[RESOLVED] Help reading pixels

[christos57]

Hi
Thank you for taking the time to read my post

I am very new to vb net so please be gentle with me

I have recently downloaded 2008 express and found it be be very easy to use for the most part now for my problem

I own a low end telescope 5 inch Newtonian and ever time I try to focus it it takes about 3 seconds to stop shaking so I decided to build a focuser with a stepping motor easy then I decided to interface this into my laptop with the aid of vb.net 208 again not to hard so I built an interface that either manually send a pulse to drive the motor 1 step (1.8 degrees) or half step (0.9 degrees)
and an auto mode that with the use of a slide bar I select an amount of steps the motor will drive, the direction of the drive and weather it is full or half steps. Then I added the input from my modified webcam so I can view the image on the same form all not to hard.

Now what I want to do is
1. to view the image
2. select a part of the image
3. check the difference between the 1 pixel and the 4 pixels around it to determine if there is a great variance between then then move onto the next pixel
4. store the greatest variance in a variable
5. move the stepper 1 more step and repeat steps 1 through 4 until the best focus is obtained

any suggestions would be great or ideas on an easier approch

thanks in advance
christos

[TurboBob]

Heres how I do It:

Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms
Public Class Form1
    Dim g As System.Drawing.Graphics
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Me.Show()
        Me.BackgroundImageLayout = System.Windows.Forms.ImageLayout.None
        Me.BackgroundImage = System.Drawing.Image.FromFile("C:\Test.bmp")
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim n As Integer, k As Integer
        Dim brush3 As Brush
        Dim mypix2 As Color
        Dim pic As Bitmap ' 
        Dim g As System.Drawing.Graphics
        g = Me.CreateGraphics
        pic = Me.BackgroundImage ' You Can of course say pic=System.Drawing.Image.FromFile("C:\Test.bmp")
        For n = 0 To 400
            For k = 0 To 400
                mypix2 = pic.GetPixel(n, k) ' The piece of the code relevant to your Needs
                brush3 = New SolidBrush(Color.FromArgb(mypix2.A, mypix2.R, mypix2.G, mypix2.B))
                g.FillRectangle(brush3, 0 + n, 400 + k, 1, 1)
                brush3.Dispose()
            Next k
        Next n
    End Sub
End Class

Put this into a project and place a test picture in "C:\Test.bmp"

Put a Button on the form - the form as big as you can.

This paints a copy of the image for pixel 0,0 to 400,400
onto the form 400 pixels down on the y axis.

This is of course a dumb way to duplicate
a portion of the bitmap but I like to use little snippets like this to figure out how thing work.

The two lines of Code you need are to create the bitmap bject and to use it's getpixel method.

Hope this Helps

[christos57]

WOW Thanks for the ultra quick response Bob
I copied your snippet but had a little error as the bitmap I was using was smaller then the defined area all fixed and it works great just have to nut out the rest


thanks again
Christos

[TurboBob]

No problem - Need any further help just ask

[christos57]

Just a little feed back
it is all complete and works even better than I could of imagined
the telescope has never been in focus this well

thank you again Bob for your help
P.S. I am quite proud of my self with a total 4 days programming experience so far

[HanneSThEGreaT]

That was great TurboBob!

christos57, I'm glad you have got your thread resolved, please just remember to mark your thread as resolved, as outlined here :

http://www.codeguru.com/forum/showthread.php?t=403073

[TurboBob]

Just a little feed back
it is all complete and works even better than I could of imagined
the telescope has never been in focus this well

thank you again Bob for your help
P.S. I am quite proud of my self with a total 4 days programming experience so far

After just 4 Days I was still trying to put a command button on a form !!

Best of Luck

[HanneSThEGreaT]

christos, you're doing much better than what I did after 4 days, so you are actually quite good

After 4 days I had to replace my keyboard twice, and my mouse one time - oh, and I figured out that the book I was using's cover was made of rubber - because it was still in one piece after I have thrown it a million times! LOL!