var hDesktop: HWND; DC: HDC; T: BLENDFUNCTION; begin hDesktop := GetDesktopWindow; DC := GetDC(hDesktop); try T.BlendOp := AC_SRC_OVER; T.BlendFlags := 0; T.SourceConstantAlpha := $80; T.AlphaFormat := 0; Image1.Canvas.Brush.Color := clGreen; Image1.Canvas.FillRect(Rect(0, 0, Image1.Width, Image1.Height)); Windows.AlphaBlend(Image1.Canvas.Handle, 0, 0, Image1.Width, Image1.Height, DC, 0, 0, Image1.Width, Image1.Height, T); finally ReleaseDC(hDesktop, DC); end; end;
Friday, April 11, 2008
Draw a translucent effect image
We may use windows GDI function AlphaBlend to draw translucent graphic. The following example extract a portion of desktop image and draw to TImage.canvas with translucent effect. The resulting graphic will looks like there is a green color transparent sheet cover on the image.