reading the color of pixels

[high6]

how would i read the pixels in a picture box and store there colors in a string like

green,black,blue,pink

or something like that or how would i read just the first pixel of a picture i can do the rest.

[si_the_geek]

You can read a pixel by using the Point method of the picturebox, eg:

MsgBox Picture1.Point(1,1)


Note however that this only returns the colour number, it will not return words as you want - you will have to convert the number somehow.

I think I posted an example of a method to do this, so I'll have a little search!

[Bruce Fox]

Posibly by using the GetPixel API:

The GetPixel function retrieves the red, green, blue (RGB) color value of the pixel at the specified coordinates.

VB4-32,5,6
Declare Function GetPixel Lib "gdi32" Alias "GetPixel" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long) As Long

VB.NET
System.Drawing.Bitmap.GetPixel

Operating Systems Supported

Requires Windows NT 3.1 or later; Requires Windows 95 or later


Library

Gdi32


Parameter Information

· hdc
Identifies the device context.

· nXPos
Specifies the logical x-coordinate of the pixel to be examined.

· nYPos
Specifies the logical y-coordinate of the pixel to be examined.


Return Values

If the function succeeds, the return value is an RGB value. If the pixel is outside of the current clipping region, the return value is CLR_INVALID.

[Bruce Fox]

You can read a pixel by using the Point method of the picturebox, eg:

MsgBox Picture1.Point(1,1)

Kewl

[high6]

You can read a pixel by using the Point method of the picturebox, eg:

MsgBox Picture1.Point(1,1)


Note however that this only returns the colour number, it will not return words as you want - you will have to convert the number somehow.

I think I posted an example of a method to do this, so I'll have a little search!

how would i tell wat color it is?

[Bruce Fox]

I'll reverse engineer this.
http://www.vbforums.com/showpost.php...3&postcount=29

[si_the_geek]

I'm sure I've done this before, but couldn't find it - so here it is again!

This works by converting the number you get (a long) into separate R,G,B values, and then 'estimating' what the colour is - as there is such a range of values this is about the best you will be able to do.

Private Function ColourLongToWords(ByVal lColour As Long) As String
'Converts an RGB colour number to a string equivalent
'By Si_the_geek, VBForums
 
    'ensure value is within range for colours
  lColour = lColour And &HFFFFFF
 
    'convert to separate RGB values
Dim iRed As Integer, iGreen As Integer, iBlue As Integer
  iRed = lColour And &HFF
  iGreen = (lColour \ &H100) And &HFF
  iBlue = lColour \ &H10000
 
    '"guess" the colour based on these values
Dim sColourName As String
  Select Case iRed
  Case Is > 170     'lots of red
      Select Case iGreen
      Case Is > 170     'lots of green
          Select Case iBlue  'blue:  lots/medium/little
          Case Is > 170:  sColourName = "White"
          Case Is > 85:   sColourName = "Bright Yellow"
          Case Else:      sColourName = "Yellow"
          End Select
      Case Is > 85      'medium green
          Select Case iBlue  'blue:  lots/medium/little
          Case Is > 170:  sColourName = "Pink"
          Case Is > 85:   sColourName = "Magenta"
          Case Else:      sColourName = "Orange"
          End Select
      Case Else         'little green
          Select Case iBlue  'blue:  lots/medium/little
          Case Is > 170:  sColourName = "Purple"
          Case Is > 85:   sColourName = "Dark Pink"
          Case Else:      sColourName = "Red"
          End Select
      End Select
 
  Case Is > 85      'medium red
      Select Case iGreen
      Case Is > 170     'lots of green
          Select Case iBlue  'blue:  lots/medium/little
          Case Is > 170:  sColourName = "Cyan"
          Case Is > 85:   sColourName = "Green"
          Case Else:      sColourName = "Bright Green"
          End Select
      Case Is > 85      'medium green
          Select Case iBlue  'blue:  lots/medium/little
          Case Is > 170:  sColourName = "Dark Blue"
          Case Is > 85:   sColourName = "Dark Grey"
          Case Else:      sColourName = "Dark Green"
          End Select
      Case Else         'little green
          Select Case iBlue  'blue:  lots/medium/little
          Case Is > 170:  sColourName = "Dark Blue"
          Case Is > 85:   sColourName = "Purple"
          Case Else:      sColourName = "Dark Red"
          End Select
      End Select
 
