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详解如何在pyqt中通过OpenCV实现对窗口的透视变换

程序员文章站 2022-06-25 11:55:36
窗口的透视变换效果   当我们点击win10的uwp应用中的小部件时,会发现小部件会朝着鼠标点击位置凹陷下去,而且不同的点击位置对应着不同的凹陷情况,看起来就好像小部件在屏幕上...

窗口的透视变换效果

   当我们点击win10的uwp应用中的小部件时,会发现小部件会朝着鼠标点击位置凹陷下去,而且不同的点击位置对应着不同的凹陷情况,看起来就好像小部件在屏幕上不只有x轴和y轴,甚至还有一个z轴。要做到这一点,其实只要对窗口进行透视变换即可。下面是对qt的窗口和按钮进行透视变换的效果:

详解如何在pyqt中通过OpenCV实现对窗口的透视变换

具体代码

   1.下面先定义一个类,它的作用是将传入的 qpixmap 转换为numpy 数组,然后用 opencvwarpperspective 对数组进行透视变换,最后再将 numpy 数组转为 qpixmap 并返回;

# coding:utf-8

import cv2 as cv
import numpy
from pyqt5.qtgui import qimage, qpixmap


class pixmapperspectivetransform:
 """ 透视变换基类 """

 def __init__(self, pixmap=none):
  """ 实例化透视变换对象\n
  parameter
  ---------
  src : numpy数组 """
  self.pixmap = pixmap

 def setpixmap(self, pixmap: qpixmap):
  """ 设置被变换的qpixmap """
  self.pixmap = qpixmap
  self.src=self.transqpixmaptondarray(pixmap)
  self.height, self.width = self.src.shape[:2]
  # 变换前后的边角坐标
  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):
  """ 设置变换后的边角坐标 """
  self.dstpoints = numpy.float32(
   [lefttop, righttop, leftbottom, rightbottom])

 def getperspectivetransform(self, imwidth, imheight, bordermode=cv.border_constant, bordervalue=[255, 255, 255, 0]) -> qpixmap:
  """ 透视变换图像,返回qpixmap\n
  parameters
  ----------
  imwidth : 变换后的图像宽度\n
  imheight : 变换后的图像高度\n
  bordermode : 边框插值方式\n
  bordervalue : 边框颜色
  """
  # 如果是jpg需要加上一个透明通道
  if self.src.shape[-1] == 3:
   self.src = cv.cvtcolor(self.src, cv.color_bgr2bgra)
  # 透视变换矩阵
  perspectivematrix = cv.getperspectivetransform(
   self.srcpoints, self.dstpoints)
  # 执行变换
  self.dst = cv.warpperspective(self.src, perspectivematrix, (
   imwidth, imheight), bordermode=bordermode, bordervalue=bordervalue)
  # 将ndarray转换为qpixmap
  return self.transndarraytoqpixmap(self.dst)

 def transqpixmaptondarray(self, pixmap: qpixmap):
  """ 将qpixmap转换为numpy数组 """
  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格式数组
  array = numpy.fromstring(s, numpy.uint8).reshape(
   (height, width, channels_count))
  return array

 def transndarraytoqpixmap(self, array):
  """ 将numpy数组转换为qpixmap """
  height, width, bytespercomponent = array.shape
  bytesperline = 4 * width
  # 默认数组维度为 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.接下来就是这篇博客的主角——perspectivewidget,当我们的鼠标单击这个类实例化出来的窗口时,窗口会先通过 self.grab() 被渲染为qpixmap,然后调用 pixmapperspectivetransform 中的方法对qpixmap进行透视变换,拿到透视变换的结果后只需隐藏窗口内的小部件并通过 paintevent 将结果绘制到窗口上即可。虽然思路很通顺,但是实际操作起来会发现对于透明背景的窗口进行透视变换时,与透明部分交界的部分会被插值上半透明的像素。对于本来就属于深色的像素来说这没什么,但是如果像素是浅色的就会带来很大的视觉干扰,你会发现这些浅色部分旁边被描上了一圈黑边,我们先将这个图像记为img_1。img_1差不多长这个样子,可以很明显看出白色的文字围绕着一圈黑色的描边。

