[Learning diary] acquisition and output of pixels in VB Image Processing

Pixel acquisition and output in VB Image Processing

Author: Region nameSource: InterNetTime added: 2005-1-28

To process an image, first obtain the pixel value of the image. Although the PICTURE control provided by VB can open many types of images, however, the POINT method provided by it is too slow to read pixels. The GetPixel API can be used quickly, because the PIONT method itself is a package for GetPixel. In VB, the DIB method is used to quickly obtain an image opened in PICTURE, and the DDB method is also used, however, the DDB method also needs to take into account the processing of images with different color depths separately. The implementation of the program is relatively complex, and the DIB method is not required, in addition, the processing speed is slower than that of the DDB method. Process 1: obtain all pixels of an image opened in the PICTURE control. Public Sub DibGet (ByVal IdSource As Long, XBegin As Long, ByVal YBegin As Long, ByVal XEnd As Long, ByVal YEnd As Long) Dim iBitmap As Long Dim iDC As Long Dim I As LongDim Dim W As Long Dim H As Long On Error GoTo ErrLine Done = False TimeGet = timeGetTime InPutWid = XEnd-XBegin InPutHei = YEnd-YBegin W = InPutWid + 1 H = InPutHei + 1 I = (Bits \ 8)-1 ReDim ColVal (I, InPutWid, InPutHei) With bi24BitInfo. bmiHeader . BiBitCount = Bits . BiCompression = 0 & . BiPlanes = 1 . BiSize = Len (bi24BitInfo. bmiHeader) . BiWidth = W . BiHeight = H End IBitmap = GetCurrentObject (IdSource, 7 &) GetDIBits IdSource, iBitmap, 0 &, H, ColVal (0, 0, 0), bi24BitInfo, 0 & DeleteObject iBitmap Done = True TimeGet = timeGetTime-TimeGetExit Sub ErrLine: MsgBox "error code:" & Err. Number & ":" & Err. Description End Sub In this process, only some parameter settings and API calls are used, and algorithms are not involved. Process 2: Process of image output: Public Sub DIBPut (ByVal IdDestination As Long) Dim W As Long Dim H As Long On Error GoTo ErrLine Done = False TimePut = timeGetTime W = OutPutWid + 1 H = OutPutHei + 1 With bi24BitInfo. bmiHeader . BiWidth = W . BiHeight = H LineBytes = (W * Bits + 31) And & HFFFFFFE0) \ 8 . BiSizeImage = LineBytes * H End SetDIBitsToDevice IdDestination, 0, 0, W, H, 0, 0, 0, H, ColOut (0, 0, 0), bi24BitInfo. bmiHeader, 0 Done = True TimePut = timeGetTime-TimePut Exit Sub ErrLine: MsgBox Err. Description End Sub The following describes the global variables, data structures, and API definitions in the process. API definition: Delete A DC Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long Delete an object Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long Select current object Private Declare Function GetCurrentObject Lib "gdi32" (ByVal hdc As Long, ByVal uObjectType As Long) As Long Obtain DIB 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 BitMapInfo, byVal wUsage As Long) As Long Obtain system time Private Declare Function timeGetTime Lib "winmm. dll" () As Long Data structure definition: Private Type BitMapInfoHeader 'file information header -- 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 RGBQuad RgbBlue As Byte RgbGreen As Byte RgbRed As Byte 'Rgbreserved As Byte End Type Private Type BitMapInfo BmiHeader As BitMapInfoHeader BmiColors As RGBQuad End Type These three data structures are indispensable in DIB. We don't have to go into it, but simply copy and paste them in order. Global variables used in the process: Private Const Bits As Long = 32' color depth. Here, all images are processed in 32 Bits. Public Done As Boolean 'is used to mark whether a process ends. Public TimeGet As Long is used to record the time spent in the input process Processing Public TimePut As Long is used to record the time spent in processing the output process Dim ColVal () As Byte 'is used to store the pixel value input from DIB Dim ColOut () As Byte 'is used to store the pixel value output to DIB. Dim InPutHei As Long is used to record the height of the input image Dim InPutWid As Long is used to record the width of the input image Dim bi24BitInfo As BitMapInfo 'defines BMP Information We can see that I used two different dynamic arrays ColVal () and ColOut () in the input and output, which makes sense, because we do not just want to input and output images, processing pixels is also required. Including image scaling, color adjustment, sharpening, softening, and so on. Using two different arrays to store data separately is more conducive to program implementation. Some impatient friends may have pasted the program into the project for trial use, but they will find that they cannot output images at all. This is because when the images you get with DIBGET are still in ColVal (), you need to put them in the ColOut () array to make the DIBPUT process take effect. Here is a process for moving the entire array of data: Public Sub CopyData (ByVal W As Long, ByVal H As Long) Dim Length As Long Dim I As Long Dim L As Long I = Bits \ 8 L = I-1 Length = (W + 1 &) * (H + 1 &) * I ReDim ColOut (L, W, H) CopyMemory ColOut (0, 0, 0), ColVal (0, 0, 0), Length End sub API definition: Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pDest As Any, pSrc As Any, ByVal ByteLen As Long) In this case, we can try the following: Adjust your monitor to 32-bit color. Paste all the preceding API and variable definitions to a new module. Create a new form and add two PICTURE controls: pictrue1 and picture2. One button is command1. Load an image in pictrue1 Write the following code in command1: Sub commandementclick () With picture1 . ScaleMode = 3 . BorderStyle = 0 DibGet. hdc, 0,. scalewidth,. scaleheight End CopyData InPutHei, InPutWid Picture2.AutoRedraw = True DibPut picture2.hdc Picture2.refresh End sub Run it, press the button, and the image in pictreu1 is immediately displayed in picture2. At this time, you may say that after such a long time, a picture will be posted? Can I use PaintPicture? Yes. If you only need to post a picture, you don't have to worry about it. However, the image processing part we will talk about later will use the front-door pixel value. So this is just the beginning. What I really want to talk about is still in the future. Please stay tuned.