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UnityMan
Asked:2020-06-26 05:17:07 +0000 UTC2020-06-26 05:17:07 +0000 UTC

Delphi 7 上的 DrawCurve (GDI+)

  • 772

我正在尝试DrawCurve从 GDIPOBJ.pas 文件中调用一个函数。代码片段：

uses
  ..., GDIPAPI, GDIPOBJ;
...
const Points: array [0..3] of TGPPointF = (
    (X:  30.67; Y: 0),
    (X:  70.68; Y:  30),
    (X: 100.5; Y:  70),
    (X: 290.8; Y:  110));
var
  Pen: TGPPen;
  IGPG:  TGPGraphics;
begin
  IGPG := TGPGraphics.Create(Handle);
  Pen := TGPPen.Create(clBlue,2);

  IGPG.DrawCurve(Pen, Points, 4);  //  !!!!! [Error] There is no overloaded version of 'DrawCurve' that can be called with these arguments !!!!!
end;

我们看一下GDIPOBJ.pas文件中对DrawCurve的描述：

function TGPGraphics.DrawCurve(pen: TGPPen; points: PGPPointF; count: Integer): TStatus;
  begin
    result := SetStatus(GdipDrawCurve(nativeGraphics,
                           pen.nativePen, points,
                           count));
  end;

在上面的函数中，我设置了 TGPPen (Pen), PGPPointF (Points), Integer (4)。怎么了？

我也试过直接通过API函数执行：

GdipDrawCurve(IGPG, Pen, Points, 4);

它对第三个参数发誓：

不兼容的类型：“Array”和“PGPPointF”

但是 Points 数组实际上由 PGPPointF 组成......

delphi-7

1 个回答

  1. Best Answer

    你需要一个指针：

      PGPPointF(@Points[0])

    更多错误 - TGPGraphics 要求您使用窗口（画布）的图形上下文句柄，而不是窗口本身，并且您需要为笔指定不透明度（高字节）。完整的工作示例：

    const Points: array [0..3] of TGPPointF = (
    (X:  30.67; Y: 0),
    (X:  70.68; Y:  30),
    (X: 100.5; Y:  70),
    (X: 290.8; Y:  110));
var
  Pen: TGPPen;
  IGPG:  TGPGraphics;
begin
  IGPG := TGPGraphics.Create(Canvas.Handle);
  Pen := TGPPen.Create($ff0000ff);
  try
    IGPG.DrawCurve(Pen, PGPPointF(@Points), 4);
  finally
    Pen.Free;
    IGPG.Free;
  end;
    • 3

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