Comments on: Alpha Blended Splash Screen in Delphi - Part 1

By: z666zz666z

z666zz666z — Thu, 07 Jul 2011 08:42:23 +0000

Thanks, but i am searching for a TPanel or TLabel that has such alphablend.
I mean: A non transparent form and over it some Panels, one of them must let show what is under it.
For example: A Tipical Panel with "drawing in progress…" over the long time taking drawing proccess on the TForm.Canvas… so while the graphic is been painting the TPanel is shown, but lets see though it the TForm canvas.
Imagine you have a very long process that creates a curve on the TForm.Canvas… while drawing it you need to make Visible a TPanel, but you want to see what is under it with some alphablend, not opaque, not transparent.
So i need a way to add something like AlphaBlend properties of a TForm to a TPanel.
Hope it can be understand.

By: taz

taz — Tue, 22 Mar 2011 00:39:04 +0000

thanks

By: Thunder

Thunder — Fri, 19 Nov 2010 17:46:16 +0000

After some time of researching, I finally have found a way to place child controls on layered windows. Thanks to this code of Jerry.Wang, I have reached my goal. You can read his article on codeproject.com for better understanding, but anyway, the whole point is this.

[edit: Excessive quote snipped]

Sorry for such a big comment, but I think this may be of help to someone as it was to me.
One more time, thanks Anders, for such a great paper, it is worthy of reading, thanks, bye.

By: Fredrik Vestin

Fredrik Vestin — Wed, 17 Nov 2010 07:15:05 +0000

Thanks Anders,
I got it to work now. I must have messed it up when editing the image in Paint.NET.

By: Anders Melander

Anders Melander — Tue, 16 Nov 2010 20:30:42 +0000

Create a new empty form and set Color = clFuchsia, TransparentColor = True and TransparentColorValue = clFuchsia.
Place a TImage control on the form and set Align = alClient and Stretch = True.
Load a transparent PNG into the TImage.
Run.

Be aware that any semi-transparent pixels in the PNG will appear as blended onto clFuchsia, so you need to make sure that all PNG pixels are either 100% opaque or 100% transparent.

By: Fredrik Vestin

Fredrik Vestin — Tue, 16 Nov 2010 18:39:09 +0000

Really? I had a test project that used a BMP that worked fine. I opened the BMP and re-saved it as PNG in Paint.NET and loaded that into the TImage. The clFuchsia color appeared then. Have you done any other steps?

By: Anders Melander

Anders Melander — Tue, 16 Nov 2010 15:24:27 +0000

I just tried it with a PNG in Delphi XE. It worked fine.

By: Fredrik Vestin

Fredrik Vestin — Tue, 16 Nov 2010 15:04:51 +0000

Anders,

Of course, but I expect that many that just want a transparent form will read this article (as I did). It is not obvious that using transparentcolor does work with BMP but not with PNG (no alpha transparency used). This must be considered to be a bug in the VCL.

By: Anders Melander

Anders Melander — Tue, 16 Nov 2010 14:54:37 +0000

Um… The whole point of this article is that the output is transparent and alpha blended.
The TForm.TransparentColor method, which I mentioned above in the section "Different Kinds of Transparency, Color Key transparency", does not support alpha blending.

By: Fredrik Vestin

Fredrik Vestin — Tue, 16 Nov 2010 14:41:25 +0000

Depending on what you need there are easier ways to get a transparent form.

1. Drop a TImage and load a bitmap BMP. The parts of the image that should be transparent should have a specific color e.g. clFuchsia.
2. Set the TImages Transparent property to True.
3 Set the Forms TransparentColor property to True, the TransparentColorValue to clFuchsia and the Color property to clFuchsia.
4. Set the Position, BorderStyle etc. properties on the form as you please.

If the TImage covers the entire form there's no need to set the forms color property. This does not seem to work with PNG images regardless if they are alpha-channel transparent or if they use a specific transparent color like clFuchsia so as far as I can tell your only option is to use BMPs.