{"id":107082,"date":"2026-09-18T23:08:33","date_gmt":"2026-09-18T15:08:33","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/107082.html"},"modified":"2026-09-18T23:08:33","modified_gmt":"2026-09-18T15:08:33","slug":"qt-qpainter-2d-%e7%bb%98%e5%9b%be%e7%b3%bb%e7%bb%9f%e6%b7%b1%e5%ba%a6%e8%a7%a3%e6%9e%90%ef%bc%9a%e4%bb%8e%e7%94%bb%e7%ac%94%e5%88%b0%e6%b8%b2%e6%9f%93%e5%bc%95%e6%93%8e%e9%80%82","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/107082.html","title":{"rendered":"Qt QPainter 2D \u7ed8\u56fe\u7cfb\u7edf\u6df1\u5ea6\u89e3\u6790\uff1a\u4ece\u753b\u7b14\u5230\u6e32\u67d3\u5f15\u64ce\u9002"},"content":{"rendered":"

1. \u80cc\u666f<\/h2>\n

Qt \u7684 2D \u6e32\u67d3\u4f53\u7cfb\u81ea\u5e95\u5411\u4e0a\u5927\u81f4\u5206\u4e3a\u4e09\u5c42：<\/p>\n\n\n\u5c42\u7ea7\u7ec4\u4ef6\u5b9a\u4f4d<\/tr>\n\n\n\n
\u5e95\u5c42\u6e32\u67d3\u540e\u7aef<\/td>\nQPainter + QPaintDevice<\/td>\n\u76f4\u63a5\u7ed8\u5236 2D \u56fe\u5143（\u7ebf\u3001\u77e9\u5f62\u3001\u692d\u5706\u3001\u8def\u5f84\u3001\u6587\u5b57\u3001\u56fe\u50cf）\u5230\u4efb\u610f\u53ef\u7ed8\u8868\u9762<\/td>\n<\/tr>\n
\u4e2d\u95f4\u573a\u666f\u5c42<\/td>\nQGraphicsView \/ QGraphicsScene \/ QGraphicsItem<\/td>\n\u5728 QPainter \u4e4b\u4e0a\u5c01\u88c5\u573a\u666f-\u89c6\u56fe-\u56fe\u5143\u67b6\u6784，\u63d0\u4f9b\u5bf9\u8c61\u5316\u7ba1\u7406<\/td>\n<\/tr>\n
\u4e0a\u5c42\u58f0\u660e\u5f0f UI<\/td>\nQML \/ Qt Quick（Scene Graph）<\/td>\n\u58f0\u660e\u5f0f\u8bed\u8a00\u63cf\u8ff0\u754c\u9762，\u5e95\u5c42\u7528 GPU \u52a0\u901f\u7684\u573a\u666f\u56fe\u6e32\u67d3<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u4e3a\u4ec0\u4e48\u8fd8\u9700\u8981 QPainter？<\/p>\n

    \n
  • \u81ea\u5b9a\u4e49\u63a7\u4ef6（QWidget \u5b50\u7c7b）\u91cd\u5199\u00a0paintEvent\u00a0\u65f6，\u5b98\u65b9\u63a8\u8350\u65b9\u5f0f\u5c31\u662f QPainter；<\/li>\n
  • \u77e2\u91cf\u56fe\u5143\u3001\u7edf\u8ba1\u56fe\u3001\u6ce2\u5f62\u3001\u753b\u677f\u3001\u6d41\u7a0b\u56fe\u7b49"\u81ea\u7531\u753b\u5e03"\u573a\u666f，QPainter \u662f\u6700\u76f4\u63a5\u3001\u53ef\u9884\u6d4b\u7684 API；<\/li>\n
  • QGraphicsView\u3001QCustomPlot\u3001Qwt \u7b49\u4e0a\u5c42\u6846\u67b6，\u5185\u90e8\u6700\u7ec8\u90fd\u843d\u5230 QPainter \u7684 draw \u7cfb\u5217\u8c03\u7528；<\/li>\n
  • \u79bb\u5c4f\u6e32\u67d3（\u628a\u753b\u9762\u753b\u5230 QImage\/QPixmap \u518d\u590d\u7528）\u662f\u9ad8\u9891\u6027\u80fd\u4f18\u5316\u624b\u6bb5\u3002<\/li>\n<\/ul>\n
    \n

    2. \u6838\u5fc3 API \u8bf4\u660e<\/h3>\n

    2.1 QPainter \u751f\u547d\u5468\u671f<\/h4>\n

    \/\/ \u65b9\u5f0f\u4e00：\u6808\u4e0a\u6784\u9020\u5373 begin（\u5e38\u7528）
    \nvoid Widget::paintEvent(QPaintEvent*) {
    \n QPainter painter(this); \/\/ \u81ea\u52a8 begin(this)
    \n \/\/ … \u7ed8\u5236
    \n} \/\/ \u6790\u6784\u81ea\u52a8 end()<\/p>\n

    \/\/ \u65b9\u5f0f\u4e8c：\u663e\u5f0f begin\/end（\u7ed8\u5236\u5230\u975e QWidget \u8868\u9762\u6216\u4e2d\u9014\u5207\u6362\u8bbe\u5907\u65f6）
    \nQPainter painter;
    \npainter.begin(&image);
    \n\/\/ …
    \npainter.end();<\/p>\n

    \u5173\u952e\u6210\u5458：<\/p>\n\n\nAPI\u8bf4\u660e<\/tr>\n\n\n\n\n\n
    begin(QPaintDevice*)<\/td>\n\u5f00\u59cb\u7ed8\u5236，\u8fd4\u56de bool（\u8bbe\u5907\u4e0d\u652f\u6301\u65f6 false）<\/td>\n<\/tr>\n
    end()<\/td>\n\u7ed3\u675f\u7ed8\u5236；\u672a\u663e\u5f0f\u8c03\u7528\u65f6\u6790\u6784\u51fd\u6570\u81ea\u52a8\u8c03\u7528<\/td>\n<\/tr>\n
    isActive()<\/td>\n\u662f\u5426\u5904\u4e8e begin \u4e4b\u540e end \u4e4b\u524d<\/td>\n<\/tr>\n
    device()<\/td>\n\u5f53\u524d\u7ed8\u5236\u76ee\u6807\u8bbe\u5907<\/td>\n<\/tr>\n
    setRenderHint(QPainter::RenderHint, bool)<\/td>\n\u8bbe\u7f6e\u6e32\u67d3\u63d0\u793a，\u5982\u00a0Antialiasing（\u6297\u952f\u9f7f）<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    2.2 QPen（\u753b\u7b14：\u8f6e\u5ed3）<\/h4>\n

