Colors [Solved]

[tonyrueb]

Hello, a friend and I are doing a science project it is on the percentage of bacteria growing we grew them in a dish and took a photo of them. We then made the photo so that it is a monochrome photo with black as no bacteria and white as bacteria.

It is very difficult to find a accrete percentage the manual way so we want to use a computer to help us. We decided to use the pixels of the photo.

In visual basic I wrote the fallowing program

opendio.ShowDialog() 'open file
        Label1.Text = opendio.FileName 'print path on label
        Picture.Image = Image.FromFile(opendio.FileName) 'show image in box
        Dim photo As New Bitmap(opendio.FileName) 'save image as varable
 
        Dim count As Integer ' number of white pixels
        Dim y As Integer 'y pixel
        Dim x As Integer 'x pixel
        Dim photomaxX As Integer = photo.Size.Width 'how many pixels on X axes
        Dim photomaxY As Integer = photo.Size.Height 'how many pixels on Y axes
        For y = 0 To photomaxY - 1 'go though the y axis
            For x = 0 To photomaxX - 1 'go though the x axis
                If photo.GetPixel(x, y).Equals(Color.White) Then 'if the pixel color is white
                    count = count + 1 'add one
                End If
            Next
        Next
 
        MsgBox(count / (photomaxX * photomaxY)) ' show percentage in decmal form

the issue is it always comes up as 0% no matter what picture it is. they are monocrome bitmaps that we are using

[Half]

You should tweak the comparison a bit more. I found at least 2 ways to do it but most certainly there are more.

If photo.GetPixel(x, y).ToArgb.Equals(Color.White.ToArgb) Then
                    count = count + 1 'add one
                End If
 
'Or                
                If photo.GetPixel(x, y).R = 255 AndAlso photo.GetPixel(x, y).G = 255 AndAlso photo.GetPixel(x, y).B = 255 Then
                    count = count + 1 'add one
                End If

-----------
EDIT: The Argb value for white is -1, so 'If photo.GetPixel(x, y).ToArgb = -1 Then' not only works but should be faster as well.

[tonyrueb]

thank you very much, i am relitvly new to programing, so can you please explane what the ToArgb command does thank you

[jmcilhinney]

A description of every type and member is at your fingertips in the MSDN library:

http://msdn2.microsoft.com/en-us/lib...or.toargb.aspx

Having said that, there's no need to turn two Colors to ARGB components to compare them. Just compare the two Colors:

If photo.GetPixel(x, y) = Color.White Then

[tonyrueb]

ok thank you for your help! one more question however. i would like to make it so it will turn all the bactera cells (white pixles) to red or blue pixels. i used the photo.setcolor command but it dosent seem to work, im only guessing here.

[Half]

That would be the SetPixel method.

For y = 0 To photomaxY - 1 'go though the y axis
            For x = 0 To photomaxX - 1 'go though the x axis
 
                If photo.GetPixel(x, y).ToArgb = -1 Then
                    photo.SetPixel(x, y, Color.Red)
                End If
            Next
        Next
 
        'reload the changed picture in the picturebox
        Picture.Image = photo

You are changing the picture, but not the image contained in the picture box. That is why you must reload the changed picture in the picturebox again.

ToArgb returns an Integer describing a color. It may seem useless, but if you decide to use a custom color in your programs, there is no way to use it by it's name as it won't have one. There can be 1000s shades of red and to use those, you must be able to address them uniquely. There is more than one way, i.e. you may use a bunch of integers containing the Red, Green and Blue values. To/From Argb uses only one integer describing all the values - I find it easier to work with.

[tonyrueb]

that would be why it dident work i never reloaded it

[Half]

There is most certainly a way to change pixels in a picture loaded in a picturebox but each redrawing will slow down the program. From what I've seen, it is actually desirable to make all the changes behind the scenes and redraw everything in one pass in the end.

[VBDT]

OR just refresh the picture box aftere editing the image

Picture.Refresh()

[tonyrueb]

the progam still dose not work it gives me this error on the line that changes colors:

An unhandled exception of type 'System.Exception' occurred in system.drawing.dll

Additional information: SetPixel is not supported for images with indexed pixel formats.

could this be because the immage is imported as grayscale (we had to change it from monocrome to grayscale becase it picked up all the area outside of the dish, now we just make the area outside a gray color here is the whole program so far, any other tips would also be good

'open file
        opendio.ShowDialog() 'open file
        Label1.Text = opendio.FileName 'print path on label
        Picture.Image = Image.FromFile(opendio.FileName) 'show image in box
        'initalize varables
        Dim photo As New Bitmap(opendio.FileName) 'save image as varable
        Dim white As Integer = Color.White.ToArgb
        Dim totalmesure As Integer 'total amount of area mesuring
        Dim pixel As Integer
        Dim black As Integer = Color.Black.ToArgb
        Dim countwhite As Integer ' number of white pixels
        Dim countgrayb As Integer ' the number of gray and black pixels
        Dim countgray As Integer 'number of gray
        Dim countblack As Integer ' number of black
        Dim totalpix As Integer 'total pixels
        Dim y As Integer 'y pixel
        Dim x As Integer 'x pixel
        Dim photomaxX As Integer = photo.Size.Width 'how many pixels on X axes
        Dim photomaxY As Integer = photo.Size.Height 'how many pixels on Y axes
 
