GdiPlus[12]: IGPLinearGradientBrush 的其他构建方式

第二种构建方式: TGPLinearGradientBrush.Create(矩形, 颜色1, 颜色2, 渐变模式);

第三种构建方式: TGPLinearGradientBrush.Create(矩形, 颜色1, 颜色2, 角度);

第三种构建方式中的 "角度"(X 轴, 顺时针)相当于是对渐变模式的自定义, 下面两段测试代码的结果是一样的.

另外, 第三种构建方式还有一个默认为 False 的 Boolean 参数, 说明指定角度是否受其他变换的影响.

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测试效果图:

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测试一:

---

uses GdiPlus;

procedure TForm1.FormPaint(Sender: TObject);
const
  C1 = $FFFF0000;
  C2 = $FF0000FF;
var
  Graphics: IGPGraphics;
  Rect, RectBrush: TGPRect;
  Brush: IGPLinearGradientBrush;
begin
  Graphics := TGPGraphics.Create(Canvas.Handle);
  Rect.Initialize(10, 10, 200, 150);
  RectBrush.Initialize(Rect.X + Rect.Width div 8,
                       Rect.Y + Rect.Height div 8,
                       Rect.Width div 4,
                       Rect.Height div 4);

  //LinearGradientModeHorizontal 是默认值
  Brush := TGPLinearGradientBrush.Create(RectBrush, C1, C2, LinearGradientModeHorizontal);
  Graphics.FillRectangle(Brush, Rect);

  Graphics.TranslateTransform(0, Rect.Height + Rect.Y);
  Brush := TGPLinearGradientBrush.Create(RectBrush, C1, C2, LinearGradientModeVertical);
  Graphics.FillRectangle(Brush, Rect);

  Graphics.TranslateTransform(Rect.Width + Rect.X, -Graphics.Transform.OffsetY);
  Brush := TGPLinearGradientBrush.Create(RectBrush, C1, C2, LinearGradientModeForwardDiagonal);
  Graphics.FillRectangle(Brush, Rect);

  Graphics.TranslateTransform(0, Rect.Height + Rect.Y);
  Brush := TGPLinearGradientBrush.Create(RectBrush, C1, C2, LinearGradientModeBackwardDiagonal);
  Graphics.FillRectangle(Brush, Rect);
end;

测试二:

---

uses GdiPlus;

procedure TForm1.FormPaint(Sender: TObject);
const
  C1 = $FFFF0000;
  C2 = $FF0000FF;
var
  Graphics: IGPGraphics;
  Rect, RectBrush: TGPRect;
  Brush: IGPLinearGradientBrush;
begin
  Graphics := TGPGraphics.Create(Canvas.Handle);
  Rect.Initialize(10, 10, 200, 150);
  RectBrush.Initialize(Rect.X + Rect.Width div 8,
                       Rect.Y + Rect.Height div 8,
                       Rect.Width div 4,
                       Rect.Height div 4);

  Brush := TGPLinearGradientBrush.Create(RectBrush, C1, C2, 0);
  Graphics.FillRectangle(Brush, Rect);

  Graphics.TranslateTransform(0, Rect.Height + Rect.Y);
  Brush := TGPLinearGradientBrush.Create(RectBrush, C1, C2, 90);
  Graphics.FillRectangle(Brush, Rect);

  Graphics.TranslateTransform(Rect.Width + Rect.X, -Graphics.Transform.OffsetY);
  Brush := TGPLinearGradientBrush.Create(RectBrush, C1, C2, 45);
  Graphics.FillRectangle(Brush, Rect);

  Graphics.TranslateTransform(0, Rect.Height + Rect.Y);
  Brush := TGPLinearGradientBrush.Create(RectBrush, C1, C2, 135);
  Graphics.FillRectangle(Brush, Rect);
end;