Painting using PYQT - qt

Question

I am trying to implement a program like paint in PYQT. I am trying to use the code of Scribble example in PYQT package which can be found in: C:\Python26\Lib\site-packages\PyQt4\examples\widgets. Now regarding this I have 2 questions:
In the Scribble program, when painting, the paint doesn't get updated visually in real-time as you are holding the mouse button and scribbling. I found out that this problem comes from the function drawLineTo from class ScribbleArea, the line:
self.update(QtCore.QRect(self.lastPoint, endPoint).normalized().adjusted(-rad, -rad, +rad, +rad))
Now if I simply replace this line with
self.update()
the problem is solved, but the cursor is not in the exact location the paintin happens.
Do you know what parameters I can add in the self.update() which solves both problems?
I want to open an image as Scribble does and paint on it and then save only the paint with a blank lets say white background (without the original image in the back ground). Can you tell me how to do this?
I would appreciate your answer to either of the questions.
Thanks!

Answer 1

Just learning pyqt, but I modified the code to take care of the cursor mismatch problem (and modified the openImage method to also keep the image size in sync with the window):
#!/usr/bin/env python
#############################################################################
##
## Copyright (C) 2010 Riverbank Computing Limited.
## Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
## All rights reserved.
##
## This file is part of the examples of PyQt.
##
## $QT_BEGIN_LICENSE:BSD$
## You may use this file under the terms of the BSD license as follows:
##
## "Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are
## met:
## * Redistributions of source code must retain the above copyright
## notice, this list of conditions and the following disclaimer.
## * Redistributions in binary form must reproduce the above copyright
## notice, this list of conditions and the following disclaimer in
## the documentation and/or other materials provided with the
## distribution.
## * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
## the names of its contributors may be used to endorse or promote
## products derived from this software without specific prior written
## permission.
##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
## "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
## LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
## A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
## OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
## SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
## LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
## DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
## THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
## (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
## $QT_END_LICENSE$
##
#############################################################################
# These are only needed for Python v2 but are harmless for Python v3.
import sip
sip.setapi('QString', 2)
sip.setapi('QVariant', 2)
from PyQt4 import QtCore, QtGui
class ScribbleArea(QtGui.QWidget):
"""
this scales the image but it's not good, too many refreshes really mess it up!!!
"""
def __init__(self, parent=None):
super(ScribbleArea, self).__init__(parent)
self.setAttribute(QtCore.Qt.WA_StaticContents)
self.modified = False
self.scribbling = False
self.myPenWidth = 1
self.myPenColor = QtCore.Qt.blue
imageSize = QtCore.QSize(500, 500)
# self.image = QtGui.QImage()
self.image = QtGui.QImage(imageSize, QtGui.QImage.Format_RGB32)
self.lastPoint = QtCore.QPoint()
def openImage(self, fileName):
loadedImage = QtGui.QImage()
if not loadedImage.load(fileName):
return False
w = loadedImage.width()
h = loadedImage.height()
self.mainWindow.resize(w, h)
# newSize = loadedImage.size().expandedTo(self.size())
# self.resizeImage(loadedImage, newSize)
self.image = loadedImage
self.modified = False
self.update()
return True
def saveImage(self, fileName, fileFormat):
