require_version('GstVideo', '1.0')
from gi.repository import Gst, GObject, GstBase, GstVideo
import numpy as np
Gst.init(None)
FIXED_CAPS = Gst.Caps.from_string('video/x-raw,format=GRAY8,width=[1,2147483647],height=[1,2147483647]')
class ExampleTransform(GstBase.BaseTransform):
__gstmetadata__ = ('ExampleTransform Python','Transform',
'example gst-python element that can modify the buffer gst-launch-1.0 videotestsrc ! ExampleTransform ! videoconvert ! xvimagesink', 'dkl')
__gsttemplates__ = (Gst.PadTemplate.new("src",
Gst.PadDirection.SRC,
Gst.PadPresence.ALWAYS,
FIXED_CAPS),
Gst.PadTemplate.new("sink",
Gst.PadDirection.SINK,
Gst.PadPresence.ALWAYS,
FIXED_CAPS))
def do_set_caps(self, incaps, outcaps):
struct = incaps.get_structure(0)
self.width = struct.get_int("width").value
self.height = struct.get_int("height").value
return True
def do_transform_ip(self, buf):
try:
with buf.map(Gst.MapFlags.READ | Gst.MapFlags.WRITE) as info:
# Create a NumPy ndarray from the memoryview and modify it in place:
A = np.ndarray(shape = (self.height, self.width), dtype = np.uint8, buffer = info.data)
A[:] = np.invert(A)
return Gst.FlowReturn.OK
except Gst.MapError as e:
Gst.error("Mapping error: %s" % e)
return Gst.FlowReturn.ERROR
GObject.type_register(ExampleTransform)
__gstelementfactory__ = ("ExampleTransform", Gst.Rank.NONE, ExampleTransform)