高通滤波器: 通过检测图像的某个区域，然后根据像素与周围像素的亮度差值来提升该像素的亮度的滤波器，在计算完中央像素与周围邻近像素的亮度差值之和以后，如果亮度变化很大，中央像素的亮度会增加（反之则不会）。换句话说，如果一个像素比它周围的像素更突出，就会提升它的亮度。这在边缘检测上尤其有效，它会采用一种称为高频提升滤波器(high boost filter)的高通滤波器。高通和低通滤波器都有一个称为半径(radius)的属性，它决定了多大面积的邻近像素参与滤波计算
import cv2
import numpy as np
from skimage import io
from scipy import ndimage
kernel_3x3 = np.array([[-1, -1, -1],
[-1, 8, -1],
[-1, -1, -1]])
kernel_5x5 = np.array([[-1, -1, -1, -1, -1],
[-1, 1, 2, 1, -1],
[-1, 2, 4, 2, -1],
[-1, 1, 2, 1, -1],
[-1, -1, -1, -1, -1]])
img = io.imread(r"D:\F\eclipse-workspace\imagop\src\1.png",as_grey=True)
k3 = ndimage.convolve(img, kernel_3x3)
k5 = ndimage.convolve(img, kernel_5x5)
blurred = cv2.GaussianBlur(img, (17,17), 0)
g_hpf = img - blurred
cv2.namedWindow('3x3', 0)
cv2.imshow("3x3", k3)
cv2.namedWindow('5x5', 0)
cv2.imshow("5x5", k5)
cv2.namedWindow('g_hpf', 0)
cv2.imshow("g_hpf", g_hpf)
cv2.waitKey(0)
cv2.destroyAllWindows()输出：
描绘边缘并模拟肖像胶卷色彩
cameo.py
import cv2
import filters
from managers import WindowManager, CaptureManager
class Cameo(object):
def __init__(self):
self._windowManager = WindowManager('Cameo',
self.onKeypress)
self._captureManager = CaptureManager(
cv2.VideoCapture(0), self._windowManager, True)
self._curveFilter = filters.BGRPortraCurveFilter()
def run(self):
"""Run the main loop."""
self._windowManager.createWindow()
while self._windowManager.isWindowCreated:
self._captureManager.enterFrame()
frame = self._captureManager.frame
if frame is not None:
# TODO: Track faces (Chapter 3).
filters.strokeEdges(frame, frame)
self._curveFilter.apply(frame, frame)
self._captureManager.exitFrame()
self._windowManager.processEvents()
def onKeypress(self, keycode):
"""Handle a keypress.
space -> Take a screenshot.
tab -> Start/stop recording a screencast.
escape -> Quit.
"""
if keycode == 32: # space
self._captureManager.writeImage('screenshot.png')
elif keycode == 9: # tab
if not self._captureManager.isWritingVideo:
self._captureManager.startWritingVideo(
'screencast.avi')
else:
self._captureManager.stopWritingVideo()
elif keycode == 27: # escape
self._windowManager.destroyWindow()
if __name__=="__main__":
Cameo().run()import cv2
import numpy
import time
class CaptureManager(object):
def __init__(self, capture, previewWindowManager = None,
shouldMirrorPreview = False):
self.previewWindowManager = previewWindowManager
self.shouldMirrorPreview = shouldMirrorPreview
self._capture = capture
self._channel = 0
self._enteredFrame = False
self._frame = None
self._imageFilename = None
self._videoFilename = None
self._videoEncoding = None
self._videoWriter = None
self._startTime = None
self._framesElapsed = int(0)
self._fpsEstimate = None
@property
def channel(self):
return self._channel
@channel.setter
def channel(self, value):
if self._channel != value:
self._channel = value
self._frame = None
@property
def frame(self):
if self._enteredFrame and self._frame is None:
# As of OpenCV 3.0, VideoCapture.retrieve() no longer supports
# the channel argument.
# _, self._frame = self._capture.retrieve(channel = self.channel)
_, self._frame = self._capture.retrieve()
return self._frame
@property
def isWritingImage(self):
return self._imageFilename is not None
@property
def isWritingVideo(self):
return self._videoFilename is not None
def enterFrame(self):
"""Capture the next frame, if any."""
# But first, check that any previous frame was exited.
assert not self._enteredFrame, \
'previous enterFrame() had no matching exitFrame()'
if self._capture is not None:
self._enteredFrame = self._capture.grab()
def exitFrame(self):
"""Draw to the window. Write to files. Release the frame."""
# Check whether any grabbed frame is retrievable.
# The getter may retrieve and cache the frame.
if self.frame is None:
self._enteredFrame = False
return
# Update the FPS estimate and related variables.
if self._framesElapsed == 0:
self._startTime = time.time()
else:
timeElapsed = time.time() - self._startTime
self._fpsEstimate = self._framesElapsed / timeElapsed
self._framesElapsed += 1
# Draw to the window, if any.
if self.previewWindowManager is not None:
if self.shouldMirrorPreview:
mirroredFrame = numpy.fliplr(self._frame).copy()
self.previewWindowManager.show(mirroredFrame)
else:
self.previewWindowManager.show(self._frame)
# Write to the image file, if any.
if self.isWritingImage:
cv2.imwrite(self._imageFilename, self._frame)
self._imageFilename = None
# Write to the video file, if any.
self._writeVideoFrame()
# Release the frame.
self._frame = None
self._enteredFrame = False
def writeImage(self, filename):
"""Write the next exited frame to an image file."""
self._imageFilename = filename
def startWritingVideo(
self, filename,
encoding = cv2.VideoWriter_fourcc('M','J','P','G')):
"""Start writing exited frames to a video file."""
self._videoFilename = filename
self._videoEncoding = encoding
def stopWritingVideo(self):
"""Stop writing exited frames to a video file."""
self._videoFilename = None
self._videoEncoding = None
self._videoWriter = None
def _writeVideoFrame(self):
if not self.isWritingVideo:
return
if self._videoWriter is None:
fps = self._capture.get(cv2.CAP_PROP_FPS)
if fps <= 0.0:
# The capture's FPS is unknown so use an estimate.
if self._framesElapsed < 20:
# Wait until more frames elapse so that the
# estimate is more stable.
return
else:
fps = self._fpsEstimate
size = (int(self._capture.get(
cv2.CAP_PROP_FRAME_WIDTH)),
int(self._capture.get(
cv2.CAP_PROP_FRAME_HEIGHT)))
self._videoWriter = cv2.VideoWriter(
self._videoFilename, self._videoEncoding,
fps, size)
self._videoWriter.write(self._frame)
class WindowManager(object):
def __init__(self, windowName, keypressCallback = None):
self.keypressCallback = keypressCallback
self._windowName = windowName
self._isWindowCreated = False
@property
def isWindowCreated(self):
return self._isWindowCreated
def createWindow(self):
cv2.namedWindow(self._windowName)
self._isWindowCreated = True
def show(self, frame):
cv2.imshow(self._windowName, frame)
def destroyWindow(self):
cv2.destroyWindow(self._windowName)
self._isWindowCreated = False
def processEvents(self):
keycode = cv2.waitKey(1)
if self.keypressCallback is not None and keycode != -1:
# Discard any non-ASCII info encoded by GTK.
keycode &= 0xFF
self.keypressCallback(keycode)截图效果：
