詳解如何在pyqt中通過OpenCV實現(xiàn)對窗口的透視變換

發(fā)布時間：2020-10-14 14:24:36 來源：腳本之家閱讀：226 作者：之一Yo 欄目：開發(fā)技術

窗口的透視變換效果

當我們點擊Win10的UWP應用中的小部件時，會發(fā)現(xiàn)小部件會朝著鼠標點擊位置凹陷下去，而且不同的點擊位置對應著不同的凹陷情況，看起來就好像小部件在屏幕上不只有x軸和y軸，甚至還有一個z軸。要做到這一點，其實只要對窗口進行透視變換即可。下面是對Qt的窗口和按鈕進行透視變換的效果：

具體代碼

1.下面先定義一個類，它的作用是將傳入的 QPixmap 轉(zhuǎn)換為numpy 數(shù)組，然后用 opencv 的 warpPerspective 對數(shù)組進行透視變換，最后再將 numpy 數(shù)組轉(zhuǎn)為 QPixmap 并返回；

# coding:utf-8

import cv2 as cv
import numpy
from PyQt5.QtGui import QImage, QPixmap


class PixmapPerspectiveTransform:
 """ 透視變換基類 """

 def __init__(self, pixmap=None):
  """ 實例化透視變換對象\n
  Parameter
  ---------
  src : numpy數(shù)組 """
  self.pixmap = pixmap

 def setPixmap(self, pixmap: QPixmap):
  """ 設置被變換的QPixmap """
  self.pixmap = QPixmap
  self.src=self.transQPixmapToNdarray(pixmap)
  self.height, self.width = self.src.shape[:2]
  # 變換前后的邊角坐標
  self.srcPoints = numpy.float32(
   [[0, 0], [self.width - 1, 0], [0, self.height - 1],
    [self.width - 1, self.height - 1]])

 def setDstPoints(self, leftTop: list, rightTop, leftBottom, rightBottom):
  """ 設置變換后的邊角坐標 """
  self.dstPoints = numpy.float32(
   [leftTop, rightTop, leftBottom, rightBottom])

 def getPerspectiveTransform(self, imWidth, imHeight, borderMode=cv.BORDER_CONSTANT, borderValue=[255, 255, 255, 0]) -> QPixmap:
  """ 透視變換圖像，返回QPixmap\n
  Parameters
  ----------
  imWidth : 變換后的圖像寬度\n
  imHeight : 變換后的圖像高度\n
  borderMode : 邊框插值方式\n
  borderValue : 邊框顏色
  """
  # 如果是jpg需要加上一個透明通道
  if self.src.shape[-1] == 3:
   self.src = cv.cvtColor(self.src, cv.COLOR_BGR2BGRA)
  # 透視變換矩陣
  perspectiveMatrix = cv.getPerspectiveTransform(
   self.srcPoints, self.dstPoints)
  # 執(zhí)行變換
  self.dst = cv.warpPerspective(self.src, perspectiveMatrix, (
   imWidth, imHeight), borderMode=borderMode, borderValue=borderValue)
  # 將ndarray轉(zhuǎn)換為QPixmap
  return self.transNdarrayToQPixmap(self.dst)

 def transQPixmapToNdarray(self, pixmap: QPixmap):
  """ 將QPixmap轉(zhuǎn)換為numpy數(shù)組 """
  width, height = pixmap.width(), pixmap.height()
  channels_count = 4
  image = pixmap.toImage() # type:QImage
  s = image.bits().asstring(height * width * channels_count)
  # 得到BGRA格式數(shù)組
  array = numpy.fromstring(s, numpy.uint8).reshape(
   (height, width, channels_count))
  return array

 def transNdarrayToQPixmap(self, array):
  """ 將numpy數(shù)組轉(zhuǎn)換為QPixmap """
  height, width, bytesPerComponent = array.shape
  bytesPerLine = 4 * width
  # 默認數(shù)組維度為 m*n*4
  dst = cv.cvtColor(array, cv.COLOR_BGRA2RGBA)
  pix = QPixmap.fromImage(
   QImage(dst.data, width, height, bytesPerLine, QImage.Format_RGBA8888))
  return pix

2.接下來就是這篇博客的主角——PerspectiveWidget，當我們的鼠標單擊這個類實例化出來的窗口時，窗口會先通過 self.grab() 被渲染為QPixmap，然后調(diào)用 PixmapPerspectiveTransform 中的方法對QPixmap進行透視變換，拿到透視變換的結(jié)果后只需隱藏窗口內(nèi)的小部件并通過 PaintEvent 將結(jié)果繪制到窗口上即可。雖然思路很通順，但是實際操作起來會發(fā)現(xiàn)對于透明背景的窗口進行透視變換時，與透明部分交界的部分會被插值上半透明的像素。對于本來就屬于深色的像素來說這沒什么，但是如果像素是淺色的就會帶來很大的視覺干擾，你會發(fā)現(xiàn)這些淺色部分旁邊被描上了一圈黑邊，我們先將這個圖像記為img_1。img_1差不多長這個樣子，可以很明顯看出白色的文字圍繞著一圈黑色的描邊。

