"Harry" <le****@gmx.net> wrote in message
news:10***************@news.aic.at...
Hello,
I am using a 2-dimensional matrix for image manipulation and recognition.
The x-axes is image.width pixels long and the y-axes image.height.
All fields have a RGB integer value.
To store this value from the image into the matrix I am using the
bitmap.getPixel(x,y) method because manipulating values in the matrix is
much faster than using the bitmap.setPixel(x,y,color) method.
My problem is, that the getPixel function is also very slow.
Is there a way to get the RGB values from the picture more easily?
This is really a question for the dotnet.Framework.Drawing group, but I
might know a way to speed things up; Have you tried using the LockBits( )
function on the bitmaps? It will return a 1 dimensional array of values in
the current bitmap format. The array looks like this (depending on the
bitmap format):
{r,g,b,r,g,b,r,g,b,r,g,b}
By reading the properties of the BitmapData structure, you can determine how
to loop through the structure so you get one pixel each pass (stepping).
Here is some code I was playing with to invert an image (it is hard-coded
for 32bpp ARGB, and will convert your buffer image to this format
[bmpBuffer]):
'-------------------------------8<----------------------------
'// warning: this is not optimised at all!
'
Sub Invert(bmpBuffer as Bitmap)
Dim bts As Drawing.Imaging.BitmapData
Dim b() As Byte
Dim Y, iBDIndex, X As Integer
Dim bmTemp As New Bitmap(bmpBuffer.Width, bmpBuffer.Height, _
Drawing.Imaging.PixelFormat.Format32bppRgb)
Dim g As Graphics = Graphics.FromImage(bmTemp)
ReDim b((bmpBuffer.Width * 4) * (bmpBuffer.Height))
g.DrawImage(bmpBuffer, 0, 0)
g.Dispose()
bts = bmTemp.LockBits(New Rectangle(0, 0, bmpBuffer.Width, _
bmpBuffer.Height), Drawing.Imaging.ImageLockMode.ReadWrite, _
Drawing.Imaging.PixelFormat.Format32bppArgb)
Runtime.InteropServices.Marshal.Copy(bts.Scan0, b, 0,
((bmpBuffer.Width) * 4) _
* (bmpBuffer.Height))
iBDIndex = 0
'// divides by 4, and steps by 4 because it is ARGB 32bpp
For Y = 0 To (bmpBuffer.Height - 1)
For X = 0 To ((UBound(b) / 4) / (bmpBuffer.Height)) - 1
b(iBDIndex) = Not b(iBDIndex)
b(iBDIndex + 1) = Not b(iBDIndex + 1)
b(iBDIndex + 2) = Not b(iBDIndex + 2)
iBDIndex += 4
Next
Next
Runtime.InteropServices.Marshal.Copy(b, 0, bts.Scan0, _
((bmpBuffer.Width) * 4) * (bmpBuffer.Height))
bmTemp.UnlockBits(bts)
picMain.Image.Dispose()
bmpBuffer.Dispose()
bmpBuffer = New Bitmap(bmTemp)
bmTemp.Dispose()
End Sub
'-------------------------------8<----------------------------
A good site for drawing is
http://www.vbaccelerator.com/ and the Drawing
newsgroup (microsoft.public.dotnet.framework.drawing).
HTH,
Jeremy
