The Windows GUI is standing upon two pillers. Vector Graphics and Bitmap Graphics. Being quite difficult to manage, Vector Graphics are always very painful to handle but the possiblities are nearly impossible to find a limit. Where as Bitmaps are concerned, they are heavy Windows objects ( though DIBs are not ). Since the arrival of electrifying GUIs in the Windows, the interest of programmers towards Image Processing has awfully increased. This article shall tell you how to do it and how to make it work faster.
    There are many ways to do it, according to the requirements of the Image Filter, we are dealing with. A simple method is to use GetPixel and SetPixel API.This method is very slow but better for novice. I still remember 4 years ago when I created my first Image Processor, it used to take 1.5 seconds to Grayscale a picture of 250x250 pixels. But it was obviously the first step towards my new Greyscale function which does the same task on a picture of same dimensions in just 16 milliseconds. So lets see my first Greyscale function.

Option Explicit ' Structures Declaration Private Type RGBQUAD     rgbBlue As Byte     rgbGreen As Byte     rgbRed As Byte     rgbReserved As Byte End Type Private Type BITMAPINFOHEADER   biSize          As Long   biWidth         As Long   biHeight        As Long   biPlanes        As Integer   biBitCount      As Integer   biCompression   As Long   biSizeImage     As Long   biXPelsPerMeter As Long   biYPelsPerMeter As Long   biClrUsed       As Long   biClrImportant  As Long End Type Private Type BITMAPINFO     bmiHeader As BITMAPINFOHEADER     bmiColors As RGBQUAD End Type ' API Declaration Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long) As Long Private Declare Function SetPixelV Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long, ByVal crColor As Long) As Long Private Declare Function GetDIBits Lib "gdi32" (ByVal aHDC As Long, ByVal hBitmap As Long, ByVal nStartScan As Long, _ ByVal nNumScans As Long, lpBits As Any, lpBI As BITMAPINFOHEADER, ByVal wUsage As Long) As Long Private Declare Function SetDIBits Lib "gdi32" (ByVal hdc As Long, ByVal hBitmap As Long, ByVal nStartScan As Long, _ ByVal nNumScans As Long, lpBits As Any, lpBI As BITMAPINFOHEADER, ByVal wUsage As Long) As Long Private Declare Function CreateCompatibleDC Lib "gdi32.dll" (ByVal hdc As Long) As Long Private Declare Function CreateCompatibleBitmap Lib "gdi32" (ByVal hdc As Long, ByVal nWidth As Long, ByVal nHeight As Long) As Long Private Declare Function SelectObject Lib "gdi32.dll" (ByVal hdc As Long, ByVal hObject As Long) As Long Private Declare Function DeleteObject Lib "gdi32.dll" (ByVal hObject As Long) As Long Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal X As Long, ByVal Y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long Private Declare Function GetTickCount Lib "kernel32.dll" () As Long Private Declare Function CreateDIBSection Lib "gdi32.dll" (ByVal hdc As Long, ByRef pBitmapInfo As BITMAPINFO, ByVal un As Long, lplpVoid As Long, ByVal handle As Long, ByVal dw As Long) As Long 'Constants Declaration Private Const SRCCOPY = &HCC0020 Private Const BI_RGB = 0& Private Const DIB_RGB_COLORS = 0 ' Personal Declarations Dim bDIB() As RGBQUAD Dim bih As BITMAPINFOHEADER Dim DC As Long, DIBSection As Long, oldDIB As Long Dim bi As BITMAPINFO Private Sub Grey1_click() Dim ti As Long ti = GetTickCount Dim x As Long, y As Long, Pixel As Long, GrayScale As Long For x = 0 To Picture1.ScaleWidth For y = 0 To Picture1.ScaleHeight         Pixel = GetPixel(Picture1.hdc, x, y) ' Get one pixel from the PictureBox         ' Now we process the acquired pixel         GrayScale = ((77& * (Pixel And &HFF&) + 152& * (Pixel And &HFF00&) \ &H100& + 28& * (Pixel \ &H10000)) \ 256&) * &H10101         ' Then setting back the processed pixel in the PictureBox         Call SetPixelV(Picture1.hdc, x, y, GrayScale) Next y Next x MsgBox "Operation completed in " & GetTickCount - ti & " ms" End Sub

The script above is a simple thing to understand. Nothing more than like getting a single pixel at a time, processing it and then setting it back. But this is is quit slow especially when you talk like a professional practical programmer. Let start coding a faster version of the same filter.

