【发布时间】：2020-12-13 12:24:59
【问题描述】：
我正在尝试编写一个简单的图像编辑器，例如paint。
我实现了画线矩形和椭圆。
我想要的是看到矩形的样子的动画（铺垫？），就像在绘画中绘制形状时一样，无需真正在画布上绘制就可以看到它的实际外观。
这是代码的简化版本
class Canvas(QWidget):
def __init__(self):
super().__init__()
self.initUI()
self.initLogic()
def initUI(self):
self.image = QImage(self.size(), QImage.Format_RGB32)
self.image.fill(Qt.white)
def initLogic(self):
self.brushSize = 1
self.brushStyle = Qt.SolidLine
self.brushColor = QColor(0, 0, 0)
self.shapeMode = None
self.drawing = False
self.mousePointer = None
def mousePressEvent(self, event):
self.drawing = True
self.mousePointer = event.pos()
def mouseMoveEvent(self, event):
#if no pen mode set draw lines from event to event
if self.drawing:
painter = QPainter(self.image)
painter.setPen(QPen(self.brushColor,
self.brushSize,
self.brushStyle))
shape = None #i try later to assign the method Qpainter.draw<someShape> to this variable
# hoping it works like in tkinter.
if self.shapeMode == None:#free shape
painter.drawLine(self.mousePointer, event.pos())
self.mousePointer = event.pos()
else:
#previous x and previous y
ox, oy = self.mousePointer.x(), self.mousePointer.y()
#current x and current y
dx, dy = event.pos().x(), event.pos().y()
width, height = dx - ox, dy - oy
#self.shapeMode is a string corresponding to a QPainter method
#we get the corresponding method using getattr builtin function
drawMethod = getattr(painter, self.shapeMode)# = painter.someFunc this works fine
shape = drawMethod(ox, oy, width, height) #assigning the method call to a variable
self.update()
if shape != None:
painter.eraseRect(shape)
"""
if self.drawing and self.shapeMode == None:
painter = QPainter(self.image)
painter.setPen(QPen(self.brushColor,
self.brushSize,
self.brushStyle))
painter.drawLine(self.mousePointer, event.pos())
self.mousePointer = event.pos()
self.update()"""
#otherwise if pen mode set draw shape at event then delete until release
def mouseReleaseEvent(self, event):
if self.shapeMode != None:
painter = QPainter(self.image)
painter.setPen(QPen(self.brushColor,
self.brushSize,
self.brushStyle))
#previous x and previous y
ox, oy = self.mousePointer.x(), self.mousePointer.y()
#current x and current y
dx, dy = event.pos().x(), event.pos().y()
width, height = dx - ox, dy - oy
#self.shapeMode is a string corresponding to a QPainter methid
#we get the corresponding method using getattr builtin function
drawMethod = getattr(painter, self.shapeMode)# = painter.someFunc
shape = drawMethod(ox, oy, width, height)
self.update()
self.mousePointer = event.pos()
self.drawing = False
#TODO end registering the action
def paintEvent(self, event):
widgetPainter = QPainter(self)
widgetPainter.drawImage(self.rect(), self.image, self.rect())
只要我按住鼠标，画布就会一直绘制矩形，我想要的是调整大小的矩形，并且只有在鼠标释放后才能最终绘制。
【问题讨论】：