        For y = 0 To photomaxY - 1 'go though the y axis
            For x = 0 To photomaxX - 1 'go though the x axis
                If photo.GetPixel(x, y).ToArgb = white Then 'test for white pixel
                    countwhite = countwhite + 1 'add one
                End If
                ProgressBar1.Maximum = photomaxX * photomaxY
                pixel = pixel + 1 'add one for every pixel tested
                ProgressBar1.Value = pixel 'move bar
 
            Next
        Next
 
        'find gray and black
        For y = 0 To photomaxY - 1 'go though the y axis
            For x = 0 To photomaxX - 1 'go though the x axis
                If photo.GetPixel(x, y).ToArgb <> white Then 'test for non white pixel
 
                    countgrayb = countgrayb + 1 'add one
                End If
                pixel = 0 'reset
                pixel = pixel + 1 'add one for every pixel tested
                ProgressBar1.Value = pixel
 
 
            Next
        Next
        'find black
        For y = 0 To photomaxY - 1 'go though the y axis
            For x = 0 To photomaxX - 1 'go though the x axis
                If photo.GetPixel(x, y).ToArgb = black Then 'test for black pixel
                    countblack = countblack + 1 'add one
                End If
                pixel = 0 'reset
                pixel = pixel + 1 'add one pixle
                ProgressBar1.Value = pixel
 
 
            Next
        Next
 
        For y = 0 To photomaxY - 1 'go though the y axis
            For x = 0 To photomaxX - 1 'go though the x axis
                If photo.GetPixel(x, y).ToArgb = white Then 'test for white pixel
                    photo.SetPixel(x, y, Color.Blue)
                End If
            Next
        Next
        Picture.Image = photo
 
        'calulate data
        countgray = countgrayb - countblack 'finds number of gray pixels
        totalpix = photomaxX * photomaxY 'finds total pixels
        totalmesure = totalpix - countgray 'finds how much pixels are in the area we want to mesure
 
        MsgBox("total bactera pixels: " & countwhite & vbNewLine & _
        "Total null pixles: " & countblack & vbNewLine & _
        "Total Area: " & totalmesure & vbNewLine & _
        "Percent: " & (countwhite / totalmesure) * 100) ' show all data
    End Sub

[Half]

Is this some other format than bmp? Compressions sometimes use pixel indexing to reduce size.

[VBDT]

Try this

Dim img As New Bitmap(opendio.FileName)
        For x As Integer = 0 To img.Size.Width - 1
            For y As Integer = 0 To img.Size.Height - 1
                If img.GetPixel(x, y) = Color.White Then
                    countwhite += 1
                End If
            Next
        Next

to get the white pixel count. Eite**

[tonyrueb]

i know as a fact from past issues that

if img.GetPixel(x, y) = Color.White Then

does not work you must use .equals and even then it dosent register the pixels for some odd reson, but thanks anyways

[VBDT]

Use this function. It works!

'Gets the pixel count of the color
    Private Function GetPixelCount(ByVal img As Bitmap, ByVal col As Color) As Integer
        Dim count As Integer = 0
        For x As Integer = 0 To img.Size.Width - 1
            For y As Integer = 0 To img.Size.Height - 1
                If img.GetPixel(x, y).ToArgb = col.ToArgb Then
                    count += 1
                End If
            Next
        Next
        Return count
    End Function
 
    'Changes the image color to a new color
    Private Function ChangeImageColor(ByVal img As Bitmap, ByVal currentColor As Color, ByVal newColor As Color) As Bitmap
        For x As Integer = 0 To img.Size.Width - 1
            For y As Integer = 0 To img.Size.Height - 1
                If img.GetPixel(x, y).ToArgb = currentColor.ToArgb Then
                    img.SetPixel(x, y, newColor)
                End If
            Next
        Next
        Return img
    End Function

[Half]

Ok I was wrong about the pixel indexing, it is not only about compression. Anywayz, you will have to modify your code slightly as indexed images can't be manipulated easily when raw. The following will create a non pixel indexed copy of the picture. You then use that copy for pixel manipulation. Rename Photo to photo2 but only here:

Dim photo2 As New Bitmap(opendio.FileName)

Then immediately after 'Dim x As Integer 'x pixel' add the following:

Dim photo As New Bitmap(photo2.Width, photo2.Height) ', System.Drawing.Imaging.PixelFormat.Format16bppGrayScale)
        Dim painter As Graphics = Graphics.FromImage(photo)
        painter.DrawImage(photo2, 0, 0)
        'now you have the "unindexed" original picture, its name is photo

Your code should be working now.

[jmcilhinney]

i know as a fact from past issues that

if img.GetPixel(x, y) = Color.White Then

does not work you must use .equals and even then it dosent register the pixels for some odd reson, but thanks anyways

The "=" operator is not defined for the Color type in .NET 1.x. It is in .NET 2.0. Another reason that everyone should be specifying their version when posting.