Draw-a-gradient-with-alpha-channel


            Title: draw a gradient with alpha channel?
{ .... }
interface
{ .... }
type
 TTriVertex = packed record
 x: Longint;
 y: Longint;
 Red: Word;
 Green: Word;
 Blue: Word;
 Alpha: Word;
 end;
 TGradientFillProc = function(DC: HDC; Verteces: Pointer; NumVerteces: DWORD;
 Meshes: Pointer; NumMeshes: DWORD; Mode: DWORD): DWORD; stdcall;
 
{ .... }
 
var
 MSImg32Lib: THandle;
 GradientFillProc: TGradientFillProc;
 
{ .... }
// Example:
// Beispiel:
procedure TForm1.Button1Click(Sender: TObject);
var
 cr: Cardinal;
 Verteces: array[0..1] of TTriVertex;
 GradientRect: TGradientRect;
begin
 Verteces[0].x := 0;
 Verteces[0].y := 0;
 cr := GetSysColor(COLOR_ACTIVECAPTION);
 Verteces[0].Red := ((cr and $0F0F) or 8);
 Verteces[0].Green := (cr and $0ff00);
 Verteces[0].Blue := ((cr and $0ff0000) or 8);
 Verteces[0].Alpha := 0;
 Verteces[1].x := Width;
 Verteces[1].y := Height;
 cr := GetSysColor(COLOR_GRADIENTACTIVECAPTION);
 Verteces[1].Red := ((cr and $0FF) or 8);
 Verteces[1].Green := (cr and $0ff00);
 Verteces[1].Blue := ((cr and $0ff0000) or 8);
 Verteces[1].Alpha := 0;
 GradientRect.UpperLeft := 0;
 GradientRect.LowerRight := 1;
 GradientFillProc(Canvas.Handle, @Verteces[0], 2, @GradientRect, 1, GRADIENT_FILL_RECT_H);
end;
{ .... }
initialization
 GradientFillProc := nil;
 MSImg32Lib := LoadLibrary('msimg32.dll');
 if MSImg32Lib 0 then
 begin
 GradientFillProc := GetProcAddress(MSImg32Lib, 'GradientFill');
 if @GradientFillProc = nil then
 begin
 FreeLibrary(MSImg32Lib);
 MSImg32Lib := 0;
 end;
 end
 else
 ShowMessage('Could not load DLL');
finalization
 if @GradientFillProc nil then
 GradientFillProc := nil;
 if MSImg32Lib 0 then
 begin
 FreeLibrary(MSImg32Lib);
 MSImg32Lib := 0;
 end;
end.
Graphic Delphi
