我借用了一些代码在图像上绘制一个矩形,例如就像一个选择框。现在,每次单击并拖动鼠标时,代码都会绘制一个矩形。如果仅单击鼠标左键而不拖动,则什么也没有发生-现有的矩形保持不变。如果单击并拖动一个新矩形,则旧矩形将消失。
这几乎与我想要的完全一样(我不想永久在图像上绘制……但是...),但有一个变化:我想单击一下以使矩形消失也是
代码如下:
public partial class ScreenSelection : Form
{
private Point RectStartPoint;
private Rectangle Rect = new Rectangle();
private Brush selectionBrush = new SolidBrush(Color.FromArgb(128, 72, 145, 220));
public ScreenSelection(DataTable buttonData)
{
InitializeComponent();
}
private void Canvas_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
RectStartPoint = e.Location;
Invalidate();
}
}
private void Canvas_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left)
return;
Point tempEndPoint = e.Location;
Rect.Location = new Point(
Math.Min(RectStartPoint.X, tempEndPoint.X),
Math.Min(RectStartPoint.Y, tempEndPoint.Y));
Rect.Size = new Size(
Math.Abs(RectStartPoint.X - tempEndPoint.X),
Math.Abs(RectStartPoint.Y - tempEndPoint.Y));
Canvas.Invalidate();
}
private void Canvas_Paint(object sender, PaintEventArgs e)
{
// Draw the rectangle...
if (Canvas.Image != null)
{
if (Rect != null && Rect.Width > 0 && Rect.Height > 0)
{
e.Graphics.FillRectangle(selectionBrush, Rect);
}
}
}
}
我还让用户加载一个位图作为画布的图像,所以一旦用户这样做,canvas.image将不等于null。
那么如何使该矩形在单击鼠标左键时消失?我已经在左键单击上执行了无效操作,这显然并没有消除它。
我尝试通过以下方式强制在左键单击上设置矩形大小:
if (e.Button == MouseButtons.Left)
{
RectStartPoint = e.Location;
Rect.Height = 0;
Rect.Width = 0;
Invalidate();
}
并尝试了Rect.Size,Rect = Rectangle.Empty,Canvas.Refresh()...
我该怎么做?
编辑: 我也尝试过保存图形状态并恢复它。那是行不通的...(没有错误,只是没有摆脱矩形)
答案 0 :(得分:0)
最后找到了一种方法,可以将绘图保留在paint事件中以提高性能/消除闪烁...
这与fillRectangle s
有关这是工作代码:
public partial class ScreenSelection : Form
{
private Point RectStartPoint;
private Rectangle Rect = new Rectangle();
private Brush selectionBrush = new SolidBrush(Color.FromArgb(128, 72, 145, 220));
private List<Rectangle> Rects = new List<Rectangle>();
private bool RectStart = false;
public ScreenSelection(DataTable buttonData)
{
InitializeComponent();
}
private void Canvas_MouseUp(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
if (RectStartPoint == e.Location)
{
int i = Rects.Count;
if (i > 0) { Rects.RemoveAt(i - 1); }
Canvas.Refresh();
}
}
}
private void Canvas_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
RectStartPoint = e.Location;
int i = Rects.Count;
if (i >= 1) { Rects.RemoveAt(i - 1); }
RectStart = false;
Canvas.Refresh();
}
}
private void Canvas_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left)
return;
Point tempEndPoint = e.Location;
Rect.Location = new Point(
Math.Min(RectStartPoint.X, tempEndPoint.X),
Math.Min(RectStartPoint.Y, tempEndPoint.Y));
Rect.Size = new Size(
Math.Abs(RectStartPoint.X - tempEndPoint.X),
Math.Abs(RectStartPoint.Y - tempEndPoint.Y));
if (!RectStart)
{
Rects.Add(Rect);
RectStart = true;
}
else
{
Rects[(Rects.Count - 1)] = Rect;
}
Canvas.Invalidate();
}
private void Canvas_Paint(object sender, PaintEventArgs e)
{
// Draw the rectangle...
if (Canvas.Image != null)
{
if (Rects.Count > 0)
{
e.Graphics.FillRectangles(selectionBrush, Rects.ToArray());
}
}
}
}
这样做的好处是,如果我小心的话,我还可以在删除其他矩形的同时使某些矩形永久化。