    QPen pen;
    \npen.setColor(QColor(220, 80, 80));
    \npen.setWidth(2); \/\/ \u50cf\u7d20\u5bbd\u5ea6（\u903b\u8f91\u5355\u4f4d，\u53d7\u53d8\u6362\u5f71\u54cd）
    \npen.setWidthF(1.5); \/\/ \u6d6e\u70b9\u5bbd\u5ea6
    \npen.setStyle(Qt::DashLine); \/\/ \u7ebf\u578b：SolidLine\/DashLine\/DotLine\/DashDotLine…
    \npen.setCapStyle(Qt::RoundCap); \/\/ \u7aef\u70b9\u5e3d：FlatCap\/SquareCap\/RoundCap
    \npen.setJoinStyle(Qt::RoundJoin); \/\/ \u8fde\u63a5\u70b9：BevelJoin\/MiterJoin\/RoundJoin
    \npainter.setPen(pen);<\/p>\n

    painter.setPen(QPen(Qt::blue, 0)); \/\/ \u5bbd\u5ea6 0 = cosmetic \u7b14（\u59cb\u7ec8 1 \u50cf\u7d20，\u4e0d\u968f\u7f29\u653e\u53d8\u7c97）
    \npainter.setPen(Qt::NoPen); \/\/ \u4e0d\u753b\u8f6e\u5ed3<\/p>\n

    2.3 QBrush（\u753b\u5237：\u586b\u5145）<\/h4>\n

    painter.setBrush(QBrush(QColor(100, 200, 150))); \/\/ \u7eaf\u8272
    \npainter.setBrush(Qt::BDiagPattern); \/\/ \u9884\u5b9a\u4e49\u56fe\u6848
    \npainter.setBrush(QBrush(QPixmap("texture.png"))); \/\/ \u7eb9\u7406\u586b\u5145
    \npainter.setBrush(Qt::NoBrush); \/\/ \u4e0d\u586b\u5145<\/p>\n

    \/\/ \u6e10\u53d8\u753b\u5237（\u89c1 2.6）
    \nQLinearGradient grad(0, 0, 200, 200);
    \ngrad.setColorAt(0.0, Qt::white);
    \ngrad.setColorAt(1.0, QColor(40, 120, 200));
    \npainter.setBrush(QBrush(grad));<\/p>\n

    2.4 draw \u7cfb\u5217\u56fe\u5143 API<\/h4>\n\n\nAPI\u4f5c\u7528<\/tr>\n\n\n\n\n\n\n\n\n\n\n
    drawPoint \/ drawPoints<\/td>\n\u70b9<\/td>\n<\/tr>\n
    drawLine \/ drawLines \/ drawPolyline<\/td>\n\u7ebf \/ \u6298\u7ebf<\/td>\n<\/tr>\n
    drawRect \/ drawRoundedRect<\/td>\n\u77e9\u5f62 \/ \u5706\u89d2\u77e9\u5f62<\/td>\n<\/tr>\n
    drawEllipse \/ drawArc \/ drawChord \/ drawPie<\/td>\n\u692d\u5706 \/ \u5f27 \/ \u5f13\u5f62 \/ \u6247\u5f62<\/td>\n<\/tr>\n
    drawPolygon<\/td>\n\u591a\u8fb9\u5f62（\u81ea\u52a8\u95ed\u5408）<\/td>\n<\/tr>\n
    drawPath(QPainterPath)<\/td>\n\u4efb\u610f\u8def\u5f84（\u89c1 2.5）<\/td>\n<\/tr>\n
    drawText(QRect, int flags, QString)<\/td>\n\u6587\u672c（\u89c1 2.7）<\/td>\n<\/tr>\n
    drawPixmap \/ drawImage<\/td>\n\u56fe\u50cf（\u89c1 2.8）<\/td>\n<\/tr>\n
    fillRect(QRect, QBrush\/QColor)<\/td>\n\u76f4\u63a5\u586b\u5145\u77e9\u5f62（\u4e0d\u8d70 pen）<\/td>\n<\/tr>\n
    eraseRect<\/td>\n\u64e6\u9664（\u4e0d\u63a8\u8350，\u7528 fillRect \u66ff\u4ee3）<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    \u6240\u6709 draw \u5747\u540c\u65f6\u53d7\u5f53\u524d pen（\u8f6e\u5ed3）\u4e0e brush（\u586b\u5145）\u5f71\u54cd\u3002<\/p>\n

    2.5 QPainterPath（\u8def\u5f84）<\/h4>\n

    QPainterPath path;
    \npath.moveTo(50, 50); \/\/ \u79fb\u52a8\u8d77\u70b9
    \npath.lineTo(150, 50); \/\/ \u76f4\u7ebf
    \npath.quadTo(200, 0, 250, 80); \/\/ \u4e8c\u6b21\u8d1d\u585e\u5c14
    \npath.cubicTo(300, 160, 100, 200, 80, 120); \/\/ \u4e09\u6b21\u8d1d\u585e\u5c14
    \npath.arcTo(QRectF(20, 20, 100, 100), 0, 180); \/\/ \u5706\u5f27
    \npath.closeSubpath(); \/\/ \u95ed\u5408\u5f53\u524d\u5b50\u8def\u5f84<\/p>\n

    path.addRect(…); \/\/ \u6dfb\u52a0\u5b50\u8def\u5f84
    \npath.addEllipse(…);
    \npath.addRoundedRect(…);
    \npath.addText(QPointF, font, "Qt");<\/p>\n

    painter.drawPath(path);<\/p>\n

    \/\/ \u5e38\u7528\u8c13\u8bcd
    \npath.isEmpty(); path.contains(QPointF); path.boundingRect();
    \n\/\/ \u5e03\u5c14\u8fd0\u7b97（Qt 5.10+ \u9700\u8981 QtGui \u9644\u52a0\u6a21\u5757\u8def\u5f84\u652f\u6301）
    \nQPainterPath united = path1.united(path2); \/\/ \u5e76\u96c6
    \nQPainterPath inter = path1.intersected(path2); \/\/ \u4ea4\u96c6
    \nQPainterPath diff = path1.subtracted(path2); \/\/ \u5dee\u96c6<\/p>\n

