Drawing reflection of a progressbar control in winforms VB - vb.net

Question

Here is an image of what I am trying to achieve:
As you can see, there is a slight reflection under the progress bar.
I have a custom progress bar that is heavily based on this code:
http://www.codeproject.com/Articles/19309/Vista-Style-Progress-Bar-in-C
Note: My code is in VB.
Problem - I would like to draw a reflection of that progress bar under it so it looks similar to the image I have given above. I have been told that one way to do it is using pixels, which need to be done manually. Is that the only option? Is there any other/easier way to do it?
I appreciate your help.
Thanks!

Answer 1

Are you looking for something like this?
Here is the code:
Dim pgBarReflection As New Bitmap(ProgressBar1.Width, 20)
ProgressBar1.DrawToBitmap(pgBarReflection, ProgressBar1.ClientRectangle)
For x As Integer = 0 To pgBarReflection.Width - 1
For y As Integer = 0 To pgBarReflection.Height - 1
Dim alpha = 255 - 255 * y \ pgBarReflection.Height
Dim clr As Color = pgBarReflection.GetPixel(x, y)
clr = Color.FromArgb(alpha, clr.R, clr.G, clr.B)
pgBarReflection.SetPixel(x, y, clr)
Next y
Next x
Me.CreateGraphics.DrawImage(pgBarReflection, New Point(ProgressBar1.Left, ProgressBar1.Bottom + 10))
If you want greyscale shadow, replace this line
clr = Color.FromArgb(alpha, clr.R, clr.G, clr.B)
with these two:
Dim greyScale As Integer = CInt(clr.R * 0.3 + clr.G * 0.59 + clr.B * 0.11)
clr = Color.FromArgb(alpha, greyScale, greyScale, greyScale)
You will get something like this:
You can play with parameters to make the shadow more realistic.
Solution is based on this article:
Draw an image with gradient alpha (opacity) values in VB.NET

Answer 2

This solution serves more code but is many times faster than GetPixel/SetPixel. It has one overload without any further settings, or you can use it with alpha start and stop value as well as how much you want to "squeeze" the reflection.
The overloaded simple version assume the background color to be that of the parent. Please note that it has no error checking. You will of course need to implement this in production code.
The result will be like this: (a big thanks to Neolisk for going through the extra trouble producing an image from the code)
The is still room for optimizations (working with "squeezed" version only, un-boxing calculations etc.), but I'll leave that as an execise for the user :-)
Private Sub DrawControlReflection(c As Control)
DrawControlReflection(c, c.Parent.BackColor, 1, 0, 1, 7) 'set you defaults here
End Sub
''' <summary>
''' Draws an reflection of a control
''' </summary>
''' <param name="c">The control to make an reflection of</param>
''' <param name="bgCol">Background color in transparent area</param>
''' <param name="startTrans">0.0-1.0, start value of reflection transparency, usually 1</param>
''' <param name="endTrans">0.0-1.0, end value of reflection transparency, usually 0</param>
''' <param name="squeeze">height of reflection, values 0-1, 1=100%, 0.5=50% etc.</param>
''' <param name="delta">y offset of reflection from control's bottom</param>
''' <remarks>
''' Provided AS-IS.
''' Created by Epistmex, use as you want.
''' Need implementation of error checking (bitmap allocations etc.)
''' </remarks>
Private Sub DrawControlReflection(c As Control,
bgCol As Color,
startTrans As Single,
endTrans As Single,
squeeze As Single,
delta As Integer)
'
'-- Original control's bound
'
Dim r As Rectangle = c.ClientRectangle
'
'-- Destination bound
'
Dim rd As Rectangle = New Rectangle(c.Left,
c.Top + r.Height + 1 + delta,
r.Width,
CInt(r.Height * squeeze))
'
'-- Create a bitmap for reflection and copy control content into it
'
Dim bmp As New Bitmap(r.Width,
r.Height,
Imaging.PixelFormat.Format24bppRgb)
c.DrawToBitmap(bmp, r)
'
'-- flip it vertically
'
bmp.RotateFlip(RotateFlipType.RotateNoneFlipY)
'
'-- Add gradient "transparency" to bitmap
'
AddGradientAlpha(bmp, r, startTrans, endTrans, bgCol)
'
'-- Draw the result
'
Dim g As Graphics = c.Parent.CreateGraphics
if squeeze <> 1 Then g.InterpolationMode = _
Drawing2D.InterpolationMode.HighQualityBicubic
g.DrawImage(bmp, rd)
g.Dispose()
bmp.Dispose()
End Sub
Private Sub AddGradientAlpha(ByRef bmp As Bitmap, r As Rectangle, s As Single, e As Single, bc As Color)
Dim bmpLock As Imaging.BitmapData = bmp.LockBits(r, Imaging.ImageLockMode.ReadWrite, Imaging.PixelFormat.Format24bppRgb)
Dim st As Integer = bmpLock.Stride
Dim bytesBmp(bmpLock.Stride * bmp.Height) As Byte
Runtime.InteropServices.Marshal.Copy(bmpLock.Scan0, bytesBmp, 0, bytesBmp.Length)
'
'-- Calculate and create pre-multiplied gradient alpha
'
Dim x, y, dx, l, d As Integer
Dim aDiff As Double = s - e
Dim a As Double
Dim b As Byte
Dim h As Integer = bmp.Height - 1
For y = 0 To h
l = y * st 'line. cache the calculations we can
d = h - y 'position with opposite value
If d = 0 Then
a = e
Else
a = (aDiff * d / h) + e 'gradient value ad 0.5 to h for even more accuracy
End If
If a < 0 Then a = 0
If a > 1 Then a = 1
a = a * a 'power of 2 to make gradient steeper
For x = 0 To bmp.Width - 1
dx = l + x * 3 'x pos in buffer
'make gradient of colors in buffer + mix bg color
bytesBmp(dx) = CByte(bytesBmp(dx) * a + ((1 - a) * bc.B))
bytesBmp(dx + 1) = CByte(bytesBmp(dx + 1) * a + ((1 - a) * bc.G))
bytesBmp(dx + 2) = CByte(bytesBmp(dx + 2) * a + ((1 - a) * bc.R))
Next
Next
'
'-- Marshal back
'
Runtime.InteropServices.Marshal.Copy(bytesBmp, 0, bmpLock.Scan0, bytesBmp.Length)
bmp.UnlockBits(bmpLock)
End Sub