visibleImage = self.image
self.resizeImage(visibleImage, self.size())
if visibleImage.save(fileName, fileFormat):
self.modified = False
return True
else:
return False
def setPenColor(self, newColor):
self.myPenColor = newColor
def setPenWidth(self, newWidth):
self.myPenWidth = newWidth
def clearImage(self):
self.image.fill(QtGui.qRgb(255, 255, 255))
self.modified = True
self.update()
def mousePressEvent(self, event):
# print "self.image.width() = %d" % self.image.width()
# print "self.image.height() = %d" % self.image.height()
# print "self.image.size() = %s" % self.image.size()
# print "self.size() = %s" % self.size()
# print "event.pos() = %s" % event.pos()
if event.button() == QtCore.Qt.LeftButton:
self.lastPoint = event.pos()
self.scribbling = True
def mouseMoveEvent(self, event):
if (event.buttons() & QtCore.Qt.LeftButton) and self.scribbling:
self.drawLineTo(event.pos())
def mouseReleaseEvent(self, event):
if event.button() == QtCore.Qt.LeftButton and self.scribbling:
self.drawLineTo(event.pos())
self.scribbling = False
def paintEvent(self, event):
painter = QtGui.QPainter(self)
painter.drawImage(event.rect(), self.image)
def resizeEvent(self, event):
# print "resize event"
# print "event = %s" % event
# print "event.oldSize() = %s" % event.oldSize()
# print "event.size() = %s" % event.size()
self.resizeImage(self.image, event.size())
# if self.width() > self.image.width() or self.height() > self.image.height():
# newWidth = max(self.width() + 128, self.image.width())
# newHeight = max(self.height() + 128, self.image.height())
# print "newWidth = %d, newHeight = %d" % (newWidth, newHeight)
# self.resizeImage(self.image, QtCore.QSize(newWidth, newHeight))
# self.update()
super(ScribbleArea, self).resizeEvent(event)
def drawLineTo(self, endPoint):
painter = QtGui.QPainter(self.image)
painter.setPen(QtGui.QPen(self.myPenColor, self.myPenWidth,
QtCore.Qt.SolidLine, QtCore.Qt.RoundCap, QtCore.Qt.RoundJoin))
painter.drawLine(self.lastPoint, endPoint)
self.modified = True
# rad = self.myPenWidth / 2 + 2
# self.update(QtCore.QRect(self.lastPoint, endPoint).normalized().adjusted(-rad, -rad, +rad, +rad))
self.update()
self.lastPoint = QtCore.QPoint(endPoint)
def resizeImage(self, image, newSize):
if image.size() == newSize:
return
# print "image.size() = %s" % repr(image.size())
# print "newSize = %s" % newSize
# this resizes the canvas without resampling the image
newImage = QtGui.QImage(newSize, QtGui.QImage.Format_RGB32)
newImage.fill(QtGui.qRgb(255, 255, 255))
painter = QtGui.QPainter(newImage)
painter.drawImage(QtCore.QPoint(0, 0), image)
## this resampled the image but it gets messed up with so many events...
## painter.setRenderHint(QtGui.QPainter.SmoothPixmapTransform, True)
## painter.setRenderHint(QtGui.QPainter.HighQualityAntialiasing, True)
#
# newImage = QtGui.QImage(newSize, QtGui.QImage.Format_RGB32)
# newImage.fill(QtGui.qRgb(255, 255, 255))
# painter = QtGui.QPainter(newImage)
# srcRect = QtCore.QRect(QtCore.QPoint(0,0), image.size())
# dstRect = QtCore.QRect(QtCore.QPoint(0,0), newSize)
## print "srcRect = %s" % srcRect
## print "dstRect = %s" % dstRect
# painter.drawImage(dstRect, image, srcRect)
self.image = newImage
def print_(self):
printer = QtGui.QPrinter(QtGui.QPrinter.HighResolution)
printDialog = QtGui.QPrintDialog(printer, self)
if printDialog.exec_() == QtGui.QDialog.Accepted:
painter = QtGui.QPainter(printer)
rect = painter.viewport()
size = self.image.size()
size.scale(rect.size(), QtCore.Qt.KeepAspectRatio)
painter.setViewport(rect.x(), rect.y(), size.width(), size.height())
painter.setWindow(self.image.rect())
painter.drawImage(0, 0, self.image)
painter.end()
def isModified(self):
return self.modified
def penColor(self):
return self.myPenColor
def penWidth(self):
return self.myPenWidth
class MainWindow(QtGui.QMainWindow):
def __init__(self):
super(MainWindow, self).__init__()
self.saveAsActs = []
self.scribbleArea = ScribbleArea(self)
self.scribbleArea.clearImage()
self.scribbleArea.mainWindow = self # maybe not using this?
