C#的System.Drawing 命名空間提供了對 GDI+ 基本圖形功能的訪問
重點在於獲取Graphics對象,例如:
Graphics g = panel1.CreateGraphics
事實上CreateGraphics繼承自Control, 即基本每一種控件都有這個方法
Control.CreateGraphics
在pannel、form上畫圖都一樣,這里以pictureBox為例。DrawRectangle函數為例畫矩形,其他形狀不在這里考慮,自己嘗試很簡單
畫圓是畫橢圓,只需g.DrawEllipse后兩個int參數width,height要設置相等,同時前兩個int參數並不是圓心而是左上角的坐標,沒有自帶的circle函數只能自己封裝
回到正題:
網上給的都是MouseDown MouseMove MouseUp Paint事件相關的代碼,非常的簡單。
using System.Drawing; bool bDrawStart = false; Point pointStart = Point.Empty; Point pointContinue = Point.Empty; private void pictureBox1_MouseDown(object sender, MouseEventArgs e) { if (bDrawStart) { bDrawStart = false; } else { bDrawStart = true; pointStart = e.Location; } } private void pictureBox1_MouseMove(object sender, MouseEventArgs e) { if (bDrawStart) { pointContinue = e.Location; Refresh(); } } private void pictureBox1_MouseUp(object sender, MouseEventArgs e) { if (bDrawStart) { dicPoints.Add(pointStart, pointContinue); } bDrawStart = false; } private void pictureBox1_Paint(object sender, PaintEventArgs e) { if (bDrawStart) { //實時的畫矩形 Graphics g = e.Graphics; g.DrawRectangle(pen, pointStart.X, pointStart.Y, pointContinue.X -pointStart.X, pointContinue.Y - pointStart.Y); } pen.Dispose(); }
用完就發現很明顯的問題了,一次只能畫一個圖形
如何才能一次畫多個呢?不少都說的重寫Paint事件,override之類的函數,多麻煩。
試驗修改Paint事件代碼即可,定義一個字典表記錄畫過的矩形(根據對角兩個點確定一個矩形,對應字典表的key, value,不考慮矩形相交重疊之類的情況),如下:
Dictionary<Point, Point> dicPoints = new Dictionary<Point, Point>(); private void pictureBox1_Paint(object sender, PaintEventArgs e) { System.Drawing.Pen pen = new System.Drawing.Pen(Color.LimeGreen); pen.Width = 2; if (bDrawStart) { //實時的畫矩形 Graphics g = e.Graphics; g.DrawRectangle(pen, pointStart.X, pointStart.Y, pointContinue.X - pointStart.X, pointContinue.Y -pointStart.Y); } //實時的畫之前已經畫好的矩形 foreach (var item in dicPoints) { Point p1 = item.Key; Point p2 = item.Value; e.Graphics.DrawRectangle(pen, p1.X, p1.Y, p2.X - p1.X, p2.Y - p1.Y); } pen.Dispose(); }