做过安防视频监控的同学都清楚，在视频监控系统软件上都可以看到一个云台控制区域，可以对球机进行下下左右等八个方位的运动控制，还可以进行复位，一般都是美工作图好，然后贴图的形式加入到软件中，好处是程序简单，界面美工，主要取决于美工的美图能力，缺点是对于各种分辨率的适应性稍微差点，需要不同的图片切图贴图，除非默认做好的是大图自适应看不出差别，可能大部分人所在的公司都是小公司，一般美工人员比较少甚至没有，都需要程序员一人负责，甚至一开始就要考虑到各种分辨率的应用场景以及后期可能的换肤换色等。
之前做过很多自定义控件，大部分都采用了qpainter的形式绘制，有个好处就是自适应任意分辨率，所以思考着这个云台控制仪表盘也采用纯painter绘制的形式，据说纯painter绘制还可以轻松移植到qml中，这又坚定了我用qpainter绘制的决心。所谓心中有坐标系，万物皆painter。
观察云台仪表盘下来，基本上就这几部分组成，圆形底盘，八个角，中间部分按钮，整个的控件的难点就在于八个角的定位，中间部分很好定位，而且八个角不是绝对的位置，都是相对于界面的宽高按照等比例自适应排列的。八个角的鼠标按下要做出对应的反应，发送出对应型号，网上大部分人都是切图或者放置label或者按钮来贴图实现，绑定事件过滤器过滤鼠标按下然后再发出信号。我这里为了提升逼格，直接采用位置坐标计算法。
核心算法：
void GaugeCloud::paintEvent(QPaintEvent *)
{
int width = this->width();
int height = this->height();
int side = qMin(width, height);
//以中心点为基准,分别计算八方位区域和中间区域
QPointF center = this->rect().center();
double centerSize = (double)side / ((double)100 / 30);
double iconSize = (double)side / ((double)100 / 10);
double offset1 = 3.6;
double offset2 = 2.65;
//中间区域
centerRect = QRectF(center.x() - centerSize / 2, center.y() - centerSize / 2, centerSize, centerSize);
//左侧图标区域
leftRect = QRectF(center.x() - iconSize * offset1, center.y() - iconSize / 2, iconSize, iconSize);
//上侧图标区域
topRect = QRectF(center.x() - iconSize / 2, center.y() - iconSize * offset1, iconSize, iconSize);
//右侧图标区域
rightRect = QRectF(center.x() + iconSize * (offset1 - 1), center.y() - iconSize / 2, iconSize, iconSize);
//下侧图标区域
bottomRect = QRectF(center.x() - iconSize / 2, center.y() + iconSize * (offset1 - 1), iconSize, iconSize);
//左上角图标区域
leftTopRect = QRectF(center.x() - iconSize * offset2, center.y() - iconSize * offset2, iconSize, iconSize);
//右上角图标区域
rightTopRect = QRectF(center.x() + iconSize * (offset2 - 1), center.y() - iconSize * offset2, iconSize, iconSize);
//左下角图标区域
leftBottomRect = QRectF(center.x() - iconSize * offset2, center.y() + iconSize * (offset2 - 1), iconSize, iconSize);
//右下角图标区域
rightBottomRect = QRectF(center.x() + iconSize * (offset2 - 1), center.y() + iconSize * (offset2 - 1), iconSize, iconSize);
//绘制准备工作,启用反锯齿,平移坐标轴中心,等比例缩放
QPainter painter(this);
painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
painter.translate(width / 2, height / 2);
painter.scale(side / 200.0, side / 200.0);
if (cloudStyle == CloudStyle_Black) {
//绘制外圆背景
drawCircle(&painter, 99, bgColor);
//绘制圆弧
drawArc(&painter);
//绘制中间圆盘背景
drawCircle(&painter, 83, baseColor);
//绘制内圆背景
drawCircle(&painter, 40, arcColor);
//绘制内圆边框
drawCircle(&painter, 33, borderColor);
//绘制内圆
drawCircle(&painter, 30, (pressed && centerRect.contains(lastPoint)) ? bgColor : baseColor);
} else if (cloudStyle == CloudStyle_White) {
//绘制外圆背景
drawCircle(&painter, 99, QColor(249, 249, 249));
//设置圆锥渐变
QConicalGradient gradient(0, 0, 100);
gradient.setColorAt(0, QColor(34, 163, 169));
gradient.setColorAt(0.4, QColor(240, 201, 136));
gradient.setColorAt(0.7, QColor(211, 77, 37));
gradient.setColorAt(1, QColor(34, 163, 169));
//绘制彩色外圆
drawCircle(&painter, 90, gradient);
//绘制中间圆盘背景
drawCircle(&painter, 83, QColor(245, 245, 245));
//绘制内圆背景
drawCircle(&painter, 33, QColor(208, 208, 208));
//绘制内圆边框
drawCircle(&painter, 32, QColor(208, 208, 208));
//绘制内圆
drawCircle(&painter, 30, (pressed && centerRect.contains(lastPoint)) ? QColor(255, 255, 255) : QColor(245, 245, 245));
} else if (cloudStyle == CloudStyle_Blue) {
//设置圆锥渐变
QConicalGradient gradient(0, 0, 100);
gradient.setColorAt(0, QColor(34, 163, 169));
gradient.setColorAt(0.4, QColor(240, 201, 136));
gradient.setColorAt(0.7, QColor(211, 77, 37));
gradient.setColorAt(1, QColor(34, 163, 169));
//绘制色彩外圆
drawCircle(&painter, 99, gradient);
//绘制中间圆盘背景
drawCircle(&painter, 91, QColor(31, 66, 98));
//绘制内圆背景
drawCircle(&painter, 33, QColor(23, 54, 81));
