Paint(RasterImage,IntPtr,LeadRect,LeadRect,RasterPaintProperties) Method

Displays this Leadtools.RasterImage in the given Windows device context handle.

Syntax

Visual Basic
C#
Objective-C
Java
C++

public static void Paint( 
   RasterImage image,
   IntPtr hdc,
   LeadRect srcRect,
   LeadRect destRect,
   RasterPaintProperties properties
)

'Declaration
 
Public Overloads Shared Sub Paint( _
   ByVal image As RasterImage, _
   ByVal hdc As IntPtr, _
   ByVal srcRect As LeadRect, _
   ByVal destRect As LeadRect, _
   ByVal properties As RasterPaintProperties _
)

'Usage
 
Dim image As RasterImage
Dim hdc As IntPtr
Dim srcRect As LeadRect
Dim destRect As LeadRect
Dim properties As RasterPaintProperties
 
RasterImagePainter.Paint(image, hdc, srcRect, destRect, properties)

public:
static void Paint( 
   RasterImage^ image,
   IntPtr hdc,
   LeadRect srcRect,
   LeadRect destRect,
   RasterPaintProperties properties
)

Parameters

image

The source image.

hdc

The destination Windows device context where the image will be displayed.

srcRect

A Leadtools.LeadRect object that specifies the part of the image to use as the display source.

The coordinates of the srcRect are relative to the image. You can pass Rectangle.Empty to use the default, which matches the image.

destRect

Leadtools.LeadRect

A Leadtools.LeadRect object that determines how the image is scaled and positioned in hdc.

The coordinates of destRect are relative to the hdc handle. There is no default for this parameter. You must specify the Leadtools.LeadRect values.

properties

Options for the display.

Remarks

If the destination device context handle has fewer colors than the image, this method dithers the output to that display surface without affecting the actual image data.

This method lets you specify a source rectangle (with coordinates relative to the image) and a destination rectangle (with coordinates relative to the destination device context). Scaling of the displayed image depends on the relationship between these two rectangles, as shown in the following illustration:

Note: These illustrations are for an image with a RasterViewPerspective.TopLeft view perspective. For an explanation of image coordinates and view perspectives, refer to Accounting for View Perspective. If the image is not in RasterViewPerspective.TopLeft view perspective, refer to Changing Image Coordinates.

In addition, you can specify a clipping area within either rectangle to limit the area to be painted. For the destination rectangle, a clipping area is commonly specified to repaint part of the image that was temporarily covered up. For a source rectangle, you can use a clipping area to update the display when only part of the image in the source rectangle has changed.

The following illustration shows how specifying a source clipping area affects the display. Text has been added to the source image (using the image as a display surface), and the source clipping area specifies the area to be repainted.

You can specify the various rectangles in any way that meets your needs. Coordinates can have negative values and they can extend beyond the bounds of the image or destination device context. In fact, it is common for the display rectangle to be bigger than the destination device context dimension, where scroll bars are used to see different parts of the image.

In simple cases, you can use this method as follows:

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

For more information, refer to Changing Image Coordinates.

For more information, refer to Handling Palette Changes.

For more information, refer to Flags for the PaintDisplayMode Property.

Example

Visual Basic
C#
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Copy Code

Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.Drawing
Imports Leadtools.ImageProcessing

Public Sub PaintDCExample()
   Dim f As New PaintDCForm()
   f.ShowDialog()
End Sub

Class PaintDCForm
   Inherits Form
   Private image As RasterImage
   Private props As RasterPaintProperties

   Public Sub New()
      ' Load the image
      Dim codecs As New RasterCodecs()

      Dim srcFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif")
      image = codecs.Load(srcFileName)

      Text = "Normal - doubleclick to change."
      props = RasterPaintProperties.Default
      props.PaintDisplayMode = RasterPaintDisplayModeFlags.None
      props.UsePaintPalette = True
   End Sub

   Protected Overrides Sub Dispose(ByVal disposing As Boolean)
      ' Clean up
      If disposing Then
         image.Dispose()
      End If

