Dane Springmeyer wrote:
Hey, zsj, nice job on this little app!
I tried it out and it works nicely.
I like the smooth zoom - do you think you could get it to match
http://www.khtml.org/osm/v0.59/index.php whereby the zoom centers upon the
current mouse position both when zooming in and out?
After struggling with the 0.71 api doc and finding out what coordinate
transform mapnik uses, I finally modified the widget to scale upon the
current mouse cursor position.
Talking about the smooth scale/drag, if the mapnik rendering procedure
can be terminated safely, the programm will be more responsive upon
complex file. Will it?
Also, I just realized that there may be a few unanswered questions of your
still on the list - could you resend to me?
Yes, I'll send to the list and you soon. There will be some correction
about the questions.
-- Regards, zsj
# -*- coding: utf-8 -*-
import mapnik
from PyQt4.QtCore import *
from PyQt4.QtGui import *
class MapnikWidget(QWidget):
def __init__(self, parent = None):
QWidget.__init__(self, parent)
self.map = mapnik.Map(256, 256)
self.qim = QImage()
self.startDragPos = QPoint()
self.endDragPos = QPoint()
self.zoomPos = QPoint()
self.drag = False
self.scale = False
self.total_scale = 1.0
self.timer = QTimer()
self.timer.timeout.connect(self.updateMap)
def open(self, xml):
mapnik.load_map(self.map, xml)
self.map.resize(self.width(), self.height())
self.zoom_all()
def close_map(self):
self.map = mapnik.Map(256, 256)
self.updateMap()
def updateMap(self):
self.timer.stop()
if self.drag:
cx = int(0.5 * self.map.width)
cy = int(0.5 * self.map.height)
dpos = self.endDragPos - self.startDragPos
self.map.pan(cx - dpos.x() ,cy - dpos.y())
self.drag = False
elif self.scale:
# scale upon the mouse cursor position
# build up the transformation matrix
ma = QMatrix()
# firstly, translate the cursor position to the origin
ma.translate(self.zoomPos.x(), self.zoomPos.y())
# then, do the normal scale upon origin
ma.scale(self.total_scale, self.total_scale)
# finnaly, translate back to the cursor position
ma.translate(-self.zoomPos.x(), -self.zoomPos.y())
rect = ma.mapRect(QRectF(0, 0, self.map.width, self.map.height))
env = mapnik.Envelope(rect.left(), rect.bottom(), rect.right(),
rect.top())
self.map.zoom_to_box(self.map.view_transform().backward(env))
self.total_scale = 1.0
self.scale = False
im = mapnik.Image(self.map.width, self.map.height)
mapnik.render(self.map, im)
self.qim.loadFromData(QByteArray(im.tostring('png')))
self.update()
def paintEvent(self, event):
painter = QPainter(self)
if self.drag:
painter.drawImage(self.endDragPos - self.startDragPos, self.qim)
elif self.scale:
painter.save()
scale = 1 / self.total_scale
painter.translate(self.zoomPos.x(), self.zoomPos.y())
painter.scale(scale, scale)
painter.translate(-self.zoomPos.x(), -self.zoomPos.y())
exposed =
painter.matrix().inverted()[0].mapRect(self.rect()).adjusted(-1, -1, 1, 1)
painter.drawImage(exposed, self.qim, exposed)
painter.restore()
else:
painter.drawImage(0, 0, self.qim)
painter.setPen(QColor(0, 0, 0, 100))
painter.setBrush(QColor(0, 0, 0, 100))
painter.drawRect(0, 0, 256, 26)
painter.setPen(QColor(0, 255 , 0))
painter.drawText(10, 19, 'Scale Denominator: ' +
str(self.map.scale_denominator()))
def zoom_all(self):
self.map.zoom_all()
self.updateMap()
def resizeEvent(self, event):
self.map.resize(event.size().width(), event.size().height())
self.updateMap()
def wheelEvent(self, event):
self.zoomPos = event.pos()
self.total_scale *= 1.0 - event.delta() / (360.0 * 8.0) * 4
self.scale = True
self.update()
self.timer.start(400)
def mousePressEvent(self, event):
if event.button() == Qt.LeftButton:
self.startDragPos = event.pos()
self.drag = True
def mouseMoveEvent(self, event):
if self.drag:
self.endDragPos = event.pos()
self.update()
def mouseReleaseEvent(self, event):
if event.button() == Qt.LeftButton:
self.endDragPos = event.pos()
self.updateMap()
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