Check if picturebox contains an image - visual-studio

Question

Is there any built-in method of PictureBox compontent to check if a certain portion of its content matches another PictureBox's content? e.g:
I know I can do it by comparing each individual pixel's color with PictureBox's Point(X,Y) Method, but that seems a bit overkill to me. Not to mention it would probably be way too slow.

Answer 1

You can compare each pixel faster by accessing the picture's memory.
It's very easy and fast, I wrote a 2D game engine using this way when I was a new VB6 programmer. My 2D Game Engine (yLib)
All the things you got to do is that get the first pixel's address.
The below function do the job for you:
module1:
Public Declare Function VarPtrArray Lib "msvbvm60" Alias "VarPtr" (Ptr() As Any) As Long
Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pDst As Any, pSrc As Any, ByVal ByteLen As Long)
Public Declare Sub ZeroMemory Lib "kernel32" Alias "RtlZeroMemory" (destination As Any, ByVal Length As Long)
Public Type SAFEARRAYBOUND
cElements As Long
lLbound As Long
End Type
Public Type SAFEARRAY2D
cDims As Integer
fFeatures As Integer
cbElements As Long
cLocks As Long
pvData As Long
Bounds(0 To 1) As SAFEARRAYBOUND
End Type
Public Type BITMAP
bmType As Long
bmWidth As Long
bmHeight As Long
bmWidthBytes As Long
bmPlanes As Integer
bmBitsPixel As Integer
bmBits As Long
End Type
Public Type Picture
pic As STDPicture
c() As Byte
bmp As BITMAP
SA As SAFEARRAY2D
End Type
Public Type lyPicture
pic As STDPicture
c() As Byte
bmp As BITMAP
SA As SAFEARRAY2D
End Type
main form or module:
Private Sub LoadPicArray2D(val As lyPicture)
' get bitmap info from image box
Call GetObjectAPI(val.pic, Len(val.bmp), val.bmp) 'dest
' exit if not 24-bit bitmap
' make the local matrix point to bitmap pixels
If val.bmp.bmPlanes 1 Or val.bmp.bmBitsPixel 24 Or val.bmp.bmWidthBytes / val.bmp.bmWidth 3 Then
Call Err.Raise(500, "Only 24-bit bitmaps.", "Only 24-bit bitmaps.")
End If
With val.SA
.cbElements = 1
.cDims = 2
.Bounds(0).lLbound = 0
.Bounds(0).cElements = val.bmp.bmHeight
.Bounds(1).lLbound = 0
.Bounds(1).cElements = val.bmp.bmWidthBytes
.pvData = val.bmp.bmBits
End With
Call CopyMemory(ByVal VarPtrArray(val.c()), VarPtr(val.SA), 4)
End Sub
Public Sub Main()
Dim pic As lyPicture
Set pic.pic = Form1.TargetPictureBox.Picture
Call LoadPicArray2D(pic)
'Just remember that the picture's memory stored top-down this mean the
' upper pixel lays in lower array bound.
' but the array is correct in horizontal arrangement.
' And the array is formated BGR pic.c(0,0) = B , pic.c(1,0) = G, pic.c(2,0) = R
pic.c(0,0) = 0 ' the pixel at the left bottom (0, MAX_PICTURE_HEIGHT-1) of the picture.
pic.c(0,MAX_PICTURE_HEIGHT-1) = 0 ' the pixel at (0, 0)
' This is very IMPORTANT to release the array at the end of the code.
Call ZeroMemory(ByVal VarPtrArray(val.c()), 4)
' I dont tested this code just copied from my game engine. :D
End Sub