詳解如何在pyqt中通過OpenCV實現(xiàn)對窗口的透視變換

為了解決這個煩人的問題，我又對桌面上的窗口進行截屏，再次透視變換。注意是桌面上看到的窗口，這時的窗口肯定是會有背景的，這時的透視變換就不會存在上述問題，記這個透視變換完的圖像為img_2。但實際上我們本來是不想要img_2中的背景的，所以只要將img_2中的背景替換完img_1中的透明背景，下面是具體代碼：

# coding:utf-8

import numpy as np

from PyQt5.QtCore import QPoint, Qt
from PyQt5.QtGui import QPainter, QPixmap, QScreen, QImage
from PyQt5.QtWidgets import QApplication, QWidget

from my_functions.get_pressed_pos import getPressedPos
from my_functions.perspective_transform_cv import PixmapPerspectiveTransform


class PerspectiveWidget(QWidget):
 """ 可進行透視變換的窗口 """

 def __init__(self, parent=None, isTransScreenshot=False):
  super().__init__(parent)
  self.__visibleChildren = []
  self.__isTransScreenshot = isTransScreenshot
  self.__perspectiveTrans = PixmapPerspectiveTransform() 
  self.__screenshotPix = None
  self.__pressedPix = None
  self.__pressedPos = None

 @property
 def pressedPos(self) -> str:
  """ 返回鼠標點擊位置 """
  return self.__pressedPos

 def mousePressEvent(self, e):
  """ 鼠標點擊窗口時進行透視變換 """
  super().mousePressEvent(e)
  self.grabMouse()
  pixmap = self.grab()
  self.__perspectiveTrans.setPixmap(pixmap)
  # 根據(jù)鼠標點擊位置的不同設置背景封面的透視變換
  self.__setDstPointsByPressedPos(getPressedPos(self,e))
  # 獲取透視變換后的QPixmap
  self.__pressedPix = self.__getTransformPixmap()
  # 對桌面上的窗口進行截圖
  if self.__isTransScreenshot:
   self.__adjustTransformPix()
  # 隱藏本來看得見的小部件
  self.__visibleChildren = [
   child for child in self.children() if hasattr(child, 'isVisible') and child.isVisible()]
  for child in self.__visibleChildren:
   if hasattr(child, 'hide'):
    child.hide()
  self.update()

 def mouseReleaseEvent(self, e):
  """ 鼠標松開時顯示小部件 """
  super().mouseReleaseEvent(e)
  self.releaseMouse()
  self.__pressedPos = None
  self.update()
  # 顯示小部件
  for child in self.__visibleChildren:
   if hasattr(child, 'show'):
    child.show()

 def paintEvent(self, e):
  """ 繪制背景 """
  super().paintEvent(e)
  painter = QPainter(self)
  painter.setRenderHints(QPainter.Antialiasing | QPainter.HighQualityAntialiasing |
        QPainter.SmoothPixmapTransform)
  painter.setPen(Qt.NoPen)
  # 繪制背景圖片
  if self.__pressedPos:
   painter.drawPixmap(self.rect(), self.__pressedPix)

 def __setDstPointsByPressedPos(self,pressedPos:str):
  """ 通過鼠標點擊位置設置透視變換的四個邊角坐標 """
  self.__pressedPos = pressedPos
  if self.__pressedPos == 'left':
   self.__perspectiveTrans.setDstPoints(
    [5, 4], [self.__perspectiveTrans.width - 2, 1],
    [3, self.__perspectiveTrans.height - 3],
    [self.__perspectiveTrans.width - 2, self.__perspectiveTrans.height - 1])
  elif self.__pressedPos == 'left-top':
   self.__perspectiveTrans.setDstPoints(
    [6, 5], [self.__perspectiveTrans.width - 1, 1],
    [1, self.__perspectiveTrans.height - 2],
    [self.__perspectiveTrans.width - 2, self.__perspectiveTrans.height - 1])
  elif self.__pressedPos == 'left-bottom':
   self.__perspectiveTrans.setDstPoints(
    [2, 3], [self.__perspectiveTrans.width - 3, 0],
    [4, self.__perspectiveTrans.height - 4],
    [self.__perspectiveTrans.width - 2, self.__perspectiveTrans.height - 2])
  elif self.__pressedPos == 'top':
   self.__perspectiveTrans.setDstPoints(
    [3, 5], [self.__perspectiveTrans.width - 4, 5],
    [1, self.__perspectiveTrans.height - 2],
    [self.__perspectiveTrans.width - 2, self.__perspectiveTrans.height - 2])
  elif self.__pressedPos == 'center':
   self.__perspectiveTrans.setDstPoints(
    [3, 4], [self.__perspectiveTrans.width - 4, 4],
    [3, self.__perspectiveTrans.height - 3],
    [self.__perspectiveTrans.width - 4, self.__perspectiveTrans.height - 3])
  elif self.__pressedPos == 'bottom':
   self.__perspectiveTrans.setDstPoints(
    [2, 2], [self.__perspectiveTrans.width - 3, 3],
    [3, self.__perspectiveTrans.height - 3],
    [self.__perspectiveTrans.width - 4, self.__perspectiveTrans.height - 3])
  elif self.__pressedPos == 'right-bottom':
   self.__perspectiveTrans.setDstPoints(
    [1, 0], [self.__perspectiveTrans.width - 3, 2],
    [1, self.__perspectiveTrans.height - 2],
    [self.__perspectiveTrans.width - 5, self.__perspectiveTrans.height - 4])
  elif self.__pressedPos == 'right-top':
   self.__perspectiveTrans.setDstPoints(
    [0, 1], [self.__perspectiveTrans.width - 7, 5],
    [2, self.__perspectiveTrans.height - 1],
    [self.__perspectiveTrans.width - 2, self.__perspectiveTrans.height - 2])
  elif self.__pressedPos == 'right':
   self.__perspectiveTrans.setDstPoints(
    [1, 1], [self.__perspectiveTrans.width - 6, 4],
    [2, self.__perspectiveTrans.height - 1],
    [self.__perspectiveTrans.width - 4, self.__perspectiveTrans.height - 3])

