修改以下函数void ScanLine::DDALine(QPainter* painter) { int x0=30,y0=10,x1=10,y1=30,x; float dy,dx,k,y; dx=x1-x0; dy=y1-y0; y=y0; k=dy/dx; for(x=x0;x<=x1;x++) { painter->drawPoint(x,int(y+0.5)); y+=k; } painter->drawLine(x0,y0,x1,y1); }使其能被if(menunum==1)//微分绘线 { line=new ScanLine(); // line->DDALine(&painter); update(); }调用
时间: 2023-12-01 09:04:24 浏览: 40
好的,我可以帮您修改这个函数,以便能够在if语句中调用。以下是修改后的代码:
```cpp
void ScanLine::DDALine(QPainter* painter, int x0, int y0, int x1, int y1)
{
int x;
float dy, dx, k, y;
dx = x1 - x0;
dy = y1 - y0;
y = y0;
k = dy / dx;
for (x = x0; x <= x1; x++)
{
painter->drawPoint(x, int(y + 0.5));
y += k;
}
painter->drawLine(x0, y0, x1, y1);
}
```
我们将参数移到函数中,并将DDALine函数的调用方式更改为传递这些参数。现在,在if语句中调用该函数时,我们可以将直线的坐标作为参数传递。例如,要在if语句中绘制从(30, 10)到(10, 30)的直线,您可以这样调用:
```cpp
if (menunum == 1) //微分绘线
{
line = new ScanLine();
line->DDALine(&painter, 30, 10, 10, 30);
update();
}
```
这将创建一个ScanLine对象,然后调用DDALine函数来绘制直线,并使用传递的参数(30, 10, 10, 30)。最后,我们使用update函数来更新窗口。
相关问题
ScanLine::ScanLine() {void ScanLine::DDALine(QPainter *painter) { } }QT报错scanline.cpp:5:5: error: function definition is not allowed here 的解决办法
根据您提供的代码,可以看出ScanLine类的构造函数和DDALine函数定义写在了同一个函数体中,这是不合法的语法,应该将它们分别写在ScanLine类的定义和实现文件中。下面是一个修正后的示例:
ScanLine.h:
```c++
#ifndef SCANLINE_H
#define SCANLINE_H
#include <QPainter>
class ScanLine
{
public:
ScanLine();
void DDALine(QPainter* painter);
void MidLine(QPainter* painter);
void Bresenham(QPainter* painter);
};
#endif // SCANLINE_H
```
ScanLine.cpp:
```c++
#include "ScanLine.h"
ScanLine::ScanLine()
{
// 构造函数的代码
}
void ScanLine::DDALine(QPainter* painter)
{
// 绘制直线的代码
}
void ScanLine::MidLine(QPainter* painter)
{
// 绘制直线的代码
}
void ScanLine::Bresenham(QPainter* painter)
{
// 绘制直线的代码
}
```
需要注意的是,为了在主窗口的paintEvent事件中调用ScanLine类的方法,您需要在ScanLine类的函数定义中将QPainter指针作为参数传递进来。例如:
```c++
void ScanLine::DDALine(QPainter* painter)
{
painter->drawLine(QPointF(0, 0), QPointF(100, 100));
}
```
这样,在主窗口中调用ScanLine类的方法时,就可以将QPainter指针作为参数传递进去:
```c++
void MainWindow::paintEvent(QPaintEvent *event)
{
QPainter painter(this);
if (menunum == 1)
{
ScanLine line;
line.DDALine(&painter);
}
else if (menunum == 2)
{
ScanLine line;
line.MidLine(&painter);
}
else if (menunum == 3)
{
ScanLine line;
line.Bresenham(&painter);
}
}
```
希望这能帮助您解决问题。
#include"scanline.h" #include"qpainter.h" #include<QDebug> #include "mainwindow.h" #include "ui_mainwindow.h" ScanLine::ScanLine() { } void ScanLine::DDALine(QPainter* painter,int x0,int y0,int x1,int y1) { int x; float dy,dx,k,y; dx=x1-x0; dy=y1-y0; y=y0; k=dy/dx; for(x=x0;x<=x1;x++) { painter->drawPoint(x,int(y+0.5)); y+=k; } painter->drawLine(x0,y0,x1,y1); }以上函数无法被 MainWindow::~MainWindow() { delete ui; } void MainWindow::paintEvent(QPaintEvent *event) { Q_UNUSED(event); QPainter painter(this); // // 反走样 painter.setRenderHint(QPainter::Antialiasing, true); // // 设置画笔颜色 painter.setPen(QColor(0, 160, 230)); // // 绘制直线 //// painter.drawLine(QPointF(ScanLine())); if(menunum==1)//微分绘线 { line=new ScanLine(); line->DDALine(&painter, 30, 10, 10, 30); update(); }调用的解决办法
首先,需要修改ScanLine类的DDALine函数的返回值,让它返回一个QPointF类型的值,表示绘制直线的起点和终点坐标。修改后的代码如下:
```cpp
#include "scanline.h"
#include <QPointF>
ScanLine::ScanLine() {}
QPointF ScanLine::DDALine(int x0, int y0, int x1, int y1) {
int x;
float dy, dx, k, y;
dx = x1 - x0;
dy = y1 - y0;
y = y0;
k = dy / dx;
for (x = x0; x <= x1; x++) {
y += k;
}
return QPointF(x0, y0) + QPointF(dx, dy);
}
```
然后在MainWindow的paintEvent函数中,调用DDALine函数获取绘制直线的起点和终点坐标,再使用QPainter的drawLine函数进行绘制。修改后的代码如下:
```cpp
void MainWindow::paintEvent(QPaintEvent *event) {
Q_UNUSED(event);
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing, true);
painter.setPen(QColor(0, 160, 230));
if (menunum == 1) {
line = new ScanLine();
QPointF end = line->DDALine(30, 10, 10, 30);
painter.drawLine(QPointF(30, 10), end);
update();
}
}
```
最后,在MainWindow的析构函数中,需要释放line对象的内存,修改后的代码如下:
```cpp
MainWindow::~MainWindow() {
delete ui;
if (line != nullptr) {
delete line;
}
}
```