RasterMarkerMetadata Class

Summary

Extends the RasterMetadata class to provide functionality for dealing with marker metadata stored within various image file formats.

Syntax

Objective-C

C++

Java

[SerializableAttribute()] 
public class RasterMarkerMetadata : RasterMetadata

<SerializableAttribute()> 
Public Class RasterMarkerMetadata  
   Inherits RasterMetadata

@interface LTRasterMarkerMetadata : LTRasterMetadata

public class RasterMarkerMetadata extends RasterMetadata implements Serializable

[SerializableAttribute()] 
public ref class RasterMarkerMetadata : public RasterMetadata

Remarks

JPEG files contain metadata information in user-defined markers.

The user-defined markers are in the range 0xE0 to 0xFE. These markers can have a maximum size of 0xFFFD, or 65533 bytes.

The markers below 0xE0 are reserved for the encoding of the image and inserting a reserved marker can make a file invalid. Therefore, you should not use reserved markers unless you are well acquainted with markers and image encoding in JPEG files.

TIFF files do not contain markers, however, LEADTOOLS provides a "workaround" for transferring Exif comments from JPEG files to TIFF files, and vice versa. The Exif metadata information from a TIFF file will be loaded as an APP1 marker. Therefore, you can load Exif metadata from an uncompressed file and store it in a compressed Exif file.

You can also take metadata information from a compressed Exif file and store it in an uncompressed Exif file. Please note however, that some information cannot be stored inside uncompressed Exif files. For example, audio data is stored in APP2 markers and there is no built-in support for saving APP2 markers in TIFF files. However, you can still save the audio data yourself, using a custom tag.

Example

This example will write different markers to an existing TIF file then read them as a test.

using Leadtools; 
using Leadtools.Codecs; 
 
 
public void RasterMarkerMetadataExample() 
{ 
	RasterCodecs codecs = new RasterCodecs(); 
	codecs.ThrowExceptionsOnInvalidImages = true; 
 
	string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp"); 
	string destFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1_markers.tif"); 
 
	// Load the image 
	RasterImage image = codecs.Load(srcFileName); 
	codecs.Save(image, destFileName, RasterImageFormat.ExifJpeg, 24); 
 
	image.Dispose(); 
 
	// write a marker to the file 
	RasterMarkerMetadata markerWrite = new RasterMarkerMetadata(); 
	byte[] data = new byte[100]; 
	for (int i = 0; i < data.Length; i++) 
		data[i] = (byte)(i + 1); 
	markerWrite.Id = 0xE0; 
	markerWrite.SetData(data); 
 
	Console.WriteLine("Writing the marker"); 
	codecs.WriteMarker(destFileName, 1, markerWrite); 
 
	// read the markers from the file and check for ours 
	IList<RasterMarkerMetadata> markers = codecs.ReadMarkers(destFileName); 
	RasterMarkerMetadata markerRead = null; 
	for (int i = 0; i < markers.Count && markerRead == null; i++) 
	{ 
		if (markers[i].Id == markerWrite.Id) 
			markerRead = markers[i]; 
	} 
 
	Assert.IsTrue(markerRead.Id == markerWrite.Id); 
	byte[] dataRead = markerRead.GetData(); 
	byte[] dataWrite = markerWrite.GetData(); 
	Assert.IsTrue(dataRead.Length == dataWrite.Length); 
	for (int i = 0; i < dataRead.Length; i++) 
		Assert.IsTrue(dataRead[i] == dataWrite[i]); 
 
	codecs.Dispose(); 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS21\Resources\Images"; 
}

Imports Leadtools 
Imports Leadtools.Codecs 
 
Public Sub RasterMarkerMetadataExample() 
   Dim codecs As RasterCodecs = New RasterCodecs() 
   codecs.ThrowExceptionsOnInvalidImages = True 
 
   Dim srcFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp") 
   Dim destFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Image1_markers.tif") 
 
   ' Load the image 
   Dim image As RasterImage = codecs.Load(srcFileName) 
   codecs.Save(image, destFileName, RasterImageFormat.ExifJpeg, 24) 
 
   image.Dispose() 
 
   ' write a marker to the file 
   Dim markerWrite As RasterMarkerMetadata = New RasterMarkerMetadata() 
   Dim data As Byte() = New Byte(99) {} 
   Dim i As Integer = 0 
   Do While i < data.Length 
      data(i) = CByte(i + 1) 
      i += 1 
   Loop 
   markerWrite.Id = &HE0 
   markerWrite.SetData(data) 
 
   Console.WriteLine("Writing the marker") 
   codecs.WriteMarker(destFileName, 1, markerWrite) 
 
   ' read the markers from the file and check for ours 
   Dim markers As IList(Of RasterMarkerMetadata) = codecs.ReadMarkers(destFileName) 
   Dim markerRead As RasterMarkerMetadata = Nothing 
   i = 0 
   Do While i < markers.Count AndAlso markerRead Is Nothing 
      If markers(i).Id = markerWrite.Id Then 
         markerRead = markers(i) 
      End If 
      i += 1 
   Loop 
 
   Debug.Assert(markerRead.Id = markerWrite.Id) 
   Dim dataRead As Byte() = markerRead.GetData() 
   Dim dataWrite As Byte() = markerWrite.GetData() 
   Debug.Assert(dataRead.Length = dataWrite.Length) 
   i = 0 
   Do While i < dataRead.Length 
      Debug.Assert(dataRead(i) = dataWrite(i)) 
      i += 1 
   Loop 
End Sub 
 
Public NotInheritable Class LEAD_VARS 
   Public Const ImagesDir As String = "C:\LEADTOOLS21\Resources\Images" 
End Class

Requirements

Target Platforms

Reference

RasterMarkerMetadata Members

Leadtools Namespace

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