Private Sub Grey2_Click() Dim x As Long, y As Long, TempDC As Long, TempBIT As Long, OldTempBIT As Long, Pixel As Long, GrayScale As Long,ti As Long ti = GetTickCount TempDC = CreateCompatibleDC(Picture1.hdc) ' Creating a Device Handle compatible with the Picturebox TempBIT = CreateCompatibleBitmap(Picture1.hdc, Picture1.ScaleWidth, Picture1.ScaleHeight) ' Creating a DDB compatible with the Picturebox OldTempBIT = SelectObject(TempDC, TempBIT) ' Selecting the compatible DDB in the compatible DC Call BitBlt(TempDC, 0, 0, Picture1.ScaleWidth, Picture1.ScaleHeight, Picture1.hdc, 0, 0, SRCCOPY) ' Copying the contents of Picturebox in the compatible DC For x = 0 To Picture1.ScaleWidth For y = 0 To Picture1.ScaleHeight         Pixel = GetPixel(TempDC, x, y) ' Get one pixel from the Temporary Memory DC         ' Now we process the acquired pixel         GrayScale = ((77& * (Pixel And &HFF&) + 152& * (Pixel And &HFF00&) \ &H100& + 28& * (Pixel \ &H10000)) \ 256&) * &H10101         ' Then setting back the processed pixel in the temporary DC         Call SetPixelV(TempDC, x, y, GrayScale) Next y Next x ' Now copying back the contents of compatible DC to Picturebox Call BitBlt(Picture1.hdc, 0, 0, Picture1.ScaleWidth, Picture1.ScaleHeight, TempDC, 0, 0, SRCCOPY) Call SelectObject(TempDC, OldTempBIT) ' Good Programming Practice Call DeleteObject(TempBIT) ' Deleting the compatible DDB Call DeleteDC(TempDC) ' Deleting the temporary compatible DC MsgBox "Operation completed in " & GetTickCount - ti & " ms" End Sub

By now I suppose you got the backround of what we are trying to do here. Do the Processing as fast as possible, and with lesser memory space being acquired. The above method is the most simplest to do if we are after speed. But in this script we are using DDB which some programmers may deslike. But this really affects the speed because then you are talking in terms of memory, and obviously the calculations on the data that is in memory will be much faster than getting and then setting back the data from the screen itself.

Private Sub Grey3_Click() Dim ti As Long ti = GetTickCount Dim x As Long, y As Long ' Initiallizing the BITMAPINFOHEADER Structure With bih         .biSize = 40         .biPlanes = 1         .biHeight = -Picture1.ScaleHeight         .biWidth = Picture1.ScaleWidth         .biBitCount = 32 End With ' Redifing the limits of our local Pixel Array to the ' dimensions of the Picture in the Picturebox ReDim bDIB(1 To Picture1.ScaleWidth, 1 To Picture1.ScaleHeight) As RGBQUAD ' Finally getting a copy of the whole original ' Pixel Array in our local Pixel Array bDIB() Call GetDIBits(Picture1.hdc, Picture1.Picture.Handle, 0&, Picture1.ScaleHeight, bDIB(1, 1), bih, 0) ' Now we are about to edit each and every pixel in the array For x = 1 To Picture1.ScaleWidth   For y = 1 To Picture1.ScaleHeight         bDIB(x, y).rgbBlue = 0.3 * bDIB(x, y).rgbRed + 0.587 * bDIB(x, y).rgbGreen + 0.114 * bDIB(x, y).rgbBlue         bDIB(x, y).rgbGreen = bDIB(x, y).rgbBlue         bDIB(x, y).rgbRed = bDIB(x, y).rgbBlue   Next y Next x ' The local array is edited. At last we've to copy the ' local array to the Picturebox original array Call SetDIBits(Picture1.hdc, Picture1.Picture.Handle, 0, Picture1.ScaleHeight, bDIB(1, 1), bih, 0) ' You've to refresh the Picturebox regardless the property of AutoRedraw. Picture1.Refresh ' This statement is very neccessary Erase bDIB() MsgBox "Operation completed in " & GetTickCount - ti & " ms" End Sub

This is a simple way to do it. No extra DIBs or DDBs are created. In the frst phase the Pixel Array of the picture allready present in the Picturebox is being copied to a local made array called bDIB(). Then we process this local array and then at last we finally put back the processed Pixel Array to the Picturebox. A simple effective and very fast method to edit the pixels of a picture allready present in any Picturebox. This is a very simple way to achieve speed, and when I say speed I mean it. This function takes 31 milliseconds on my machine(AMD Sempron, 1.20 GHz, 192 MB RAM). But you see the day you relax on the accuracy of your results will be your last day in programming. There is no restriction over trying any other way to get the results in lesser time. And obviously there is no cure for the speed geeks. So I'm putting down another version of the same filter. But remember this is a organizational function which only implies that you must use it when you are dealing with a whole sole Image Processing project. Actually this is the version that I coded in the DIB Section article.