    2.6 QGradient（\u6e10\u53d8）<\/h4>\n

    \u4e09\u79cd\u5185\u7f6e\u6e10\u53d8 + \u4e00\u4e2a\u901a\u7528\u57fa\u7c7b：<\/p>\n\n\n\u7c7b\u578b\u6784\u9020\u8981\u70b9\u793a\u4f8b<\/tr>\n\n\n\n
    QLinearGradient(x1,y1,x2,y2)<\/td>\n\u8d77\u70b9\/\u7ec8\u70b9\u5b9a\u4e49\u65b9\u5411<\/td>\n\u9ad8\u5149\u3001\u8fdb\u5ea6\u6761<\/td>\n<\/tr>\n
    QRadialGradient(cx,cy,r)<\/td>\n\u5706\u5fc3+\u534a\u5f84<\/td>\n\u5149\u6655\u3001\u7403\u4f53<\/td>\n<\/tr>\n
    QConicalGradient(cx,cy,angle)<\/td>\n\u5706\u5fc3+\u8d77\u59cb\u89d2<\/td>\n\u4eea\u8868\u76d8\u3001\u8c03\u8272\u73af<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    QLinearGradient g(0, 0, width(), 0); \/\/ \u6c34\u5e73\u6e10\u53d8
    \ng.setColorAt(0.0, QColor(255, 0, 0));
    \ng.setColorAt(0.5, QColor(0, 255, 0));
    \ng.setColorAt(1.0, QColor(0, 0, 255));
    \ng.setSpread(QGradient::RepeatSpread); \/\/ \u8d85\u51fa\u8303\u56f4\u540e\u7684\u6269\u6563\u65b9\u5f0f
    \npainter.setBrush(g);<\/p>\n

    2.7 \u6587\u5b57\u7ed8\u5236<\/h4>\n

    QFont font("Microsoft YaHei", 12); \/\/ \u6ce8\u610f\u5b57\u4f53\u540d\u8981\u5b58\u5728\u4e8e\u7cfb\u7edf
    \nfont.setBold(true);
    \npainter.setFont(font);
    \npainter.setPen(Qt::black);<\/p>\n

    painter.drawText(QPoint(10, 30), "\u5de6\u4e0a\u89d2\u57fa\u7ebf\u6587\u672c");<\/p>\n

    painter.drawText(rect, Qt::AlignCenter | Qt::TextWordWrap, "\u5c45\u4e2d\u6362\u884c\u6587\u672c");
    \n\/\/ \u8fd4\u56de\u5b9e\u9645\u7ed8\u5236\u5230\u7684\u77e9\u5f62（\u53ef\u7528\u6765\u6d4b\u6587\u672c\u5c3a\u5bf8）
    \nQRectF br;
    \npainter.drawText(rect, Qt::AlignCenter, "\u6587\u672c", &br);<\/p>\n

    QFontMetrics fm(painter.font()); \/\/ \u5b57\u4f53\u5ea6\u91cf
    \nint w = fm.horizontalAdvance("\u6587\u672c"); \/\/ \u6587\u672c\u50cf\u7d20\u5bbd\u5ea6（Qt5.11+；\u65e7\u7248\u7528 width()）
    \nint h = fm.height(); \/\/ \u884c\u9ad8<\/p>\n

    2.8 \u56fe\u50cf\u7ed8\u5236<\/h4>\n

    painter.drawPixmap(x, y, pixmap); \/\/ \u539f\u5c3a\u5bf8
    \npainter.drawPixmap(QRect(x,y,w,h), pixmap); \/\/ \u62c9\u4f38\u5230\u76ee\u6807\u77e9\u5f62
    \npainter.drawPixmap(QRect(x,y,w,h), pixmap, QRectF(src)); \/\/ \u5e26\u6e90\u533a\u57df\u622a\u53d6
    \npainter.drawImage(QRect(x,y,w,h), image); \/\/ QImage \u540c\u7406<\/p>\n

    \/\/ \u5e73\u6ed1\u7f29\u653e
    \npainter.setRenderHint(QPainter::SmoothPixmapTransform, true);<\/p>\n

    2.9 \u5750\u6807\u7cfb\u7edf\u4e0e\u53d8\u6362<\/h4>\n

    QPainter \u9ed8\u8ba4\u5750\u6807\u7cfb：\u539f\u70b9\u5728\u8bbe\u5907\u5de6\u4e0a\u89d2，x \u5411\u53f3，y \u5411\u4e0b，\u5355\u4f4d\u662f\u903b\u8f91\u50cf\u7d20\u3002<\/p>\n

    painter.translate(100, 50); \/\/ \u5e73\u79fb
    \npainter.rotate(45); \/\/ \u65cb\u8f6c（\u5ea6，\u987a\u65f6\u9488）
    \npainter.scale(2.0, 2.0); \/\/ \u7f29\u653e
    \npainter.shear(0.1, 0); \/\/ \u9519\u5207<\/p>\n

    \/\/ \u5fc5\u987b\u6210\u5bf9\u4f7f\u7528，\u5426\u5219\u53d8\u6362\u53e0\u52a0\u6c61\u67d3\u540e\u7eed\u7ed8\u5236
    \npainter.save();
    \npainter.translate(cx, cy);
    \npainter.rotate(angle);
    \npainter.drawText(QPointF(0, -10), "\u6807\u7b7e");
    \npainter.restore();<\/p>\n

    \/\/ \u4e16\u754c\u53d8\u6362\u77e9\u9635（Qt 5.14+ \u63d0\u4f9b\u66f4\u7cbe\u786e\u7684 QTransform \u91cd\u8f7d）
    \nQTransform t;
    \nt.translate(50, 50).rotate(30).scale(1.5, 1.5);
    \npainter.setWorldTransform(t);
    \npainter.resetTransform(); \/\/ \u91cd\u7f6e\u4e3a\u5355\u4f4d\u77e9\u9635<\/p>\n

