Grab Image ActiveX Control — Quick Start Guide for Developers

Grab Image ActiveX Control: Features, API Reference, and Examples

Overview

Grab Image ActiveX Control is a Windows COM component designed to capture, process, and stream images from cameras and video sources into desktop applications (VB6, VBA, VB.NET, C++, and other COM-capable hosts). This article summarizes common features, a compact API reference, and practical examples for integration and typical tasks.

Key Features

• Multi-source capture: Support for DirectShow-compatible cameras, TWAIN devices, and file-based sources (sequence of images, video files).
• Real-time preview: Low-latency live preview with adjustable frame rate and resolution.
• Image formats: Output as BMP, JPEG, PNG, or raw RGB buffers.
• Capture controls: Start/stop capture, single-frame grab, timed capture, and continuous streaming.
• Image processing hooks: Built-in basic filters (grayscale, resize, flip/rotate) and callback/event support for custom processing.
• Property configuration: Resolution, exposure, brightness, contrast, white balance, and compression quality.
• Thread-safe capture: Background acquisition with events marshaled to the main thread.
• Saving and export: Save to disk, stream to memory, or provide buffers to host application for further processing.
• Security & deployment: Strong-name/signature for registration, COM registration-free manifest support for side-by-side deployment.

Typical Use Cases

• Capturing snapshots from webcams for ID/photo kiosks.
• Integrating camera input into point-of-sale or inventory apps.
• Automating frame grabs from industrial cameras for QA.
• Building lightweight video recording or time-lapse utilities.
• Preprocessing images for OCR or barcode scanning pipelines.

API Reference (Common Methods, Properties, and Events)

Note: exact names may vary by vendor. This reference covers widely used patterns and recommended property/method names.

Core Methods

• Initialize(sourceID As String) As Long
  • Initializes the control with a specified source (device name, DirectShow filter, or file path). Returns status code.
• Start() As Long
  • Begins continuous capture/preview.
• Stop() As Long
  • Stops capture/preview.
• GrabFrame() As IPicture / ByteArray / Long
  • Captures a single frame and returns image data (IPicture for VB6, byte array or pointer for native code).
• SaveFrame(path As String, format As String, quality As Integer) As Long
  • Saves current frame to disk. format = “BMP”,“JPEG”,“PNG”.
• SetProperty(name As String, value As Variant) As Long
  • Generic setter for camera or control properties.
• GetProperty(name As String) As Variant
  • Generic getter.

Properties

• SourceList As String[] or Variant — available capture sources.
• CurrentSource As String — selected source ID.
• Width As Long, Height As Long — output resolution.
• FrameRate As Double — frames per second.
• PixelFormat As String — “RGB24”,“RGB32”,“GRAY8”, etc.
• CompressionQuality As Integer — 0–100 for JPEG.
• AutoExposure, AutoWhiteBalance As Boolean — toggles for automated camera controls.
• BufferCount As Integer — number of frames buffered.

Events / Callbacks

• OnFrameAvailable(image As IPicture / ByteArray)
  • Fired each time a new frame is ready.
• OnError(errorCode As Long, description As String)
  • Error notification.
• OnPropertyChanged(name As String, value As Variant)
  • Property change notification.

Examples

1) VB6 — Basic preview and snapshot

Code (VB6-style):

vb
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’ Place the ActiveX control on a form as GrabCtrl Private Sub Form_Load()GrabCtrl.Initialize “0” ‘ use first camera   GrabCtrl.Width = 640   GrabCtrl.Height = 480   GrabCtrl.Start End Sub

 
Private Sub cmdSnap_Click()   Dim img As IPicture   Set img = GrabCtrl.GrabFrame()   SavePicture img, App.Path & “\snapshot.jpg” End Sub
 
Private Sub FormUnload(Cancel As Integer)   GrabCtrl.Stop End Sub 

vb
 ffON2NH02oMAcqyoh2UU MQCbz04ET5EljRmK3YpQ CPXAhl7VTkj2dHDyAYAf” data-copycode=“true” role=“button” aria-label=“Copy Code”>Copy CodeCopied
Sub InsertSnapshot()   Dim g As Object   Set g = CreateObject(“Vendor.GrabImageControl”)   g.Initialize “0”   g.Width = 320: g.Height = 240   g.Start   Dim img As IPicture   Set img = g.GrabFrame()   g.Stop   ’ Insert into worksheet   ActiveSheet.Pictures.Insert SavePictureToTempFile(img, “temp.jpg”) End Sub 

vbnet
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Dim grab As New Vendor.GrabImageControl()
grab.Initialize(“0”)
grab.Width = 1280 : grab.Height = 720
AddHandler grab.OnFrameAvailable, AddressOf FrameReady grab.Start()

Private Sub FrameReady(ByVal imgData As Byte())
  ’ Convert byte[] to Bitmap, display in PictureBox, or process
  Using ms As New IO.MemoryStream(imgData)
    Dim bmp As New Bitmap(ms)
    PictureBox1.Image = New Bitmap(bmp)
  End Using
End Sub