RasterRegionXForm Class

Summary

Provides data for translating between region coordinates and external representations of those coordinates.

Syntax

Objective-C

C++/CLI

Java

Python

public class RasterRegionXForm

@interface LTRasterRegionXForm : NSObject

public class RasterRegionXForm

public ref class RasterRegionXForm

class RasterRegionXForm:

Remarks

All region methods accept a null reference. In that case, no transformation occurs. The scalar fields default to 1, the offsets default to 0, and the view perspective defaults to the image view perspective.

Several of the LEADTOOLS methods for creating and working with an image region use coordinates from an external representation of the region, such as a shape drawn in a device context. To compensate for possible differences in view perspective, scaling, and display offsets, these LEADTOOLS methods require that you provide translation information in an RasterRegionXForm object.

In most cases, the external representation of an image region is scaled and positioned relative to the display coordinates of a LEADTOOLS painting method. Therefore, the following table describes the fields to set in the RasterRegionXForm object, based on the parameters of the display methods.

When assigning an external representation to an image, every point (Xa, Ya) in the an external representation is transformed (by RasterRegionXForm) to point (Xc, Yc) in the image region as follows:

Add offsets: Xb = Xa + XForm.XOffset Yb = Ya + XForm.YOffset
Multiply by scalars: Xc = (Xb * XForm.XScalarNumerator) / XForm.XScalarDenominator Yc = (Yb * XForm.YScalarNumerator) / XForm.YScalarDenominator
Compensate for view perspective (updating Xc and Yc in place): PointToImage(XForm.ViewPerspective, Xc, Yc)

When retrieving an external representation from an image, every point (Xa, Ya) in the image region is transformed (by RasterRegionXForm) to point (Xc, Yc) in the external region as follows:

Compensate for view perspective (updating Xa and Ya in place): PointFromImage(XForm.ViewPerspective, Xa, Ya)
Multiply by scalars: Xb = (Xa * XForm.XScalarNumerator) / XForm.XScalarDenominator Yb = (Ya * XForm.YScalarNumerator) / XForm.YScalarDenominator
Add offsets: Xc = Xb + XForm.XOffset Yc = Yb + XForm.YOffset

For more information, refer to Translating Coordinates for a Region..

Example

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
 
 
public void RasterRegionTransformExample() 
{ 
   string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp"); 
   string destFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1_TransformRegion.bmp"); 
   using (RasterCodecs codecs = new RasterCodecs()) 
   { 
      // Load the source image 
      using (RasterImage image = codecs.Load(srcFileName, 0, CodecsLoadByteOrder.BgrOrGray, 1, 1)) 
      { 
         // Add a large elliptical region  
         image.AddEllipseToRegion(null, new LeadRect(0, 0, image.ImageWidth, image.ImageHeight), RasterRegionCombineMode.Set); 
 
         // Fill the image with yellow 
         FillCommand cmd = new FillCommand(RasterColor.FromKnownColor(RasterKnownColor.Yellow)); 
         cmd.Run(image); 
 
         // Get the region 
         using (RasterRegion region = image.GetRegion(null)) 
         { 
            // Transform this region by making it twice as small 
            LeadRect bounds = region.GetBounds(); 
 
            RasterRegionXForm xform = RasterRegionXForm.Default; 
 
            xform.XScalarNumerator = 1; 
            xform.XScalarDenominator = 2; 
            xform.YScalarNumerator = 1; 
            xform.YScalarDenominator = 2; 
 
            xform.XOffset = bounds.Width / 2; 
            xform.YOffset = bounds.Height / 2; 
 
            region.Transform(xform); 
 
            // Re-set this region into the image 
            image.SetRegion(null, region, RasterRegionCombineMode.Set); 
         } 
 
         // Now fill with red and save 
         cmd = new FillCommand(RasterColor.FromKnownColor(RasterKnownColor.Red)); 
         cmd.Run(image); 
 
         codecs.Save(image, destFileName, RasterImageFormat.Bmp, 24); 
      } 
   } 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS22\Resources\Images"; 
}