    \u89c6\u56fe\u53d8\u6362（Qt 5.14+）：setViewport\u00a0\/\u00a0setWindow\u00a0\u5141\u8bb8\u628a\u903b\u8f91\u7a97\u53e3\u6620\u5c04\u5230\u8bbe\u5907\u89c6\u53e3，\u9002\u5408\u56fa\u5b9a\u903b\u8f91\u5750\u6807\u7cfb\u7684\u7ed8\u56fe（\u5982\u66f2\u7ebf\u56fe y \u8f74\u8303\u56f4\u56fa\u5b9a）：<\/p>\n

    painter.setWindow(QRect(0, 0, 1000, 500)); \/\/ \u903b\u8f91\u7a97\u53e3
    \npainter.setViewport(QRect(0, 0, width(), height())); \/\/ \u7269\u7406\u533a\u57df
    \n\/\/ \u6b64\u540e\u6240\u6709\u5750\u6807\u6309 1000×500 \u903b\u8f91\u7a7a\u95f4\u4e66\u5199，\u81ea\u52a8\u6620\u5c04<\/p>\n

    2.10 \u79bb\u5c4f\u6e32\u67d3\u4e0e\u7f13\u5b58<\/h4>\n

    \/\/ \u5e38\u7528\u7f13\u5b58\u8f7d\u4f53
    \nQPixmap pm(size); \/\/ \u5c4f\u5e55\u4f18\u5316，\u7ed8\u5236\u5728\u5c4f\u5e55\u5173\u8054\u8bbe\u5907\u4e0a\u6700\u5feb（\u4f9d\u8d56\u5e73\u53f0）
    \nQImage img(size, QImage::Format_ARGB32_Premultiplied); \/\/ \u50cf\u7d20\u53ef\u76f4\u8bfb，\u9002\u5408 CPU \u5904\u7406\/\u4fdd\u5b58
    \nQPicture pic; \/\/ \u8bb0\u5f55\u7ed8\u5236\u6307\u4ee4（\u77e2\u91cf），\u53ef\u91cd\u653e<\/p>\n

    \/\/ \u79bb\u5c4f\u7ed8\u5236\u6807\u51c6\u59ff\u52bf
    \nQPixmap pm(size);
    \npm.fill(Qt::transparent); \/\/ \u5148\u586b\u5145\u900f\u660e，\u5426\u5219\u521d\u59cb\u5185\u5bb9\u672a\u5b9a\u4e49
    \nQPainter p(&pm);
    \np.setRenderHint(QPainter::Antialiasing);
    \n\/\/ … \u7ed8\u5236
    \np.end();<\/p>\n

    \/\/ \u4e4b\u540e\u5728 paintEvent \u4e2d blit \u4e0a\u5c4f
    \npainter.drawPixmap(0, 0, pm);<\/p>\n

    \/\/ QImage \u9010\u50cf\u7d20\u5904\u7406\u793a\u4f8b
    \nQImage img(400, 300, QImage::Format_ARGB32_Premultiplied);
    \nimg.fill(Qt::white);
    \nfor (int y = 0; y < img.height(); ++y)
    \n for (int x = 0; x < img.width(); ++x)
    \n img.setPixelColor(x, y, QColor(x % 256, y % 256, 128));
    \nimg.save("out.png"); \/\/ \u652f\u6301 png\/jpg\/bmp \u7b49（\u6309\u540e\u7f00\u9009\u683c\u5f0f）<\/p>\n

    2.11 \u7ec4\u5408\u6a21\u5f0f（Composition Mode，Qt 4.6+）<\/h4>\n

    painter.setCompositionMode(QPainter::CompositionMode_SourceOver); \/\/ \u9ed8\u8ba4
    \npainter.setCompositionMode(QPainter::CompositionMode_Source); \/\/ \u76f4\u63a5\u8986\u76d6
    \npainter.setCompositionMode(QPainter::CompositionMode_Plus); \/\/ \u53e0\u52a0\u589e\u4eae
    \npainter.setCompositionMode(QPainter::CompositionMode_DestinationOver);
    \n\/\/ … \u5171 30 \u79cd\u6a21\u5f0f，\u9002\u5408\u5b9e\u73b0\u6a61\u76ae\u64e6\u3001\u53d1\u5149\u3001\u906e\u7f69\u7b49\u6548\u679c
    \n\/\/ \u6a61\u76ae\u64e6\u5e38\u7528：\u5148\u8bbe\u7f6e Source \u6a21\u5f0f，\u518d\u7528\u900f\u660e\u8272\u7ed8\u5236
    \npainter.setCompositionMode(QPainter::CompositionMode_Clear);
    \npainter.fillRect(rect, Qt::transparent);
    \npainter.setCompositionMode(QPainter::CompositionMode_SourceOver);<\/p>\n

    \n

    3. \u8be6\u7ec6\u4f7f\u7528\u8bf4\u660e<\/h3>\n

    3.1 \u6700\u5c0f\u53ef\u8fd0\u884c\u793a\u4f8b：\u5e26\u6e10\u53d8\u4e0e\u6297\u952f\u9f7f\u7684\u81ea\u5b9a\u4e49\u63a7\u4ef6<\/h4>\n

    \/\/ widget.h
    \n#ifndef WIDGET_H
    \n#define WIDGET_H
    \n#include <QWidget>
    \nclass Widget : public QWidget {
    \n Q_OBJECT
    \npublic:
    \n explicit Widget(QWidget *parent = nullptr);
    \nprotected:
    \n void paintEvent(QPaintEvent *event) override;
    \n};
    \n#endif<\/p>\n

    \/\/ widget.cpp
    \n#include "widget.h"
    \n#include <QPainter>
    \n#include <QPainterPath>
    \n#include <QLinearGradient><\/p>\n

    Widget::Widget(QWidget *parent) : QWidget(parent) {
    \n setMinimumSize(400, 300);
    \n}<\/p>\n

    void Widget::paintEvent(QPaintEvent *) {
    \n QPainter p(this);
    \n p.setRenderHint(QPainter::Antialiasing, true); \/\/ \u6297\u952f\u9f7f，\u753b\u66f2\u7ebf\u5fc5\u5907<\/p>\n