//绘制内圆边框
drawCircle(&painter, 30, QColor(150, 150, 150));
//绘制内圆
drawCircle(&painter, 30, (pressed && centerRect.contains(lastPoint)) ? QColor(35, 82, 133) : QColor(34, 73, 115));
} else if (cloudStyle == CloudStyle_Purple) {
//设置圆锥渐变
QConicalGradient gradient(0, 0, 100);
gradient.setColorAt(0, QColor(87, 87, 155));
gradient.setColorAt(0.4, QColor(129, 82, 130));
gradient.setColorAt(0.7, QColor(54, 89, 166));
gradient.setColorAt(1, QColor(87, 87, 155));
//绘制色彩外圆
drawCircle(&painter, 99, gradient);
//绘制中间圆盘背景
drawCircle(&painter, 91, QColor(55, 55, 92));
//绘制内圆背景
drawCircle(&painter, 33, QColor(49, 48, 82));
//绘制内圆边框
drawCircle(&painter, 30, QColor(82, 78, 131));
//绘制内圆
drawCircle(&painter, 30, (pressed && centerRect.contains(lastPoint)) ? QColor(85, 81, 137) : QColor(62, 59, 103));
}
//绘制八方位+中间图标
drawText(&painter);
#if 0
//重置坐标系,并绘制八方位区域及中间区域,判断是否正确
painter.resetMatrix();
painter.resetTransform();
painter.setPen(Qt::white);
painter.drawRect(centerRect);
painter.drawRect(leftRect);
painter.drawRect(topRect);
painter.drawRect(rightRect);
painter.drawRect(bottomRect);
painter.drawRect(leftTopRect);
painter.drawRect(rightTopRect);
painter.drawRect(leftBottomRect);
painter.drawRect(rightBottomRect);
#endif
}
void GaugeCloud::drawCircle(QPainter *painter, int radius, const QBrush &brush)
{
painter->save();
painter->setPen(Qt::NoPen);
painter->setBrush(brush);
//绘制圆
painter->drawEllipse(-radius, -radius, radius * 2, radius * 2);
painter->restore();
}
void GaugeCloud::drawArc(QPainter *painter)
{
int radius = 91;
painter->save();
painter->setBrush(Qt::NoBrush);
QPen pen;
pen.setWidthF(10);
pen.setColor(arcColor);
painter->setPen(pen);
QRectF rect = QRectF(-radius, -radius, radius * 2, radius * 2);
painter->drawArc(rect, 0 * 16, 360 * 16);
painter->restore();
}
void GaugeCloud::drawText(QPainter *painter)
{
bool ok;
int radius = 100;
painter->save();
//判断当前按下坐标是否在中心区域,按下则文本不同颜色
if (pressed && centerRect.contains(lastPoint)) {
emit mousePressed(8);
painter->setPen(pressColor);
} else {
painter->setPen(textColor);
}
QFont font;
font.setPixelSize(25);
#if (QT_VERSION >= QT_VERSION_CHECK(4,8,0))
font.setHintingPreference(QFont::PreferNoHinting);
#endif
painter->setFont(font);
//绘制中间图标
QRectF centerRect(-radius, -radius, radius * 2, radius * 2);
QString centerText = this->centerText.replace("0x", "");
QChar centerChar = QChar(centerText.toInt(&ok, 16));
painter->drawText(centerRect, Qt::AlignCenter, centerChar);
//绘制八方位图标
radius = 70;
int offset = 15;
int steps = 8;
double angleStep = 360.0 / steps;
font.setPixelSize(20);
painter->setFont(font);
//从下侧图标开始绘制,顺时针旋转
QRect iconRect(-offset / 2, radius - offset, offset, offset);
QString iconText = this->iconText.replace("0x", "");
QChar iconChar = QChar(iconText.toInt(&ok, 16));
for (int i = 0; i < steps; i++) {
//判断鼠标按下的是哪个区域
if (pressed) {
bool contains = false;
if (bottomRect.contains(lastPoint) && i == 0) {
contains = true;
} else if (leftBottomRect.contains(lastPoint) && i == 1) {
contains = true;
} else if (leftRect.contains(lastPoint) && i == 2) {
contains = true;
} else if (leftTopRect.contains(lastPoint) && i == 3) {
contains = true;
} else if (topRect.contains(lastPoint) && i == 4) {
contains = true;
} else if (rightTopRect.contains(lastPoint) && i == 5) {
contains = true;
} else if (rightRect.contains(lastPoint) && i == 6) {
contains = true;
} else if (rightBottomRect.contains(lastPoint) && i == 7) {
contains = true;
}
if (contains) {
painter->setPen(pressColor);
emit mousePressed(i);
} else {
painter->setPen(textColor);
}
} else {
painter->setPen(textColor);
}
painter->drawText(iconRect, Qt::AlignCenter, iconChar);
painter->rotate(angleStep);
}
painter->restore();
}