Private Sub Form_Load() ' Creating the HDC to contain the DIB Section DC = CreateCompatibleDC(Picture1.hdc) If (DC <> 0) Then   ' Checking whether the DC is made or not ' Finally making the 6 settings required by the programmer to set With bi.bmiHeader     .biSize = 40     .biWidth = Picture1.ScaleWidth     ' Picture Width     .biHeight = -Picture1.ScaleHeight  ' Picture Height(dont confuse with the (-) sign.Just make it compulsory)     .biPlanes = 1     .biBitCount = 32     .biSizeImage = (((Picture1.ScaleWidth * 3) + 3) And &HFFFFFFFC) * Picture1.ScaleHeight ' This is how we can calculate the Image Size in Bytes End With Dim addr As Long ' This will contain the memory address to the Bitmap data in the memory ' And now making the EMPTY DIB Section with above settings DIBSection = CreateDIBSection(DC, bi, DIB_RGB_COLORS, addr, 0, 0) If (DIBSection <> 0) Then ' Checking whether the DIB Section is made or not     ' Selecting the DIB Section into the DC to do drawing on it     oldDIB = SelectObject(DC, DIBSection) Else     Call DeleteDC(DC) ' If the DIB Section could not be made then delete the DC we made earlier End If End If End Sub Private Sub Grey4_Click() Dim X As Long, Y As Long, ti As Long ti = GetTickCount ' Now copying the Picturebox Image in the EMPTY DIB Section Call BitBlt(DC, 0, 0, Picture1.ScaleWidth, Picture1.ScaleHeight, Picture1.hdc, 0, 0, SRCCOPY) ' Getting the Pixel Array of the DIB Section ReDim bDIB(1 To Picture1.ScaleWidth, 1 To Picture1.ScaleHeight) As RGBQUAD ' The following API is the ONE which gets the Pixel Array of the DIB Section Call GetDIBits(DC, DIBSection, 0&, Picture1.ScaleHeight, bDIB(1, 1), bi.bmiHeader, 0&) ' We have to go through each and every pixel in the Bitmap For X = 1 To Picture1.ScaleWidth   For Y = 1 To Picture1.ScaleHeight         bDIB(X, Y).rgbBlue = 0.3 * bDIB(X, Y).rgbRed + 0.587 * bDIB(X, Y).rgbGreen + 0.114 * bDIB(X, Y).rgbBlue         bDIB(X, Y).rgbGreen = bDIB(X, Y).rgbBlue         bDIB(X, Y).rgbRed = bDIB(X, Y).rgbBlue   Next Y Next X ' Setting back the Pixel Array of the DIB Section Call SetDIBits(DC, DIBSection, 0&, Picture1.ScaleHeight, bDIB(1, 1), bi.bmiHeader, 0&) ' Copying the processed picture into the Picturebox Call BitBlt(Picture1.hdc, 0, 0, Picture1.ScaleWidth, Picture1.ScaleHeight, DC, 0, 0, SRCCOPY) MsgBox "Operation completed in " & GetTickCount - ti & " ms" End Sub Private Sub Form_Unload(Cancel As Integer) Call SelectObject(DC, oldDIB) Call DeleteObject(DIBSection) Call DeleteDC(DC) Erase bDIB() End Sub

     I'm not describing this function because its from the DIB Section article which I suppose the reader has allready read. But to be true this function is also taking 31 milliseconds to complete as the last one did. But this function gives you the scope behind how to map the structure of an organizational Image Processing project. Here we create the DIB Section in the begining and then just do all the things in the button_click subroutine. Now I must stop writing any new function. The fastest function of all functions remain the Grey3 because of many reasons. Firstly not wasting time in creating any new DIBs or DDBs, just directly getting-processing-setting back the pixel array of the picture allready present in the Picturebox. Grey3 completes the operation in 16 milliseconds which is quite fast when talking in terms of VB. But as I said there's no cure for the speed geeks. So get your minds on this topic and try to achieve the results in lesser than 16 milliseconds. And dont forget to send me a copy of your function...