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CreateLeadDC Method

Summary

Creates a Windows GDI device context using this Leadtools.RasterImage as the display surface.

Syntax

C#
VB
C++
public static IntPtr CreateLeadDC( 
   RasterImage image 
) 
Public Shared Function CreateLeadDC( _ 
   ByVal image As Leadtools.RasterImage _ 
) As IntPtr 
public: 
static IntPtr CreateLeadDC(  
   Leadtools.RasterImage^ image 
)  

Parameters

image
The source image.

Return Value

The Windows HDC object this method creates.

Remarks

This method allows you to create an infinite number of drawing capabilities such as paint, erase, color erase and brush, pen, spray gun, flood fill, color tube, text overlay, curve, line, rectangle, polygon, ellipse, freehand shapes, cut and paste, and more.

All Windows GDI functions can be used to draw to the image using the returned HDC. The HDC must be freed with the DeleteLeadDC method.

If a region is defined for the image, GDI functions act only on the region, not on the entire image.

The DIB driver supports only 1, 4, 8, 16 and 24 bit images. If you are using an image that has some other number of bits per pixel, you must use Leadtools.ImageProcessing.ColorResolutionCommand to change the image to a bits per pixel value supported by the DIB driver.

For more information refer to RasterImage and GDI/GDI+.

For more information, refer to Introduction to Image Processing With LEADTOOLS.

Example

This example draws an ellipse on a raster image.

C#
VB
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.Drawing; 
using Leadtools.ImageProcessing; 
 
public void CreateLeadDCExample() 
{ 
   RasterCodecs codecs = new RasterCodecs(); 
   RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp")); 
 
   LeadPoint point1 = new LeadPoint(image.Width / 8, image.Height / 8); 
   LeadPoint point2 = new LeadPoint(image.Width / 2, image.Height / 2); 
 
   // Convert the coordinates if necessary. 
   if (image.ViewPerspective != RasterViewPerspective.TopLeft) 
   { 
      point1 = image.PointToImage(RasterViewPerspective.TopLeft, point1); 
      point2 = image.PointToImage(RasterViewPerspective.TopLeft, point2); 
   } 
 
   // Create the device context 
   IntPtr hdc = RasterImagePainter.CreateLeadDC(image); 
   using (Graphics g = Graphics.FromHdc(hdc)) 
   { 
      g.DrawEllipse(new Pen(Color.White), point1.X, point1.Y, point2.X - point1.X, point2.Y - point1.Y); 
   } 
   RasterImagePainter.DeleteLeadDC(hdc); 
 
   codecs.Save(image, Path.Combine(LEAD_VARS.ImagesDir, "Imahe1_CreateLeadDC.bmp"), RasterImageFormat.Bmp, 0); 
 
   image.Dispose(); 
   codecs.Dispose(); 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images"; 
} 
Imports Leadtools 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
 
Public Sub CreateLeadDCExample() 
   Dim codecs As New RasterCodecs() 
   Dim image As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp")) 
 
   Dim point1 As New LeadPoint(image.Width \ 8, image.Height \ 8) 
   Dim point2 As New LeadPoint(image.Width \ 2, image.Height \ 2) 
 
   ' Convert the coordinates if necessary. 
   If image.ViewPerspective <> RasterViewPerspective.TopLeft Then 
      point1 = image.PointToImage(RasterViewPerspective.TopLeft, point1) 
      point2 = image.PointToImage(RasterViewPerspective.TopLeft, point2) 
   End If 
 
   ' Create the device context 
   Dim hdc As IntPtr = RasterImagePainter.CreateLeadDC(image) 
   Using g As Graphics = Graphics.FromHdc(hdc) 
      g.DrawEllipse(New Pen(Color.White), point1.X, point1.Y, point2.X - point1.X, point2.Y - point1.Y) 
   End Using 
   RasterImagePainter.DeleteLeadDC(hdc) 
 
   codecs.Save(image, Path.Combine(LEAD_VARS.ImagesDir, "Imahe1_CreateLeadDC.bmp"), RasterImageFormat.Bmp, 0) 
 
   image.Dispose() 
   codecs.Dispose() 
End Sub 
 
Public NotInheritable Class LEAD_VARS 
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images" 
End Class 

Requirements

Target Platforms

Help Version 19.0.2017.10.18
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Leadtools.Drawing Assembly