小白请教！在矩形图片上画圆！

Question

在矩形图片上，以同一个点（矩形对角线的交点）为圆形，画出多个相同半径差的同心圆！该怎么编程实现。

Answer 1

可以用  TImage 作为画布，在窗体上放个 TImage控件，设置Image为矩形。
绘图代码如下：
procedure TFmMain.btnDrawClick(Sender: TObject);
var
  i,r: integer;
begin
  //绘制矩形
  imgCanvas.Canvas.Pen.Color := clBlack;
  imgCanvas.Canvas.MoveTo(0,0);
  imgCanvas.Canvas.LineTo(imgCanvas.Width-1,0);
  imgCanvas.Canvas.LineTo(imgCanvas.Width-1,imgCanvas.Height-1);
  imgCanvas.Canvas.LineTo(0,imgCanvas.Height-1);
  imgCanvas.Canvas.LineTo(0,0);
  //绘制圆
  r := imgCanvas.Height div 2-2;
  for i:=10 downto 1 do
  begin
    //采用随机色画圆
    imgCanvas.Canvas.Pen.Color := Random($FFFFFF);
    imgCanvas.Canvas.Ellipse(imgCanvas.Width div 2-r,
                             imgCanvas.Height div 2-r,
                             imgCanvas.Width div 2+r,
                             imgCanvas.Height div 2+r);
    r := r-10;
  end;
end;把绘图代码放在定时器里执行，还会有动画效果 

Answer 2

上面代码都给出来了
楼主连Ctrl+C和Ctrl+V都懒得做么？
去CV一下吧，直接运行看效果的

Answer 3

放一个TImage，假设名字叫Image1:
Image1.Picture.LoadFromFile('xxx');
Image1.Canvas.Ellipse(...);