GdiPlus[13]: IGPLinearGradientBrush 之多色渐变

多色渐变需要: 一个 "颜色数组" 和一个 "位置数组" (0-1 之间的位置比例);

IGPLinearGradientBrush.InterpolationColors 属性对应一个 IGPColorBlend 对象, 此对象专门用于装载上面两个数组.

IGPColorBlend 的 Colors 和 Positions 两个属性分别对应这两个数组.

下面的三个示例的结果都是一样的.

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测试效果图:

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测试一, 使用开放数组参数构建 IGPColorBlend

---

uses GdiPlus;



procedure TForm1.FormPaint(Sender: TObject);

const

  C1 = $FF000000;

  C2 = $FFFF0000;

  C3 = $FFFFFF00;

  C4 = $FFFF0000;

  C5 = $FF000000;

var

  Graphics: IGPGraphics;

  Rect: TGPRect;

  Brush: IGPLinearGradientBrush;

  ColorBlend: IGPColorBlend;

begin

  Graphics := TGPGraphics.Create(Canvas.Handle);

  Rect.Initialize(ClientRect);

  Brush := TGPLinearGradientBrush.Create(Rect, 0, 0, 0);



  ColorBlend := TGPColorBlend.Create([C1, C2, C3, C4, C5], [0, 0.25, 0.5, 0.75, 1]);

  Brush.InterpolationColors := ColorBlend;



  Graphics.FillRectangle(Brush, Rect);

end;



procedure TForm1.FormResize(Sender: TObject);

begin

  Repaint;

end;


 
   

测试二, 使用静态数组参数构建 IGPColorBlend:

---

uses GdiPlus;



procedure TForm1.FormPaint(Sender: TObject);

var

  Graphics: IGPGraphics;

  Rect: TGPRect;

  Brush: IGPLinearGradientBrush;

  ColorBlend: IGPColorBlend;

  cs: array[0..4] of TGPColor;

  ps: array[0..4] of Single;

begin

  Graphics := TGPGraphics.Create(Canvas.Handle);

  Rect.Initialize(ClientRect);

  Brush := TGPLinearGradientBrush.Create(Rect, 0, 0, 0);



  cs[0] := $FF000000;

  cs[1] := $FFFF0000;

  cs[2] := $FFFFFF00;

  cs[3] := $FFFF0000;

  cs[4] := $FF000000;



  ps[0] := 0;

  ps[1] := 0.25;

  ps[2] := 0.5;

  ps[3] := 0.75;

  ps[4] := 1;



  ColorBlend := TGPColorBlend.Create(cs, ps);

  Brush.InterpolationColors := ColorBlend;



  Graphics.FillRectangle(Brush, Rect);

end;



procedure TForm1.FormResize(Sender: TObject);

begin

  Repaint;

end;


 
   

测试三, 使用数组常量或动态数组参数构建 IGPColorBlend:

---

uses GdiPlus;



procedure TForm1.FormPaint(Sender: TObject);

const

  ps: array[0..4] of Single = (0, 0.25, 0.5, 0.75, 1);

var

  Graphics: IGPGraphics;

  Rect: TGPRect;

  Brush: IGPLinearGradientBrush;

  ColorBlend: IGPColorBlend;

  cs: array of TGPColor;

begin

  Graphics := TGPGraphics.Create(Canvas.Handle);

  Rect.Initialize(ClientRect);

  Brush := TGPLinearGradientBrush.Create(Rect, 0, 0, 0);



  SetLength(cs, 5);

  cs[0] := $FF000000;

  cs[1] := $FFFF0000;

  cs[2] := $FFFFFF00;

  cs[3] := $FFFF0000;

  cs[4] := $FF000000;



  ColorBlend := TGPColorBlend.Create(cs, ps);

  Brush.InterpolationColors := ColorBlend;



  Graphics.FillRectangle(Brush, Rect);

end;



procedure TForm1.FormResize(Sender: TObject);

begin

  Repaint;

end;