Introduction
This article demonstrates a very lovely goldfish desktop pet, using alpha-PNG and GD+. This cute goldfish can swim from one side to another of your desktop, and tries to escape when you try to catch it using your mouse.
Background
After I posted these articles: A Cool Vista Sidebar Gadget Style CPUInfo Animate Control! (Fixed)A cool Vista-Sidebar-style clock control (4 style)(fixed)! many people asked me how to make a real alpha-transparent form using these controls. Now, this has become a reality! This is a real alpha-transparent form with animation, even in some none-Vista OSs such as XP!
Have fun! And, do not forget to vote! :)
Using the code
To make a form transparent, use this code to set an alpha-transparent PNG picture as its background:
public void SetBits(Bitmap bitmap)
{
if (!haveHandle) return;
if (!Bitmap.IsCanonicalPixelFormat(bitmap.PixelFormat) ||
!Bitmap.IsAlphaPixelFormat(bitmap.PixelFormat))
throw new ApplicationException("The picture must be " +
"32bit picture with alpha channel");
IntPtr oldBits = IntPtr.Zero;
IntPtr screenDC = Win32.GetDC(IntPtr.Zero);
IntPtr hBitmap = IntPtr.Zero;
IntPtr memDc = Win32.CreateCompatibleDC(screenDC);
try
{
Win32.Point topLoc = new Win32.Point(Left, Top);
Win32.Size bitMapSize = new Win32.Size(bitmap.Width, bitmap.Height);
Win32.BLENDFUNCTION blendFunc = new Win32.BLENDFUNCTION();
Win32.Point srcLoc = new Win32.Point(0, 0);
hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
oldBits = Win32.SelectObject(memDc, hBitmap);
blendFunc.BlendOp = Win32.AC_SRC_OVER;
blendFunc.SourceConstantAlpha = 255;
blendFunc.AlphaFormat = Win32.AC_SRC_ALPHA;
blendFunc.BlendFlags = 0;
Win32.UpdateLayeredWindow(Handle, screenDC, ref topLoc, ref bitMapSize,
memDc, ref srcLoc, 0, ref blendFunc, Win32.ULW_ALPHA);
}
finally
{
if (hBitmap != IntPtr.Zero)
{
Win32.SelectObject(memDc, oldBits);
Win32.DeleteObject(hBitmap);
}
Win32.ReleaseDC(IntPtr.Zero, screenDC);
Win32.DeleteDC(memDc);
}
}
OK, so simple! Now, you can use a timer control to implement the animation function.
Sorry for my poor English! Please see the source code for more details.
Points of Interest
- Developing with GDI+ and C# is a very interesting thing!
- PNG format is very good for drawing alpha pics!
- For more code samples, please visit my personal web site.
History