  Case Else         'little red
      Select Case iGreen
      Case Is > 170     'lots of green
          Select Case iBlue  'blue:  lots/medium/little
          Case Is > 170:  sColourName = "Cyan"
          Case Is > 85:   sColourName = "Green"
          Case Else:      sColourName = "Bright Green"
          End Select
      Case Is > 85      'medium green
          Select Case iBlue  'blue:  lots/medium/little
          Case Is > 170:  sColourName = "Blue"
          Case Is > 85:   sColourName = "Dark Cyan"
          Case Else:      sColourName = "Dark Green"
          End Select
      Case Else         'little green
          Select Case iBlue  'blue:  lots/medium/little
          Case Is > 170:  sColourName = "Bright Blue"
          Case Is > 85:   sColourName = "Dark Blue"
          Case Else:      sColourName = "Black"
          End Select
      End Select
   End Select
 
  ColourLongToWords = sColourName
 
End Function

Note that I may not have chosen colour names that you like, but it is easy enough to change them!

[high6]

also how would i get the pixels by pixels for a picture?

[si_the_geek]

Do you mean read each pixel in a picturebox?

[high6]

Do you mean read each pixel in a picturebox?

well wat im trying to do is make a program to do this

load a picture box
read each pixel from it 1 by 1 by 1 and if the pixel is white it will add a " " to the textbox and if its black it adds a ".". but i cant get the checking the pixels to work

[si_the_geek]

you could have mentioned that before I wrote the Function above!

All you need to do is create two nested loops (one for vertical and one for horizontal), and read each pixel using Point. You can then use a much shorter version of my function (or just use it as-is) to check whether the value is one of the colours you want.

Dim lX as Long, lY as Long
Dim lPixelColour as Long
  With Picture1
     For lX = 1 to .Picture.Width
       For lY = 1 to .Picture.Height
         lPixelColour = .Point(lX,lY)
         Select Case ColourLongToWords(lPixelColour)
         Case "Black"
           'do something
         Case "White
           'do something else
         End Select
       Next lY
     Next lX
  End With

Note that this is untested, I'm not sure if the loops (or the parameters to Point) are correct.

[high6]

you could have mentioned that before I wrote the Function above!

All you need to do is create two nested loops (one for vertical and one for horizontal), and read each pixel using Point. You can then use a much shorter version of my function (or just use it as-is) to check whether the value is one of the colours you want.

Dim lX as Long, lY as Long
Dim lPixelColour as Long
  With Picture1
     For lX = 1 to .Picture.Width
       For lY = 1 to .Picture.Height
         lPixelColour = .Point(lX,lY)
         Select Case ColourLongToWords(lPixelColour)
         Case "Black"
           'do something
         Case "White
           'do something else
         End Select
       Next lY
     Next lX
  End With

Note that this is untested, I'm not sure if the loops (or the parameters to Point) are correct.

wat would i use in ur function to find if its black or white?

[si_the_geek]

Those parts are already there. If you don't understand which parts to remove, it's probably best to leave it as-is.

Note that there were a couple of typo's in the function, which I have now corrected.

[high6]

Those parts are already there. If you don't understand which parts to remove, it's probably best to leave it as-is.

Note that there were a couple of typo's in the function, which I have now corrected.

it didnt work i got an error in the function it was overflow
iGreen = (lColour And &HFFFF) \ &H100

[Bruce Fox]

....how would i read just the first pixel of a picture i can do the rest.

....also how would i get the pixels by pixels for a picture?.

C'mon some effort on your part is required... (Sorry Si)

[si_the_geek]

Minor change, from this:
iGreen = (lColour And &HFFFF) \ &H100

To this:
iGreen = (lColour And &HFF00) Mod &HFF


I have only one thing to say Bruce, and that is:

[high6]

well its late so im going to bed but i tryed and wat happened was it just wrote "." like 20 times across in 4 rows and that isnt wat the picture was can anoyone help?

[si_the_geek]

What code did you try?

[moeur]

The code for green is still wrong. Should be

iGreen = (lColour \ &H100) And &HFF

[moeur]

it just wrote "." like 20 times across in 4 rows and that isnt wat the picture was

This is probably because you need to adjust the thresholds in the function to catch the color you are trying to read. Can you upload a sample picture so we could try it?

[si_the_geek]

The code for green is still wrong. Should be

iGreen = (lColour \ &H100) And &HFF

Indeed - I just checked again and my previous correction worked for several values of Blue, but not all. Now fixed above!