qpainter

问题 I'm trying to draw a 3-pixel large point with QPainter . But the following code instead draws a horizontal line with width of 3 pixels. #include <QPainter> #include <QImage> int main() { const int w=1000, h=1000; QImage img(w, h, QImage::Format_RGBX8888); { QPainter p(&img); p.fillRect(0,0,w,h,Qt::black); p.scale(w,h); p.setPen(QPen(Qt::red, 3./w, Qt::SolidLine, Qt::RoundCap)); p.drawPoint(QPointF(0.1,0.1)); } img.save("test.png"); } Here's the top left corner of the resulting image: I am

问题 By default QPainter has its origin point in top-left corner. I want to draw shapes but all coordinates that I have are in cartesian system. So my question - how can I change the origin point to bottom-left corner? Sure, I can scale(1,-1) but then drawText() also scaled and prints inverted text. All I nee it just move origin point. 回答1: QPainter painter(this); painter.translate(this.rect().bottomLeft()); painter.scale(1.0, -1.0); 回答2: You can use void QPainter::translate ( const QPointF &

问题 I'm working on simple 2D visualization module for MD simulation code. What I'm trying to do is drawing positions of simulated molecules using: myPainter.drawEllipse(myQPoint,myRx,myRy) And that part works pretty good on my visualization widget. The thing that happened to be a problem is writing text which should represent each molecule's ID (integer). myPainter.drawText(myPosPoint,QString::number(mySoftMolecule2D->getID())); It draws text but it is too large. This is probably because I need

问题 I have to create an Icon pixmap, two methods I am familiarized to do that, One is setting the pixmap as o QLabel and display it, and other is drawing pixmap using QPainter , ie Method one Icon::Icon { QLabel iconLab = new QLabel; QLabel iconName = new QLabel; iconLab->setPixmap("mypixmap.png"); iconName->setText("myiconname"); QVBoxLayout *iconLayout = new QVBoxLayout; iconLayout->setMargin(0); iconLayout->addWidget(iconLab, 1, Qt::AlignCenter); iconLayout->addWidget(iconName, 1, Qt:

问题 In my application , have a QTextEdit dialog that accepts Rich Text Input. I need to convert this input in to an image for some purpose . If it was Plain text i could use DrawText associated with the QPainter class . But Rich text cannot be dealt the same way as we don't know the formatting done. Any suggestions on how to convert ? 回答1: You may use QTextEdit::document + QTextDocument::drawContents. You don't need any hacks with rendering widgets, as proposed by other authors, because there may

问题 I have QPainterPath. I need to find y coordinate of QPainterPath by x. I found intersected() method in QPainterPath. So, I created new QPainterPath, which is line from left to right edge of my path's bounding rect with x coordinate, to find point as result of intersection. intersects() method returns true. But intersected() returns empty path. Everything works If I use rect with height = 1 instead of line. Maybe you have a better idea how to find intersection of QPainterPath with line? 回答1:

问题 I'm using a QPainter to get some graphics on a window. Unfortunately every time the paintEvent() function is called, the whole window is cleared. How can I draw without clearing? I.e. how do I leave the stuff from previous paint event untouched? I'm using Qt4 回答1: You need to set the backgroundMode by using the setBackgroundMode setter. The Qt::NoBackground enum is what you are searching for. 回答2: Since both replies are for Qt3 only, here is the solution for Qt4. You need to call setAttribute

问题 We know that for drawing on an image in qt, qpainter is used. Recently, I used drawLine() function to draw whatever an user is scribbling. This was done by passing the lastPoint and currentPoint from the mouseMoveEvent to a custom function which implements drawLine(). I have passed the arguments for that custom function as given below: void myPaint::mouseMoveEvent(QMouseEvent *event) { qDebug() << event->pos(); if ((event->buttons() & Qt::LeftButton) && scribbling) { pixelList.append(event-

问题 I'm using QPainter to draw multiline text on QImage. However, I also need to display a colored rectangle around each character's bounding box. So I need to know the bounding box that each character had when being drawn. For example, for painter.drawText(QRect(100, 100, 200, 200), Qt::TextWordWrap, "line\nline2", &r); I would need to get 10 rectangles, taking into account newlines, word-wrap, tabs, etc. For example, the rectangle of the second 'l' would be below the rectangle of the first 'l'

问题 4.7 and like to overlay two images on a qgraphicsview. The image on top shall be semi-transparent to allow to see through it. Initially both images are fully opaque. I expected some function for setting a global alpha-value for each pixel to exist, but it seems like there is no such function. The closest thing to it is QPixmap::setAlphaChannel(const QPixmap & alphaChannel), which, however, is marked as obsolete since Qt-4.6. Instead the manual refers to the CompositionModes of QPainter, but I