    \/\/ 1) \u6e10\u53d8\u5706\u89d2\u77e9\u5f62
    \n QLinearGradient grad(0, 0, width(), height());
    \n grad.setColorAt(0.0, QColor(70, 130, 220));
    \n grad.setColorAt(1.0, QColor(30, 60, 130));
    \n p.setBrush(grad);
    \n p.setPen(QPen(Qt::white, 2));
    \n p.drawRoundedRect(rect().adjusted(10, 10, -10, -10), 12, 12);<\/p>\n

    \/\/ 2) \u8d1d\u585e\u5c14\u66f2\u7ebf\u8def\u5f84
    \n QPainterPath curve;
    \n curve.moveTo(20, 200);
    \n curve.cubicTo(120, 40, 280, 260, 380, 120);
    \n p.setPen(QPen(QColor(255, 220, 100), 3));
    \n p.setBrush(Qt::NoBrush);
    \n p.drawPath(curve);<\/p>\n

    \/\/ 3) \u5c45\u4e2d\u6587\u6848
    \n p.setPen(Qt::white);
    \n p.setFont(QFont("Microsoft YaHei", 14, QFont::Bold));
    \n p.drawText(rect(), Qt::AlignCenter, "Hello QPainter");
    \n}<\/p>\n

    3.2 \u5750\u6807\u53d8\u6362\u5b9e\u6218：\u7ed8\u5236\u65cb\u8f6c\u7684\u98ce\u6247\u53f6\u7247<\/h4>\n

    void FanWidget::paintEvent(QPaintEvent *) {
    \n QPainter p(this);
    \n p.setRenderHint(QPainter::Antialiasing);
    \n const QPointF c = rect().center();
    \n const int n = 3;
    \n for (int i = 0; i < n; ++i) {
    \n p.save(); \/\/ \u4fdd\u5b58\u672a\u53d8\u6362\u72b6\u6001
    \n p.translate(c); \/\/ \u5e73\u79fb\u5230\u4e2d\u5fc3
    \n p.rotate(angle_ + i * 360.0 \/ n); \/\/ \u65cb\u8f6c
    \n p.setBrush(QColor(80, 160, 255, 180));
    \n p.setPen(Qt::NoPen);
    \n p.drawEllipse(QRectF(-90, -20, 180, 40)); \/\/ \u4ee5\u539f\u70b9\u4e3a\u4e2d\u5fc3\u7684\u53f6\u7247
    \n p.restore(); \/\/ \u6062\u590d，\u907f\u514d\u65cb\u8f6c\u53e0\u52a0
    \n }
    \n}<\/p>\n

    \u8981\u70b9：\u6bcf\u6b21\u53d8\u6362\u524d save\u3001\u7ed3\u675f\u540e restore，\u5426\u5219\u7b2c\u4e8c\u6b21\u5faa\u73af\u7684 rotate \u4f1a\u5728\u7b2c\u4e00\u6b21\u57fa\u7840\u4e0a\u53e0\u52a0，\u53f6\u7247\u4f1a\u8d8a\u8f6c\u8d8a\u6b6a\u3002<\/p>\n

    3.3 \u79bb\u5c4f\u6e32\u67d3 + \u7f13\u5b58：\u62d6\u52a8\u4e0d\u95ea\u70c1\u7684\u753b\u677f<\/h4>\n

    class BoardWidget : public QWidget {
    \n QPixmap canvas_;
    \n QPoint last_;
    \nprotected:
    \n void paintEvent(QPaintEvent *) override {
    \n QPainter p(this);
    \n p.drawPixmap(0, 0, canvas_); \/\/ \u6bcf\u6b21\u91cd\u7ed8\u53ea\u9700 blit \u7f13\u5b58
    \n }
    \n void mousePressEvent(QMouseEvent *e) override {
    \n last_ = e->pos();
    \n }
    \n void mouseMoveEvent(QMouseEvent *e) override {
    \n QPainter p(&canvas_); \/\/ \u76f4\u63a5\u5728\u7f13\u5b58\u4e0a\u7ed8\u5236
    \n p.setPen(QPen(Qt::black, 2, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
    \n p.drawLine(last_, e->pos());
    \n last_ = e->pos();
    \n update(); \/\/ \u89e6\u53d1\u91cd\u7ed8，paintEvent \u4e2d blit
    \n }
    \n void resizeEvent(QResizeEvent *e) override {
    \n QPixmap next(size());
    \n next.fill(Qt::white);
    \n QPainter p(&next);
    \n p.drawPixmap(0, 0, canvas_); \/\/ \u4fdd\u7559\u65e7\u5185\u5bb9
    \n canvas_ = next;
    \n QWidget::resizeEvent(e);
    \n }
    \n};<\/p>\n

    \u8fd9\u662f\u767d\u677f\/\u6d82\u9e26\u7c7b\u5e94\u7528\u7684\u6807\u51c6\u67b6\u6784：\u4ea4\u4e92\u7ed8\u5236\u5230\u79bb\u5c4f\u7f13\u5b58，paintEvent \u53ea\u505a blit，\u5929\u7136\u9632\u95ea\u70c1\u3001\u6027\u80fd\u9ad8\u3002<\/p>\n

    3.4 \u7b80\u5355\u67f1\u72b6\u56fe（QPainter \u624b\u5199\u56fe\u8868）<\/h4>\n

    void ChartWidget::paintEvent(QPaintEvent *) {
    \n QPainter p(this);
    \n p.setRenderHint(QPainter::Antialiasing);
    \n const QVector<double> data{42, 78, 55, 91, 66};
    \n const int n = data.size();
    \n const double bw = width() \/ double(n) * 0.6; \/\/ \u67f1\u5bbd
    \n const double maxV = 100.0;<\/p>\n

    \/\/ \u5750\u6807\u8f74
    \n p.setPen(QPen(Qt::gray, 1));
    \n p.drawLine(QPointF(20, height() – 20), QPointF(width() – 10, height() – 20));
    \n p.drawLine(QPointF(20, height() – 20), QPointF(20, 10));<\/p>\n

