How can I get the RGB color of the pixel at the cursor location using VB.NET?
How can I get the color of a pixel at the location of the cursor? I know how to get the mouses position using MousePosition but I can not figure out how to get the pixel color at that loca开发者_JS百科tion.
A C# version: How do I get the colour of a pixel at X,Y using c# ?
Should be easy to rewrite in VB.NET.
Quick simple very slow but it works.
The idea is to copy the screen to a bitmap which can be done using the GDI+ build into the drawing.graphics object. Then simply read the bitmap that it generates. Get pixel is very slow. The best way it to read the image byte array directly.
Function MakeScreenShot() As Drawing.Bitmap
Dim out As Drawing.Bitmap
'Get the screen Size
Dim bounds As Rectangle = Screen.GetBounds(Point.Empty)
'create the bitmap
out = New Drawing.Bitmap(bounds.Width, bounds.Height)
'create a graphic object to recive the pic
Using gr As Drawing.Graphics = Graphics.FromImage(out)
'Copy the screen using built in API
gr.CopyFromScreen(Point.Empty, Point.Empty, bounds.Size)
End Using
Return out
End Function
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
Dim BM As Drawing.Bitmap = MakeScreenShot()
Dim mouseloc As Point = Cursor.Position
Dim c As Color = BM.GetPixel(mouseloc.X, mouseloc.Y) ' The Slowest way possable to read a color
Debug.Print(c.R & "," & c.G & "," & c.B)
End Sub
Enjoy.
Try this code:
#Region "#include"
Imports System
Imports System.Drawing
Imports System.Runtime.InteropServices
#End Region
Public Class Test
#Region "From Windows API"
<DllImport("user32.dll", SetLastError:=True)> _
Public Shared Function GetWindowDC(ByVal hwnd As IntPtr) As IntPtr
'Do not try to name this method "GetDC" it will say that user32 doesnt have GetDC !!!
End Function
<DllImport("user32.dll", SetLastError:=True)> _
Public Shared Function ReleaseDC(ByVal hwnd As IntPtr, ByVal hdc As IntPtr) As Int32
End Function
<DllImport("gdi32.dll", SetLastError:=True)> _
Public Shared Function GetPixel(ByVal hdc As IntPtr, ByVal nXPos As Integer, ByVal nYPos As Integer) As UInteger
End Function
#End Region
REM --Test--
#Region "Some Functions"
Public Function GetPixelColor(ByVal x As Integer, ByVal y As Integer) As Color
Dim hdc As IntPtr = GetWindowDC(IntPtr.Zero)
Dim pixel As UInteger = GetPixel(hdc, x, y)
Dim color As Color
ReleaseDC(IntPtr.Zero, hdc)
MsgBox(pixel)
color = color.FromArgb(Int(pixel And &HFF), _
Int(pixel And &HFF00) >> 8, _
Int(pixel And &HFF0000) >> 16)
Return color
End Function
#End Region
REM --Test--
#Region "OnClick"
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim mouseloc As Point = Cursor.Position
Me.Label1.BackColor = GetPixelColor(mouseloc.X, mouseloc.Y)
Me.Refresh()
End Sub
#End Region
End Class
You need button (name==Button1) and label (name==Label1). To get color from screen you will need to use Timer.
If you need to rewrite code from C# to VB.NET use this link: http://www.harding.edu/fmccown/vbnet_csharp_comparison.html
Keep it simple, not very optimized but do the job:
Public Class Form1
Declare Auto Function FindWindow Lib "user32" (ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr
Declare Function GetDC Lib "user32" (ByVal hWnd As IntPtr) As IntPtr
Declare Function ReleaseDC Lib "user32" (ByVal hwnd As IntPtr, ByVal hdc As IntPtr) As IntPtr
Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As IntPtr, ByVal X As Int32, ByVal Y As Int32) As Int32
Private Function CheckScreen()
Dim CursorLoc As Point = Cursor.Position
Dim hDC As IntPtr = GetDC(0) '0 = Get the color to any window on screen, not only your app
Try
Dim CursorColor As Integer = GetPixel(hDC, CursorLoc.X, CursorLoc.Y)
Me.Panel1.BackColor = ColorTranslator.FromWin32(CursorColor) 'a simple panel to show the color
Me.Refresh()
Return True
Catch ex As Exception
Return False
Finally
ReleaseDC(0, hDC)
End Try
End Function
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Me.Timer1.Start() 'Timer with a short delay
End Sub
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
CheckScreen()
End Sub
End Class
This is actually harder than you would guess. I would look for some example code that already does it, and copy their technique.
In the end, the algorithm is going to have to perform these operations:
- Get a bitmap of the desktop/window close to the cursor position
- Index into that bitmap with the cursor position and extract the pixel color
It sounds simple, but is not easy.
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