self.setCentralWidget(self.scribbleArea)
self.createActions()
self.createMenus()
self.setWindowTitle("Scribble")
self.resize(500, 500)
def closeEvent(self, event):
if self.maybeSave():
event.accept()
else:
event.ignore()
def open(self):
if self.maybeSave():
fileName = QtGui.QFileDialog.getOpenFileName(self, "Open File",
QtCore.QDir.currentPath())
if fileName:
self.scribbleArea.openImage(fileName)
def save(self):
action = self.sender()
fileFormat = action.data()
self.saveFile(fileFormat)
def penColor(self):
newColor = QtGui.QColorDialog.getColor(self.scribbleArea.penColor())
if newColor.isValid():
self.scribbleArea.setPenColor(newColor)
def penWidth(self):
newWidth, ok = QtGui.QInputDialog.getInteger(self, "Scribble",
"Select pen width:", self.scribbleArea.penWidth(), 1, 50, 1)
if ok:
self.scribbleArea.setPenWidth(newWidth)
def about(self):
QtGui.QMessageBox.about(self, "About Scribble",
"<p>The <b>Scribble</b> example shows how to use "
"QMainWindow as the base widget for an application, and how "
"to reimplement some of QWidget's event handlers to receive "
"the events generated for the application's widgets:</p>"
"<p> We reimplement the mouse event handlers to facilitate "
"drawing, the paint event handler to update the application "
"and the resize event handler to optimize the application's "
"appearance. In addition we reimplement the close event "
"handler to intercept the close events before terminating "
"the application.</p>"
"<p> The example also demonstrates how to use QPainter to "
"draw an image in real time, as well as to repaint "
"widgets.</p>")
def createActions(self):
self.openAct = QtGui.QAction("&Open...", self, shortcut="Ctrl+O",
triggered=self.open)
for format in QtGui.QImageWriter.supportedImageFormats():
format = str(format)
text = format.upper() + "..."
action = QtGui.QAction(text, self, triggered=self.save)
action.setData(format)
self.saveAsActs.append(action)
self.printAct = QtGui.QAction("&Print...", self,
triggered=self.scribbleArea.print_)
self.exitAct = QtGui.QAction("E&xit", self, shortcut="Ctrl+Q",
triggered=self.close)
self.penColorAct = QtGui.QAction("&Pen Color...", self,
triggered=self.penColor)
self.penWidthAct = QtGui.QAction("Pen &Width...", self,
triggered=self.penWidth)
self.clearScreenAct = QtGui.QAction("&Clear Screen", self,
shortcut="Ctrl+L", triggered=self.scribbleArea.clearImage)
self.aboutAct = QtGui.QAction("&About", self, triggered=self.about)
self.aboutQtAct = QtGui.QAction("About &Qt", self,
triggered=QtGui.qApp.aboutQt)
def createMenus(self):
self.saveAsMenu = QtGui.QMenu("&Save As", self)
for action in self.saveAsActs:
self.saveAsMenu.addAction(action)
fileMenu = QtGui.QMenu("&File", self)
fileMenu.addAction(self.openAct)
fileMenu.addMenu(self.saveAsMenu)
fileMenu.addAction(self.printAct)
fileMenu.addSeparator()
fileMenu.addAction(self.exitAct)
optionMenu = QtGui.QMenu("&Options", self)
optionMenu.addAction(self.penColorAct)
optionMenu.addAction(self.penWidthAct)
optionMenu.addSeparator()
optionMenu.addAction(self.clearScreenAct)
helpMenu = QtGui.QMenu("&Help", self)
helpMenu.addAction(self.aboutAct)
helpMenu.addAction(self.aboutQtAct)
self.menuBar().addMenu(fileMenu)
self.menuBar().addMenu(optionMenu)
self.menuBar().addMenu(helpMenu)
def maybeSave(self):
if self.scribbleArea.isModified():
ret = QtGui.QMessageBox.warning(self, "Scribble",
"The image has been modified.\n"
"Do you want to save your changes?",
QtGui.QMessageBox.Save | QtGui.QMessageBox.Discard |
QtGui.QMessageBox.Cancel)
if ret == QtGui.QMessageBox.Save:
return self.saveFile('png')
elif ret == QtGui.QMessageBox.Cancel:
return False
return True
def saveFile(self, fileFormat):
initialPath = QtCore.QDir.currentPath() + '/untitled.' + fileFormat
fileName = QtGui.QFileDialog.getSaveFileName(self, "Save As",
initialPath,
"%s Files (*.%s);;All Files (*)" % (fileFormat.upper(), fileFormat))
if fileName:
return self.scribbleArea.saveImage(fileName, fileFormat)
return False
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
window = MainWindow()
window.show()
sys.exit(app.exec_())