    \/\/ \u67f1\u4f53（\u9876\u90e8\u6e10\u53d8）
    \n for (int i = 0; i < n; ++i) {
    \n double h = data[i] \/ maxV * (height() – 60);
    \n double x = 30 + i * (width() – 40) \/ n + (width() – 40) \/ n * 0.2;
    \n QRectF bar(x, height() – 20 – h, bw, h);
    \n QLinearGradient g(bar.topLeft(), bar.bottomLeft());
    \n g.setColorAt(0, QColor(90, 170, 255));
    \n g.setColorAt(1, QColor(40, 90, 200));
    \n p.setBrush(g);
    \n p.setPen(Qt::NoPen);
    \n p.drawRoundedRect(bar, 3, 3);
    \n \/\/ \u6570\u503c\u6807\u7b7e
    \n p.setPen(Qt::black);
    \n p.drawText(bar.adjusted(0, -22, 0, -6), Qt::AlignCenter, QString::number(data[i]));
    \n }
    \n}<\/p>\n

    \n

    4. \u5e38\u9519\u70b9 \/ \u5751（\u9ad8\u53d1\u6e05\u5355）<\/h3>\n

    4.1 \u91cd\u590d begin \u5bfc\u81f4\u8b66\u544a\u6216\u5d29\u6e83<\/h4>\n

    \u7528\u00a0QPainter p(this)\u00a0\u540e\u53c8\u5728\u51fd\u6570\u91cc\u8c03\u7528\u00a0p.begin(…)，\u6216\u5bf9\u5df2 begin \u7684 painter \u518d\u6b21 begin，\u4f1a\u8f93\u51fa\u00a0QPainter::begin: Painter already active\u00a0\u4e14\u8fd4\u56de false\u3002\u89c4\u5219：\u6808\u4e0a\u6784\u9020\u5373 begin，\u4e4b\u540e\u53ea\u51c6 end \u4e00\u6b21（\u53ef\u7701\u7565）；\u9700\u8981\u5207\u6362\u8bbe\u5907\u65f6\u7528\u65e0\u53c2\u6784\u9020 + \u663e\u5f0f begin\u3002<\/p>\n

    4.2 \u5728 paintEvent \u4e4b\u5916\u7ed8\u5236 QWidget \u4e0d\u751f\u6548<\/h4>\n

    QWidget \u7684\u5185\u5bb9\u7ed8\u5236\u53ea\u80fd\u53d1\u751f\u5728 paintEvent \u4e2d（\u7cfb\u7edf\u968f\u65f6\u4f1a\u64e6\u9664\u91cd\u753b）\u3002\u60f3\u4e3b\u52a8\u91cd\u753b\u8c03\u7528\u00a0update()（\u5408\u5e76\u8bf7\u6c42）\u6216\u00a0repaint()（\u7acb\u5373\u91cd\u753b，\u963b\u585e，\u614e\u7528）\u3002\u975e paintEvent \u4e2d\u753b widget \u7684\u6b63\u786e\u505a\u6cd5：\u753b\u5230\u79bb\u5c4f QPixmap\/QImage，\u518d\u5728 paintEvent \u91cc blit\u3002<\/p>\n

    4.3 \u53d8\u6362\u672a save\/restore \u5bfc\u81f4\u6c61\u67d3<\/h4>\n

    translate\/rotate\/scale \u662f\u6709\u72b6\u6001\u7684，\u4f1a\u5f71\u54cd\u5176\u540e\u7684\u6240\u6709\u7ed8\u5236\u3002\u5fd8\u8bb0 restore \u7684\u5178\u578b\u75c7\u72b6：\u7b2c\u4e8c\u6b21\u5237\u65b0\u753b\u9762\u4f4d\u7f6e\u8d8a\u504f\u8d8a\u8fdc\u3001\u56fe\u5f62\u8d8a\u6765\u8d8a\u5c0f\/\u5927\u3002\u6bcf\u4e2a\u53d8\u6362\u5757\u524d\u540e\u5fc5\u987b save()\/restore() \u914d\u5bf9\u3002<\/p>\n

    4.4 \u9ad8 DPI \/ \u7f29\u653e\u6a21\u7cca<\/h4>\n
      \n
    • \u672a\u542f\u7528\u9ad8 DPI \u652f\u6301\u65f6，\u9ad8\u5206\u5c4f\u4e0a QPainter \u753b\u7684\u6587\u5b57\/\u7ebf\u6761\u53d1\u865a：\u7a0b\u5e8f\u5165\u53e3\u52a0\u00a0QApplication::setHighDpiScaleFactorRoundingPolicy(…)，\u5e76\u5728 main \u6700\u524d\u9762\u00a0QGuiApplication::setAttribute(Qt::AA_EnableHighDpiScaling)（Qt 5；Qt 6 \u9ed8\u8ba4\u5f00\u542f）\u3002<\/li>\n
    • \u56fe\u7247\u62c9\u4f38\u6a21\u7cca：\u9700\u8981\u00a0SmoothPixmapTransform\u00a0\u6e32\u67d3\u63d0\u793a\u3002<\/li>\n
    • \u7ebf\u6761\u968f\u7f29\u653e\u53d8\u7c97：\u60f3\u8981\u6052 1 \u50cf\u7d20\u7528\u5bbd\u5ea6 0（cosmetic pen）\u3002<\/li>\n<\/ul>\n

      4.5 \u4e2d\u6587\u4e71\u7801 \/ \u5b57\u4f53\u7f3a\u5931<\/h4>\n
        \n
      • \u660e\u786e\u8bbe\u7f6e\u4e2d\u6587\u5b57\u4f53：QFont("Microsoft YaHei")\u00a0\u6216\u00a0"SimHei"，\u4e0d\u8981\u4f9d\u8d56\u9ed8\u8ba4\u5b57\u4f53；<\/li>\n
      • \u7cfb\u7edf\u65e0\u8be5\u5b57\u4f53\u65f6 Qt \u4f1a\u56de\u9000，\u53ef\u80fd\u663e\u793a\u8c46\u8150\u5757；<\/li>\n
      • \u753b\u5e03\u63a7\u4ef6\u8bbe\u7f6e\u5b57\u4f53\u540e\u8bb0\u5f97\u00a0painter.setFont(font)，painter \u4e0d\u4f1a\u81ea\u52a8\u7ee7\u627f widget \u5b57\u4f53\u3002<\/li>\n<\/ul>\n

