Gradient inkl. Gloweffekt zeichnen

[turboPASCAL]

GradientFill kann auch Transparents.

Zitat von microsoft:

Note that GradientFill does not use the Alpha member of the TRIVERTEX structure. To use GradientFill with transparency, call GradientFill and then call AlphaBlend with the desired values for the alpha channel of each vertex.

Beispiel:

Delphi-Quellcode:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm1 = class(TForm)
    procedure FormPaint(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

var
  bf: _BLENDFUNCTION = (
    BlendOp: AC_SRC_OVER;
    BlendFlags: 0;
    SourceConstantAlpha: 255;
    AlphaFormat: AC_SRC_ALPHA);

type
  TGFillMode = (GRADIENT_FILL_RECT_H, GRADIENT_FILL_RECT_V);

function GradientFill(DC: HDC; pTriVertex: Pointer; dwNumVertex: DWORD;
  pMesh: Pointer; dwNumMesh, dwMode: DWORD): BOOL; stdcall;
  external 'msimg32.dll' name 'GradientFill';  

function GradientFill4c(DC: HDC; fillRect: TRect; Col: array of COLORREF; FillMode: TGFillMode): Boolean;
type
  _TTRIVERTEX = packed record
    X, Y: DWORD;
    Red, Green, Blue, Alpha: Word;
  end;
var
  tv: array[0..3] of _TTRIVERTEX;
  gr: array[0..1] of GRADIENT_RECT;
  i: integer;
begin
  if length(col) = 4 then
  begin
    // fillmode direction
    gr[0].UpperLeft := 0;
    gr[0].LowerRight := 1;
    gr[1].UpperLeft := 2;
    gr[1].LowerRight := 3;

    ZeroMemory(@tv, sizeof(tv));
    // eckpunkte festlegen
    if FillMode = GRADIENT_FILL_RECT_V then
    begin
      tv[0].x := fillRect.Left;
      tv[0].y := fillRect.Top;
      tv[1].x := fillRect.Right;
      tv[1].y := (fillRect.Top + fillRect.Bottom) div 2;

      tv[2].x := fillRect.Left;
      tv[2].y := (fillRect.Top + fillRect.Bottom) div 2;
      tv[3].x := fillRect.Right;
      tv[3].y := fillRect.Bottom;
    end
    else
    begin
      tv[0].x := fillRect.Left;
      tv[0].y := fillRect.Top;
      tv[1].x := (fillRect.Left + fillRect.Right) div 2;
      tv[1].y := fillRect.Bottom;

      tv[2].x := (fillRect.Left + fillRect.Right) div 2;
      tv[2].y := fillRect.Top;
      tv[3].x := fillRect.Right;
      tv[3].y := fillRect.Bottom;
    end;

    for i := 0 to high(Col) do
    begin
      tv[i].Red   := BYTE(col[i]) shl 8;           // get Color's and Byteswap for Color-Word
      tv[i].Green := BYTE(col[i] shr 8) shl 8;
      tv[i].Blue  := BYTE(col[i] shr 16) shl 8;
      tv[i].Alpha := BYTE(col[i] shr 24) shl 8;
    end;

    Result := GradientFill(DC, @tv, length(tv), @gr, length(gr), DWORD(FillMode));
  end
  else
    Result := False;
end;


// Note that GradientFill does not use the Alpha member of the TRIVERTEX structure.
// To use GradientFill with transparency, call GradientFill and then call AlphaBlend
// with the desired values for the alpha channel of each vertex.

function GradientFill4cT(DC: HDC; fillRect: TRect; Col: array of COLORREF; FillMode: TGFillMode; bf: _BLENDFUNCTION): Boolean;
var
  w, h: integer;
  hBmpDC: HDC;
  hBmp: HBITMAP;
begin

  w := fillRect.Right - fillRect.Left;
  h := fillRect.Bottom - fillRect.Top;

  hBmpDC := CreateCompatibleDC(DC);          //todo: Achtung: keine Fehlerprüfung !
  hBmp := CreateBitmap(w, h, 1, 32, nil);
  SelectObject(hBmpDC, hBmp);

  Result := GradientFill4c(hBmpDC, RECT(0, 0, w, h), Col, FillMode);

  with fillRect do
    Result := Result and Windows.AlphaBlend(
      DC,
      Left, Top, Right - Left, Bottom - Top,
      hBmpDC,
      0, 0, w, h,
      bf);

  DeleteObject(hBmp);
  DeleteDC(hBmpDC);
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  pr: TRect;
begin
  pr := RECT(20,20,160,180);
  GradientFill4c(Self.Canvas.Handle, pr, [$000000FF, $008080FF, $000000FF, $000000C8], GRADIENT_FILL_RECT_V);
  OffSetRect(pr, 50, 50);
  GradientFill4c(Self.Canvas.Handle, pr, [$00FFFFFF, $00FFFFFF, $00FFFFFF, $00C00000], GRADIENT_FILL_RECT_H);

  // GradientFill with transparency

  OffSetRect(pr, 50, 50);
  GradientFill4cT(Self.Canvas.Handle, pr,[$FF0000FF, $A08080FF, $B00000FF, $FF0000C8], GRADIENT_FILL_RECT_V, bf);
end;

end.