      MyBase.Dispose(disposing)
   End Sub

   Protected Overrides Sub OnDoubleClick(ByVal e As EventArgs)
      If (props.PaintDisplayMode And RasterPaintDisplayModeFlags.ScaleToGray) = RasterPaintDisplayModeFlags.ScaleToGray Then
         Text = "Normal - doubleclick to change."
         props.PaintDisplayMode = props.PaintDisplayMode And Not RasterPaintDisplayModeFlags.ScaleToGray
      Else
         Text = "ScaleToGray - doubleclick to change."
         props.PaintDisplayMode = props.PaintDisplayMode Or RasterPaintDisplayModeFlags.ScaleToGray
      End If

      Invalidate()

      MyBase.OnDoubleClick(e)
   End Sub

   Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
      ' Draw the image fit and center on this form
      Dim destRect As LeadRect = LeadRect.FromLTRB(ClientRectangle.Left, ClientRectangle.Top, ClientRectangle.Right, ClientRectangle.Bottom)
      destRect = RasterImage.CalculatePaintModeRectangle( _
         image.ImageWidth, _
         image.ImageHeight, _
         destRect, _
         RasterPaintSizeMode.Fit, _
         RasterPaintAlignMode.Center, _
         RasterPaintAlignMode.Center)

      Dim hdc As IntPtr = e.Graphics.GetHdc()
      RasterImagePainter.Paint(image, hdc, LeadRect.Empty, destRect, props)
      e.Graphics.ReleaseHdc(hdc)

      MyBase.OnPaint(e)
   End Sub
End Class

Public NotInheritable Class LEAD_VARS
Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

using Leadtools;
using Leadtools.Codecs;
using Leadtools.Drawing;
using Leadtools.ImageProcessing;

public void PaintDCExample()
{
   PaintDCForm f = new PaintDCForm();
   f.ShowDialog();
}

class PaintDCForm : Form
{
   private RasterImage image;
   private RasterPaintProperties props;

   public PaintDCForm()
   {
      // Load the image
      RasterCodecs codecs = new RasterCodecs();

      string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif");
      image = codecs.Load(srcFileName);

      Text = "Normal - doubleclick to change.";
      props = RasterPaintProperties.Default;
      props.PaintDisplayMode = RasterPaintDisplayModeFlags.None;
      props.UsePaintPalette = true;
   }

   protected override void Dispose(bool disposing)
   {
      // Clean up
      if(disposing)
      {
         image.Dispose();
      }

      base.Dispose(disposing);
   }

   protected override void OnDoubleClick(EventArgs e)
   {
      if((props.PaintDisplayMode & RasterPaintDisplayModeFlags.ScaleToGray) == RasterPaintDisplayModeFlags.ScaleToGray)
      {
         Text = "Normal - doubleclick to change.";
         props.PaintDisplayMode &= ~RasterPaintDisplayModeFlags.ScaleToGray;
      }
      else
      {
         Text = "ScaleToGray - doubleclick to change.";
         props.PaintDisplayMode |= RasterPaintDisplayModeFlags.ScaleToGray;
      }

      Invalidate();

      base.OnDoubleClick(e);
   }

   protected override void OnPaint(PaintEventArgs e)
   {
      // Draw the image fit and center on this form
      LeadRect destRect = LeadRect.FromLTRB(ClientRectangle.Left, ClientRectangle.Top, ClientRectangle.Right, ClientRectangle.Bottom);
      destRect = RasterImage.CalculatePaintModeRectangle(
         image.ImageWidth,
         image.ImageHeight,
         destRect,
         RasterPaintSizeMode.Fit,
         RasterPaintAlignMode.Center,
         RasterPaintAlignMode.Center);

      IntPtr hdc = e.Graphics.GetHdc();
      RasterImagePainter.Paint(image, hdc, LeadRect.Empty, destRect, props);
      e.Graphics.ReleaseHdc(hdc);

      base.OnPaint(e);
   }
}

static class LEAD_VARS
{
public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}

Requirements

Target Platforms

Reference

RasterImagePainter Class
RasterImagePainter Members
Overload List