        4.6 \u6027\u80fd\u9677\u9631<\/h4>\n
          \n
        • \u5728 paintEvent \u4e2d\u521b\u5efa\u6e10\u53d8\/\u5b57\u4f53\/\u5927\u5bf9\u8c61：\u6bcf\u6b21\u91cd\u7ed8\u90fd\u91cd\u5efa\u3002\u5e94\u5728\u6784\u9020\u51fd\u6570\u7f13\u5b58\u4e3a\u6210\u5458\u53d8\u91cf\u3002<\/li>\n
        • \u6297\u952f\u9f7f\u5168\u5f00：\u5706\u89d2+\u6e10\u53d8+\u9634\u5f71\u53e0\u52a0\u65f6 CPU \u5f00\u9500\u663e\u8457，\u53ea\u6709\u66f2\u7ebf\/\u659c\u7ebf\u9700\u8981\u65f6\u5f00\u542f，\u77e9\u5f62\/\u6587\u5b57\u53ef\u4e0d\u5f00\u3002<\/li>\n
        • \u9891\u7e41 update() \u9020\u6210\u8fde\u7eed\u91cd\u7ed8：\u5408\u5e76\u4e3a\u5b9a\u65f6\u5668\u8282\u6d41（\u5982 30ms \u4e00\u6b21）\u3002<\/li>\n
        • \u5927 QPixmap \u53cd\u590d\u7ed8\u5236：\u7528\u00a0drawTiledPixmap\u00a0\u5e73\u94fa\u6216\u7f29\u5c0f\u76ee\u6807\u533a\u57df\u3002<\/li>\n
        • QImage \u9010\u50cf\u7d20 setPixelColor \u5f88\u6162：\u6279\u91cf\u7528\u00a0setPixelColor\u00a0\u5faa\u73af 1000×1000 \u7ea6\u9700\u51e0\u5341 ms \u7ea7；\u9700\u8981\u9ad8\u6027\u80fd\u56fe\u50cf\u5904\u7406\u4f18\u5148\u64cd\u4f5c\u00a0bits()\/scanLine()\u00a0\u6307\u9488\u6216\u6539\u7528 GPU \u65b9\u6848\u3002<\/li>\n<\/ul>\n

          4.7 QPixmap \u672a\u586b\u5145\u5c31\u7ed8\u5236<\/h4>\n

          QPixmap pm(size)\u00a0\u521d\u59cb\u5185\u5bb9\u672a\u5b9a\u4e49（\u53d6\u51b3\u4e8e\u5e73\u53f0，\u53ef\u80fd\u662f\u5783\u573e\u6570\u636e）\u3002\u79bb\u5c4f\u7ed8\u5236\u524d\u5fc5\u987b\u5148\u00a0pm.fill(Qt::transparent)\u00a0\u6216\u586b\u5145\u5e95\u8272，\u5426\u5219\u51fa\u73b0\u82b1\u5c4f\/\u9ed1\u8fb9\u3002<\/p>\n

          4.8 QImage \u683c\u5f0f\u9009\u62e9\u9519\u8bef<\/h4>\n
            \n
          • Format_ARGB32\u00a0\u662f\u4e0d\u9884\u4e58 alpha，Format_ARGB32_Premultiplied\u00a0\u662f\u9884\u4e58，\u4e8c\u8005\u6df7\u7528\u4f1a\u5bfc\u81f4\u989c\u8272\u53d1\u6697\/\u53d1\u4eae；<\/li>\n
          • \u9ed8\u8ba4\u00a0Format_ARGB32（Qt 5 \u4e2d QImage \u9ed8\u8ba4\u5c31\u662f\u5b83）\u5728\u90e8\u5206\u7ed8\u5236\u64cd\u4f5c\u4e0a\u6bd4\u9884\u4e58\u6162；\u9700\u8981 alpha \u5408\u6210\u5efa\u8bae\u7528\u00a0Premultiplied；<\/li>\n
          • Format_RGB32\u00a0\u65e0 alpha，pixelColor\u00a0\u8bfb alpha \u6052\u4e3a 255\u3002<\/li>\n<\/ul>\n

            4.9 \u7ebf\u7a0b\u7ed8\u5236\u5b89\u5168<\/h4>\n

            QPainter \u7ed8\u5236\u00a0QImage\u00a0\u662f\u7ebf\u7a0b\u5b89\u5168\u7684（\u53ea\u8981\u8be5 QImage \u4e0d\u88ab\u5176\u5b83\u7ebf\u7a0b\u540c\u65f6\u8bfb\u5199），\u4f46\u7ed8\u5236\u00a0QPixmap \/ QWidget\u00a0\u4e0d\u662f\u3002\u540e\u53f0\u7ebf\u7a0b\u753b\u56fe\u8bf7\u7528 QImage，\u5b8c\u6210\u540e\u901a\u8fc7\u4fe1\u53f7\u69fd\u628a\u7ed3\u679c\u4ea4\u7ed9 GUI \u7ebf\u7a0b\u518d\u8f6c QPixmap \u4e0a\u5c4f\u3002<\/p>\n

            4.10 drawText \u5bf9\u4e0d\u9f50 \/ \u6d4b\u91cf\u8bef\u5dee<\/h4>\n
              \n
            • drawText(QPoint, …)\u00a0\u7684 y \u662f\u57fa\u7ebf（baseline）\u5750\u6807，\u4e0d\u662f\u6587\u5b57\u9876\u90e8，\u7b2c\u4e00\u773c\u89c9\u5f97"\u504f\u4e0a\u4e86"\u662f\u6b63\u5e38\u7684；<\/li>\n
            • \u60f3\u8981\u7cbe\u786e\u5c45\u4e2d\u7528\u00a0drawText(QRect, Qt::AlignCenter, …)；<\/li>\n
            • \u5bbd\u5ea6\u6d4b\u91cf\u7528\u00a0QFontMetrics::horizontalAdvance（\u4e0d\u8981\u7528\u5e9f\u5f03\u7684\u00a0width()，\u591a\u5b57\u8282\u5b57\u7b26\u4f1a\u504f\u5c0f）\u3002<\/li>\n<\/ul>\n

              4.11 \u7ec4\u5408\u6a21\u5f0f\u72b6\u6001\u6cc4\u6f0f<\/h4>\n

              \u8bbe\u7f6e\u4e86\u00a0CompositionMode_Clear\u00a0\u6216\u00a0Source\u00a0\u540e\u5fd8\u8bb0\u6062\u590d\u00a0SourceOver，\u540e\u7eed\u6240\u6709\u7ed8\u5236\u90fd\u4f1a\u53d8\u6210\u8986\u76d6\/\u64e6\u9664\u6548\u679c\u3002\u6539\u7ec4\u5408\u6a21\u5f0f\u540c\u6837\u5efa\u8bae save\/restore \u5305\u88f9\u3002<\/p>\n

