ConvertFrom Method

Summary

Attempts to convert a specified object to an instance of RasterImage.

Syntax

C++/CLI

Python

public override object ConvertFrom( 
   ITypeDescriptorContext context, 
   CultureInfo culture, 
   object value 
)

public: 
Object^ ConvertFrom(  
   ITypeDescriptorContext^ context, 
   CultureInfo^ culture, 
   Object^ value 
) override

def ConvertFrom(self,context,culture,value):

Parameters

context
Type context information used for conversion.

culture
Cultural information that is respected during conversion.

value
The object being converted.

Return Value

A new instance of RasterImage.

Remarks

The ConvertFrom method will try to convert the object passed into the value parameter to a valid RasterImage object. For more information, refer to RasterImageTypeConverter.

Example

using Leadtools; 
using Leadtools.Codecs; 
 
using Leadtools.ImageProcessing.Core; 
 
public void RasterImageTypeConverterExample() 
{ 
   string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif"); 
 
   // Construct the source URL to use the source file and load the image 
   Uri uri = new Uri(srcFileName); 
 
   RasterCodecs codecs = new RasterCodecs(); 
 
   // Create a new instance of the RasterImageTypeConverter class 
   RasterImageTypeConverter rasterImageConverter = new RasterImageTypeConverter(codecs); 
 
   // We should be able to convert from a URL 
   Debug.Assert(rasterImageConverter.CanConvertFrom(uri.GetType())); 
 
   // Convert the image 
 
   // The return value from RasterImageTypeConverter.ConvertFrom might be an image that is 
   // still loading. So, we must subscribe to the RasterCodecs.LoadAsyncCompleteted 
   // event to obtain the finished image 
   codecs.LoadAsyncCompleted += new EventHandler<CodecsLoadAsyncCompletedEventArgs>(rasterImageTypeConverterExample_LoadAsyncCompleted); 
   object rasterImageObject = rasterImageConverter.ConvertFrom(uri); 
 
   // Notice that the returned rasterImageObject is a RasterImage with IsLoading set to true at this point 
   // The IsLoading will be false (and hence, the object will be usable) when the LoadAsyncCompleteted 
   // fires. 
} 
 
private void rasterImageTypeConverterExample_LoadAsyncCompleted(object sender, CodecsLoadAsyncCompletedEventArgs e) 
{ 
   // Check if the user canceled or if we have errors 
   if (e.Cancelled) 
   { 
      Debug.WriteLine("Canceled by the user"); 
   } 
   else if (e.Error != null) 
   { 
      Debug.WriteLine("Error: " + e.Error.Message); 
   } 
   else 
   { 
      // Everything is OK, get the image 
      RasterImage image = e.Image; 
 
      Debug.WriteLine("Image at {0} loaded OK, size: {1} by {2}", e.Uri, image.Width, image.Height); 
 
      image.Dispose(); 
   } 
 
   // Unsubscribe to the event and dispose the RasterCodecs object 
   RasterCodecs codecs = sender as RasterCodecs; 
   codecs.LoadAsyncCompleted -= new EventHandler<CodecsLoadAsyncCompletedEventArgs>(rasterImageTypeConverterExample_LoadAsyncCompleted); 
   codecs.Dispose(); 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS22\Resources\Images"; 
}

Requirements

Target Platforms

Reference

RasterImageTypeConverter Class

RasterImageTypeConverter Members

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Help Version 22.0.2023.5.5

Leadtools.Codecs Assembly

Introduction

Getting Started

Namespaces

Leadtools.Codecs Namespace

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