 def __getTransformPixmap(self) -> QPixmap:
  """ 獲取透視變換后的QPixmap """
  pix = self.__perspectiveTrans.getPerspectiveTransform(
   self.__perspectiveTrans.width, self.__perspectiveTrans.height).scaled(
    self.size(), Qt.KeepAspectRatio, Qt.SmoothTransformation)
  return pix

 def __getScreenShot(self) -> QPixmap:
  """ 對窗口口所在的桌面區(qū)域進行截圖 """
  screen = QApplication.primaryScreen() # type:QScreen
  pos = self.mapToGlobal(QPoint(0, 0)) # type:QPoint
  pix = screen.grabWindow(
   0, pos.x(), pos.y(), self.width(), self.height())
  return pix

 def __adjustTransformPix(self):
  """ 對窗口截圖再次進行透視變換并將兩張圖融合，消除可能存在的黑邊 """
  self.__screenshotPix = self.__getScreenShot()
  self.__perspectiveTrans.setPixmap(self.__screenshotPix)
  self.__screenshotPressedPix = self.__getTransformPixmap()
  # 融合兩張透視圖
  img_1 = self.__perspectiveTrans.transQPixmapToNdarray(self.__pressedPix)
  img_2 = self.__perspectiveTrans.transQPixmapToNdarray(self.__screenshotPressedPix)
  # 去除非透明背景部分  
  mask = img_1[:, :, -1] == 0
  img_2[mask] = img_1[mask]
  self.__pressedPix = self.__perspectiveTrans.transNdarrayToQPixmap(img_2)

在mousePressEvent中調(diào)用了一個全局函數(shù) getPressedPos(widget,e) ，如果將窗口分為九宮格，它就是用來獲取判斷鼠標的點擊位置落在九宮格的哪個格子的，因為我在其他地方有用到它，所以沒將其設置為PerspectiveWidget的方法成員。下面是這個函數(shù)的代碼：

# coding:utf-8

from PyQt5.QtGui import QMouseEvent


def getPressedPos(widget, e: QMouseEvent) -> str:
 """ 檢測鼠標并返回按下的方位 """
 pressedPos = None
 width = widget.width()
 height = widget.height()
 leftX = 0 <= e.x() <= int(width / 3)
 midX = int(width / 3) < e.x() <= int(width * 2 / 3)
 rightX = int(width * 2 / 3) < e.x() <= width
 topY = 0 <= e.y() <= int(height / 3)
 midY = int(height / 3) < e.y() <= int(height * 2 / 3)
 bottomY = int(height * 2 / 3) < e.y() <= height
 # 獲取點擊位置
 if leftX and topY:
  pressedPos = 'left-top'
 elif midX and topY:
  pressedPos = 'top'
 elif rightX and topY:
  pressedPos = 'right-top'
 elif leftX and midY:
  pressedPos = 'left'
 elif midX and midY:
  pressedPos = 'center'
 elif rightX and midY:
  pressedPos = 'right'
 elif leftX and bottomY:
  pressedPos = 'left-bottom'
 elif midX and bottomY:
  pressedPos = 'bottom'
 elif rightX and bottomY:
  pressedPos = 'right-bottom'
 return pressedPos

使用方法

很簡單，只要將代碼中的QWidget替換為PerspectiveWidget就可以享受透視變換帶來的無盡樂趣。要想向gif中那樣對按鈕也進行透視變換，只要按代碼中所做的那樣重寫mousePressEvent、mouseReleaseEvent 和 paintEvent 即可，如果有對按鈕使用qss，記得在paintEvent中加上super().paintEvent(e)，這樣樣式表才會起作用?？傊蚣芤呀?jīng)給出，具體操作取決于你。如果你喜歡這篇博客的話，記得點個贊哦(oﾟ▽ﾟ)o 。順便做個下期預告：在gif中可以看到界面切換時帶了彈入彈出的動畫，在下一篇博客中我會對如何實現(xiàn)QStackedWidget的界面切換動畫進行介紹，敬請期待~~

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