Drawing a bitmap from an array - FAST

[Tor Henrik Hovi]

I recive an array of bytes from a USB 2.0 device.

The array is a 800x600 grayscale picture.

The array is named Buffer

I use this code to present the image:

 

Private Sub BuildImage()

Dim Gray As Byte

Dim c, x, y As Integer

c=0

For y = 0 To 599

For x = 0 To 799

Gray = Buffer©

VideoBitmap.SetPixel(x, y, Color.FromArgb(Gray, Gray, Gray))

c = c + 1

Next

Next

End Sub

 

I takes about .5 sec to complete this on my PC. Wich gives me a frame rate of 2 pictures per sec.

 

I'm looking for a faster way of displaying the picture.

Probably setpixel is not the fastest way?

As you see I have to make a RGB code for the grayscale Color.FromArgb(Gray, Gray, Gray).

Is there some way of inserting the grayscale values directly?

 

Thanx in advance

:D

[divil]

You might want to check out the various constructors for the Bitmap class. One of them accepts a pointer to raw data as one of its parameters, and would certainly be the best way of doing what you're trying to do, if you can get it working.

[Menge]

i agree with divil on the solution.

 

all u need is a pointer to the array start. and then it goes smooth from there... with framerates about 10fps i think

[Tor Henrik Hovi]

OK guys!

 

Thanx allot for your answers, butI could not make it work.

So to test this I created a new form, slapped on a PictureBox and wrote this code:

 

   Dim Buffer As Byte()
   Dim VideoBitmap As Bitmap

   Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
       Dim x, y, c As Integer
       ReDim Buffer(480000)
       c = 1
       For y = 1 To 600
           For x = 1 To 800
               Buffer(c) = CByte(255 / 800 * x)
               c = c + 1
           Next
       Next
   End Sub

   Private Sub PictureBox1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PictureBox1.Click
       Dim BufferPointer As IntPtr
       Dim Stride As Integer
       BufferPointer = Nothing 'How do I get a pointer ro an Array?
       Stride = 800 * 8        'What is Stride??
       VideoBitmap = New Bitmap(800, 600, Stride, Drawing.Imaging.PixelFormat.Format8bppIndexed, BufferPointer)
       VideoBitmap.MakeTransparent()
       PictureBox1.Refresh()
   End Sub

   Private Sub PictureBox1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
       e.Graphics.DrawImage(VideoBitmap, 0, 0, PictureBox.Width, PictureBox.Height)
   End Sub

 

Now I've got a few moe questions;

How do I get a pointer to my Array (Buffer)?

What is Stride??

(The memory size of a row in the stream of pixel data???)

(I just took the number of pixels in a row and multiplied with eight since they are byte?? Probably wrong.)

Please take the time to answer my stupid questions

[Menge]

u could try this:

 

on System.Runtime.InteropServices.Marshal
[C#]
public static void Copy(
  byte[] source,
  int startIndex,
  IntPtr destination,
  int length
);

 

it copies an array of bytes to a pointer. dunno if its the best... but...

[pagis]

but its a 2 dim byte array

 

The Marshal.Copy deals with 1 dim byte array.

so how can you load a 2 Dim byte array into a pointer ?

[Menge]

hrm... the image's Stride is the size of a line of the image in Bytes.

(800x600 image at 32bpp = stride of 800pixels * (32bits/8bitsperbyte))

 

hope this helps :)

[dannyres]

Not sure if this would work but you could try it...

 

           Dim memory As New IO.MemoryStream(ByteArray)
           Dim bmp As New Bitmap(memory)
           memory.Close()

[Dark Kai]

Try looking to this

http://www.xtremedotnettalk.com/t74789.html

[predseda]

I have the same problem like Tor Henrik Hovi, I saw Dark Kai's url http://www.xtremedotnettalk.com/t74789.html , it works good but the code is little bit chaotic for me.

I am looking for something easyer. Only redraw the array to the picturebox. That's all.

Please help.

 

Thanks a lot.