最近工作中需要给一个网络视频会议c++ sdk编写winform客户端 demo,其中的有个功能为电子白板,初步了解下C#绘图相关的基础知识。
由于在绘制连续点组成的曲线时鼠标移动的速度非常快,所以要考虑效率,否则会漏掉很多点,导致曲线不够自然。
绘图使用的组件为 PictureBox ,变量名为 pictureBox_draw。
基本思路是在PictureBox上绘制过程(MouseMove中),在Image上绘制最终结果(MouseUp),最后设置 pictureBox_draw.Image = mDrawedImg
片段代码如下:
private Graphics mCurrentGraph; //PictureBox组件对应的Graphics
private Pen mPen = new Pen(Color.FromArgb(0,0,0), 3); //绘图的画笔
private Image mDrawedImg; //用来保存最终的绘制结果的图片
private Graphics mImgGraph; //mDrawedImg的Graphics
//.........
{
mCurrentGraph = pictureBox_draw.CreateGraphics();
mCurrentGraph.SmoothingMode = SmoothingMode.AntiAlias; //抗锯齿
mDrawedImg = new Bitmap(pictureBox_draw.Width, pictureBox_draw.Height); //初始化为空白图片
mImgGraph = Graphics.FromImage(mDrawedImg);
mImgGraph.SmoothingMode = SmoothingMode.AntiAlias;
}
private PointF mLastPoint;
private List<PointF> mPoints = new List<PointF>();
private void pictureBox_draw_MouseDown(object sender, MouseEventArgs e)
{
mIsDrawing = true;
mLastPoint = new PointF(e.X, e.Y);
if(mType == "Dot")
{
mPoints.Add(mLastPoint);
}
else if(mType == "Line")
{
}
}
private void pictureBox_draw_MouseMove(object sender, MouseEventArgs e)
{
if (mIsDrawing == false)
return;
PointF currentPoint = new PointF(e.X, e.Y);
if(mType == "Dot")
{
mCurrentGraph.DrawLine(mPen, mLastPoint, currentPoint);
mLastPoint = currentPoint;
mPoints.Add(currentPoint);
}
else if(mType == "Line")
{
pictureBox_draw.Refresh();
mCurrentGraph.DrawLine(mPen, mLastPoint, currentPoint);
}
}
private void pictureBox_draw_MouseUp(object sender, MouseEventArgs e)
{
if (mIsDrawing == false)
return;
if (mType == "Dot")
{
mPoints.Add(new PointF(e.X, e.Y));
mImgGraph.DrawLines(mPen, mPoints.ToArray());
mPoints.Clear();
}
else if (mType == "Line")
{
mImgGraph.DrawLine(mPen, mLastPoint, new PointF(e.X, e.Y));
}
mIsDrawing = false;
pictureBox_draw.Image = mDrawedImg; //已经画好的会面作为当前画板的背景
}