              4.12 resizeEvent \u4e2d\u672a\u4fdd\u7559\u753b\u677f\u5185\u5bb9<\/h4>\n

              \u753b\u677f\u7c7b\u63a7\u4ef6 resize \u540e QPixmap \u5c3a\u5bf8\u53d8\u5316，\u76f4\u63a5 new \u4e00\u5757\u7a7a\u7684\u4f1a\u628a\u65e7\u5185\u5bb9\u6e05\u6389；\u5e94\u6309 3.3 \u793a\u4f8b\u628a\u65e7\u753b\u5e03\u5185\u5bb9\u590d\u5236\u5230\u65b0\u753b\u5e03\u3002<\/p>\n

              \n

              5. \u603b\u7ed3<\/h3>\n

              QPainter \u662f Qt 2D \u7ed8\u5236\u7684\u6839：\u81ea\u5b9a\u4e49\u63a7\u4ef6\u3001\u79bb\u5c4f\u6e32\u67d3\u3001\u56fe\u8868\u3001\u753b\u677f\u3001\u751a\u81f3\u4e0a\u5c42 Graphics View \/ QCustomPlot \/ QML \u573a\u666f\u56fe，\u5e95\u5c42\u90fd\u79bb\u4e0d\u5f00\u5b83\u3002\u638c\u63e1\u5b83\u7684\u5173\u952e\u662f\u7406\u89e3\u4e09\u4ef6\u4e8b：<\/p>\n

            • \u72b6\u6001\u673a\u6a21\u578b：pen\/brush\/font\/transform\/renderHint \u90fd\u662f"\u5f53\u524d\u72b6\u6001"，\u7ed8\u5236\u51fd\u6570\u5373\u65f6\u6d88\u8d39\u5f53\u524d\u72b6\u6001\u2014\u2014\u6240\u4ee5 save\/restore \u662f\u63a7\u5236\u72b6\u6001\u6c61\u67d3\u7684\u552f\u4e00\u53ef\u9760\u624b\u6bb5；<\/li>\n
            • \u8bbe\u5907\u65e0\u5173：QPainter \u53ef\u4ee5\u753b\u5230 QWidget\/QPixmap\/QImage\/QPicture \u4efb\u610f\u8bbe\u5907，\u8fd9\u4e00\u62bd\u8c61\u8ba9"\u79bb\u5c4f\u7f13\u5b58 + \u4e0a\u5c4f blit"\u6210\u4e3a\u6027\u80fd\u4f18\u5316\u7684\u4e07\u80fd\u94a5\u5319；<\/li>\n
            • \u5750\u6807\u53d8\u6362：translate\/rotate\/scale \u662f\u7ed8\u5236\u590d\u6742\u56fe\u5f62（\u4eea\u8868\u3001\u6247\u5f62\u3001\u65cb\u8f6c\u5143\u7d20）\u7684\u6839\u57fa，\u914d\u5408 QPainterPath \u53ef\u4ee5\u8868\u8fbe\u4efb\u610f\u77e2\u91cf\u5f62\u72b6\u3002<\/li>\n

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              FAQ \u901f\u67e5\u8868<\/h4>\n\n\n\u95ee\u9898\u4e00\u53e5\u8bdd\u7b54\u6848<\/tr>\n\n\n\n\n\n\n\n\n\n\n
              \u753b\u7b14\u5bbd\u5ea6\u4e3a 0 \u662f\u4ec0\u4e48\u610f\u601d？<\/td>\ncosmetic \u7b14，\u6052\u4e3a 1 \u50cf\u7d20，\u4e0d\u968f scale \u53d8\u7c97<\/td>\n<\/tr>\n
              \u60f3\u753b\u900f\u660e\u80cc\u666f\u7684\u7f13\u5b58\u56fe？<\/td>\npm.fill(Qt::transparent)\u00a0\u4e14\u4f7f\u7528\u5e26 alpha \u7684\u683c\u5f0f<\/td>\n<\/tr>\n
              \u753b\u51fa\u6765\u7684\u5706\u6709\u952f\u9f7f？<\/td>\nsetRenderHint(QPainter::Antialiasing, true)<\/td>\n<\/tr>\n
              \u91cd\u7ed8\u95ea\u70c1\u600e\u4e48\u529e？<\/td>\n\u79bb\u5c4f QPixmap \u7ed8\u5236 + paintEvent \u53ea blit<\/td>\n<\/tr>\n
              \u5982\u4f55\u6e05\u7a7a\u753b\u677f？<\/td>\ncanvas.fill(Qt::white)\u00a0\u540e\u00a0update()<\/td>\n<\/tr>\n
              \u540e\u53f0\u7ebf\u7a0b\u80fd\u7ed8\u5236\u5417？<\/td>\n\u53ea\u80fd\u753b QImage，\u753b\u5b8c\u8f6c QPixmap \u4ea4 GUI \u7ebf\u7a0b<\/td>\n<\/tr>\n
              \u6587\u5b57\u5782\u76f4\u4e0d\u5bf9\u9f50？<\/td>\ndrawText(QPoint) \u7684 y \u662f\u57fa\u7ebf；\u5c45\u4e2d\u7528 QRect \u91cd\u8f7d<\/td>\n<\/tr>\n
              \u56fe\u7247\u653e\u5927\u6a21\u7cca？<\/td>\nSmoothPixmapTransform\u00a0\u6e32\u67d3\u63d0\u793a<\/td>\n<\/tr>\n
              \u9ad8 DPI \u4e0b\u6a21\u7cca？<\/td>\nQt6 \u9ed8\u8ba4\u5f00\u542f；Qt5 \u9700 AA_EnableHighDpiScaling<\/td>\n<\/tr>\n
              \u5982\u4f55\u4fdd\u5b58\u7ed8\u5236\u7ed3\u679c？<\/td>\nQImage::save(path)；\u77e2\u91cf\u4fdd\u5b58\u7528 QPicture \u6216\u5bfc\u51fa SVG（QSvgGenerator）<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"excerpt":{"rendered":"

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