详解如何在pyqt中通过OpenCV实现对窗口的透视变换

为了解决这个烦人的问题,我又对桌面上的窗口进行截屏,再次透视变换。注意是桌面上看到的窗口,这时的窗口肯定是会有背景的,这时的透视变换就不会存在上述问题,记这个透视变换完的图像为img_2。但实际上我们本来是不想要img_2中的背景的,所以只要将img_2中的背景替换完img_1中的透明背景,下面是具体代码:

# 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):
 """ 可进行透视变换的窗口 """

 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:
  """ 返回鼠标点击位置 """
  return self.__pressedpos

 def mousepressevent(self, e):
  """ 鼠标点击窗口时进行透视变换 """
  super().mousepressevent(e)
  self.grabmouse()
  pixmap = self.grab()
  self.__perspectivetrans.setpixmap(pixmap)
  # 根据鼠标点击位置的不同设置背景封面的透视变换
  self.__setdstpointsbypressedpos(getpressedpos(self,e))
  # 获取透视变换后的qpixmap
  self.__pressedpix = self.__gettransformpixmap()
  # 对桌面上的窗口进行截图
  if self.__istransscreenshot:
   self.__adjusttransformpix()
  # 隐藏本来看得见的小部件
  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):
  """ 鼠标松开时显示小部件 """
  super().mousereleaseevent(e)
  self.releasemouse()
  self.__pressedpos = none
  self.update()
  # 显示小部件
  for child in self.__visiblechildren:
   if hasattr(child, 'show'):
    child.show()

 def paintevent(self, e):
  """ 绘制背景 """
  super().paintevent(e)
  painter = qpainter(self)
  painter.setrenderhints(qpainter.antialiasing | qpainter.highqualityantialiasing |
        qpainter.smoothpixmaptransform)
  painter.setpen(qt.nopen)
  # 绘制背景图片
  if self.__pressedpos:
   painter.drawpixmap(self.rect(), self.__pressedpix)

 def __setdstpointsbypressedpos(self,pressedpos:str):
  """ 通过鼠标点击位置设置透视变换的四个边角坐标 """
  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:
  """ 获取透视变换后的qpixmap """
  pix = self.__perspectivetrans.getperspectivetransform(
   self.__perspectivetrans.width, self.__perspectivetrans.height).scaled(
    self.size(), qt.keepaspectratio, qt.smoothtransformation)
  return pix

 def __getscreenshot(self) -> qpixmap:
  """ 对窗口口所在的桌面区域进行截图 """
  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):
  """ 对窗口截图再次进行透视变换并将两张图融合,消除可能存在的黑边 """
  self.__screenshotpix = self.__getscreenshot()
  self.__perspectivetrans.setpixmap(self.__screenshotpix)
  self.__screenshotpressedpix = self.__gettransformpixmap()
  # 融合两张透视图
  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)

mousepressevent中调用了一个全局函数 getpressedpos(widget,e) ,如果将窗口分为九宫格,它就是用来获取判断鼠标的点击位置落在九宫格的哪个格子的,因为我在其他地方有用到它,所以没将其设置为perspectivewidget的方法成员。下面是这个函数的代码:

# coding:utf-8

from pyqt5.qtgui import qmouseevent


def getpressedpos(widget, e: qmouseevent) -> str:
 """ 检测鼠标并返回按下的方位 """
 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
 # 获取点击位置
 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

   很简单,只要将代码中的qwidget替换为perspectivewidget就可以享受透视变换带来的无尽乐趣。要想向gif中那样对按钮也进行透视变换,只要按代码中所做的那样重写mousepresseventmousereleaseeventpaintevent 即可,如果有对按钮使用qss,记得在paintevent中加上super().paintevent(e),这样样式表才会起作用。总之框架已经给出,具体操作取决于你。如果你喜欢这篇博客的话,记得点个赞哦(o゚▽゚)o 。顺便做个下期预告:在gif中可以看到界面切换时带了弹入弹出的动画,在下一篇博客中我会对如何实现qstackedwidget的界面切换动画进行介绍,敬请期待~~

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