一、坐标系统与坐标变换
坐标系统
qpainter坐标变换相关函数
分组 | 函数原型 | 功能 |
---|---|---|
坐标变换 | void translate(qreal dx,qreal dy) | 坐标系统一定的偏移量,坐标原点平移到新的点 |
void rotate(qreal angle) | 坐标系统顺时针旋转-一个角度 | |
void scale(qreal sx,qreal sy) | 坐标系统缩放 | |
void shear(qrael sh,qreal sy) | 坐标系统做扭转变换 | |
状态保存与恢复 | void save() | 保存painter当前的状态,就是将当前状态压入栈 |
void restore() | 恢复上一次状态,就是从堆栈中弹出上次的状态 | |
void resettransform() | 复位所有的坐标变换 |
示例
绘制五角星
船舰widget窗口,只重载paintevent
函数
#include "widget.h" #include "ui_widget.h" #include <qpalette> #include <qpainter> #include <cmath> widget::widget(qwidget *parent) : qwidget(parent) , ui(new ui::widget) { ui->setupui(this); setpalette(qpalette(qt::white)); setautofillbackground(true); resize(600,300); } widget::~widget() { delete ui; } void widget::paintevent(qpaintevent *event) { q_unused(event); qpainter painter(this); qpen pen; //笔 pen.setstyle(qt::solidline); painter.setpen(pen); painter.setrenderhint(qpainter::antialiasing); //抗锯齿 qbrush brush; //刷子 brush.setcolor(qt::yellow); brush.setstyle(qt::solidpattern); painter.setbrush(brush); //qreal deg = 3.141592*2/5; qreal deg = (360/5)*3.141592/180; qreal r=100; qpoint points[5] = { qpoint(r,0), qpoint(r*std::cos(deg),-r*std::sin(deg)), qpoint(r*std::cos(2*deg),-r*std::sin(2*deg)), qpoint(r*std::cos(3*deg),-r*std::sin(3*deg)), qpoint(r*std::cos(4*deg),-r*std::sin(4*deg)), }; qpainterpath starpath; starpath.moveto(points[3]); starpath.lineto(points[1]); starpath.lineto(points[4]); starpath.lineto(points[2]); starpath.lineto(points[0]); starpath.closesubpath(); qfont font; font.setpointsize(12); starpath.addtext(points[0], font, "0"); starpath.addtext(points[1], font, "1"); starpath.addtext(points[2], font, "2"); starpath.addtext(points[3], font, "3"); starpath.addtext(points[4], font, "4"); painter.setfont(font); painter.save(); //保存 painter.translate(100,120); painter.drawpath(starpath); painter.drawtext(0,0,"s1"); painter.restore(); //恢复 painter.translate(300,120); painter.rotate(90); painter.scale(0.7,0.7); painter.drawpath(starpath); painter.drawtext(0,0,"s2"); painter.resettransform(); painter.translate(500,120); painter.rotate(-90); painter.scale(1.05,1.05); painter.drawpath(starpath); painter.drawtext(0,0,"s3"); }
二、可缩放图形
视口: 绘图设备的任意一个矩形区域的物理坐标,可以只选取物理坐标的一个矩形区域用
于绘图。视口默认情况下等于绘图设备的整个矩形区。
窗口: 对应于视口的矩形区域,只不过是用逻辑坐标定义的坐标系,窗口坐标的中心在矩
形中心。
使用窗口坐标绘制,不用管实际的物理大小
#include "widget.h" #include "ui_widget.h" #include <qpalette> #include <qpainter> #include <qlineargradient> widget::widget(qwidget *parent) : qwidget(parent) , ui(new ui::widget) { ui->setupui(this); setpalette(qpalette(qt::white)); setautofillbackground(true); resize(300,300); } widget::~widget() { delete ui; } void widget::paintevent(qpaintevent *event) { q_unused(event); qpainter painter(this); painter.setrenderhint(qpainter::antialiasing); int w = qwidget::width(); int h = qwidget::height(); int side = qmin(w,h); qrect rect((w-side)/2,(h-side)/2, side,side); //视口大小 painter.drawrect(rect); painter.setviewport(rect); painter.setwindow(-100,-100,200,200); qlineargradient linergradient(0,0,100,0); // 渐变 linergradient.setcolorat(0,qt::yellow); linergradient.setcolorat(1,qt::green); linergradient.setspread(qgradient::padspread); //发散 painter.setcompositionmode(qpainter::rasterop_notsourcexordestination); painter.setbrush(linergradient); for (size_t i=0; i<36; i++) { painter.drawellipse(qpoint(50,0),50,50); painter.rotate(10); } }
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