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在我的程序中，我試圖將mousepress的座標映射回圖像的座標尺寸。我在Python中使用PyQt4。下面的程序演示了這個問題。我有一個小部件可以進行一些圖像轉換。在這些圖像轉換之後，圖像顯示在小部件的中心，同時保持圖像的原始高寬比。由於圖像被縮放和平移，因此必須將MouseEvent的座標重新映射到圖像的座標系。PyQt將鼠標按鈕的座標映射到圖像的座標系
下面的程序有一個類「ScalingWidget」，它應該能夠做這些轉換，並且還應該能夠將mouseReleaseEvent中的座標重新映射回圖像的座標系。當我在Layout和mainwindow外部顯示這個小部件時，這個功能完全可以正常工作，但是當我將這個小部件嵌入到一個更大的GUI中時，它會變得很糟糕。然後將它們映射回圖像座標後的座標突然顯示偏移量。
下面的最小程序可以在啓動程序時通過指定標誌-b來啓動，不管是否有bug。選項-n可以將ScalingWidget的實例深入深入到「gui」中，並且嵌入到佈局中的深度越深，可見的bug越強。 愚蠢的是，儘管繪圖表明轉換是正確的，但映射的座標（打印在窗口標題和控制檯中）表示在存在-b標誌時，將它們重新映射回圖像座標會被搞亂。
所以我的問題是：當我的ScalingWidget嵌入到佈局中時，我在做重新映射鼠標座標回圖像尺寸時出錯？
我不認爲重新映射像素是完美的，但是與最終用戶可以定位鼠標一樣準確。有兩個點x = 20，y = 20，在x = 380和y = 380這些可以用作參考點。
任何幫助是最受歡迎的！
#!/usr/bin/env python
from PyQt4 import QtGui
from PyQt4 import QtCore
import sys
import argparse
class ScalingWidget (QtGui.QWidget):
''' Displays a pixmap optimally in the center of the widget, in such way
the pixmap is shown in the middle
'''
white = QtGui.QColor(255,255,255)
black = QtGui.QColor( 0, 0, 0)
arcrect = QtCore.QRect(-10, -10, 20, 20)
def __init__(self):
super(ScalingWidget, self).__init__()
self.pixmap = QtGui.QPixmap(400, 400)
painter = QtGui.QPainter(self.pixmap)
painter.fillRect(self.pixmap.rect(), self.white)
self.point1 = QtCore.QPoint(20, 20)
self.point2 = QtCore.QPoint(380, 380)
painter.setPen(self.black)
painter.drawRect(QtCore.QRect(self.point1, self.point2))
painter.end()
self.matrix = None
def sizeHint(self):
return QtCore.QSize(500,400)
##
# Applies the default transformations
#
def _default_img_transform(self, painter):
#size of widget
winheight = float(self.height())
winwidth = float(self.width())
#size of pixmap
scrwidth = float(self.pixmap.width())
scrheight = float(self.pixmap.height())
assert(painter.transform().isIdentity())
if scrheight <= 0 or scrwidth <= 0:
raise RuntimeError(repr(self) + "Unable to determine Screensize")
widthr = winwidth/scrwidth
heightr = winheight/scrheight
if widthr > heightr:
translate = (winwidth - heightr * scrwidth) /2
painter.translate(translate, 0)
painter.scale(heightr, heightr)
else:
translate = (winheight - widthr * scrheight)/2
painter.translate(0, translate)
painter.scale(widthr, widthr)
# now store the matrix used to map the mouse coordinates back to the
# coordinates of the pixmap
self.matrix = painter.deviceTransform()
def paintEvent(self, e):
painter = QtGui.QPainter(self)
painter.setClipRegion(e.region())
# fill the background of the entire widget.
painter.fillRect(self.rect(), QtGui.QColor(0,0,0))
# transform to place the image nicely in the center of the widget.
self._default_img_transform(painter)
painter.drawPixmap(self.pixmap.rect(), self.pixmap, self.pixmap.rect())
pen = QtGui.QPen(QtGui.QColor(255,0,0))
# Just draw on the points used to make the black rectangle of the pix map
# drawing is not affected, be remapping those coordinates with the "same"
# matrix is.
pen.setWidth(4)
painter.setPen(pen)
painter.save()
painter.translate(self.point1)
painter.drawPoint(0,0)
painter.restore()
painter.save()
painter.translate(self.point2)
painter.drawPoint(0,0)
painter.restore()
painter.end()
def mouseReleaseEvent(self, event):
x, y = float(event.x()), float(event.y())
inverted, invsucces = self.matrix.inverted()
assert(invsucces)
xmapped, ymapped = inverted.map(x,y)
print x, y
print xmapped, ymapped
self.setWindowTitle("mouse x,y = {}, {}, mapped x, y = {},{} "
.format(x, y, xmapped, ymapped)
)
def start_bug():
''' Displays the mouse press mapping bug.
This is a bit contrived, but in the real world
a widget is embedded in deeper in a gui
than a single widget, besides the problem
grows with the depth of embedding.
'''
app = QtGui.QApplication(sys.argv)
win = QtGui.QWidget()
layout = QtGui.QVBoxLayout()
win.setLayout(layout)
widget = None
for i in range(0, args.increase_bug):
if i < args.increase_bug-1:
widget = QtGui.QWidget()
layout.addWidget(widget)
layout= QtGui.QVBoxLayout()
widget.setLayout(layout)
else:
layout.addWidget(ScalingWidget())
win.show()
sys.exit(app.exec_())
def start_no_bug():
''' Does not show the mapping bug, the mouse event.x() and .y() map nicely back to
the coordinate system of the pixmap
'''
app = QtGui.QApplication(sys.argv)
win = ScalingWidget()
win.show()
sys.exit(app.exec_())
# parsing arguments
parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter)
parser.add_argument('-b', '--display-bug', action='store_true',
help="Toggle this option to get the bugged version"
)
parser.add_argument('-n', '--increase-bug', type=int, default=1,
help="Increase the bug by n times."
)
if __name__ == "__main__":
args = parser.parse_args()
if args.display_bug:
start_bug()
else:
start_no_bug()