注意：当创建一个从未被 LibTiff.Net 库更改过的新 tiff 图像时，我可以使用 LibTiff.Net 库毫无问题地添加/更改标签（第一次）。
无论如何，在我使用 LibTiff.Net 库更改 tiff 标签后，当我再次尝试更改它们时，图像已损坏。标签似乎很好，但图像本身显示为黑色图像（损坏）。
这是目前我在课堂上使用的标签扩展器......
private static Tiff.TiffExtendProc m_parentExtender;
private static List<TIFFTAGS_TAG> m_lTagsToWrite;
private static void TagExtender(Tiff tif)
{
List<TiffFieldInfo> tfInfo = new List<TiffFieldInfo>();
Int16 readCount = 0;
Int16 writeCount = 0;
bool okToChange = false;
bool passCount = false;
//Make sure to create a new tiff field info for all the tags to be written
foreach (TIFFTAGS_TAG ttTag in m_lTagsToWrite)
{
switch (ttTag.TagType)
{
case TIFFTAGS_TAG_DATATYPE.ASCII:
readCount = -1;
writeCount = -1;
okToChange = true;
passCount = false;
break;
case TIFFTAGS_TAG_DATATYPE.LONG:
case TIFFTAGS_TAG_DATATYPE.RATIONAL:
case TIFFTAGS_TAG_DATATYPE.SHORT:
readCount = 2;
writeCount = 2;
okToChange = false;
passCount = true;
break;
}
if (ttTag.TagType != TIFFTAGS_TAG_DATATYPE.UNKNOWN)
{
//Add the new item to the list
tfInfo.Add(new TiffFieldInfo((TiffTag)ttTag.TagNumber, readCount, writeCount, (TiffType)ttTag.TagType, FieldBit.Custom, okToChange, passCount, ttTag.TagName));
}
}
//Turn the list into an array again
TiffFieldInfo[] tfInfoArray = tfInfo.ToArray();
//Add the fields to the main field info area
tif.MergeFieldInfo(tfInfoArray, tfInfoArray.Length);
//Propergate the chain if needed
if (m_parentExtender != null)
m_parentExtender(tif);
}
这是目前我用来在给定 tiff 上设置 tiff 标签的函数
public static bool SetTiffTags(string sFileName, List<TIFFTAGS_TAG> ttTagsInfo)
{
//Sets all the tiff tags in the image given.
//Returns true if successful or false if error occured
//Check if the file exists
if (!File.Exists(sFileName))
{
//File does not exist
return false;
}
try
{
//Set the tag info so that it can be carried over to the extender callback
m_lTagsToWrite = new List<TIFFTAGS_TAG>();
m_parentExtender = Tiff.SetTagExtender(TagExtender);
m_lTagsToWrite = ttTagsInfo;
using (Tiff tImage = Tiff.Open(sFileName, "a"))
{
if (tImage != null)
{
//Go to the first page
tImage.SetDirectory(0);
foreach (TIFFTAGS_TAG ttTag in ttTagsInfo)
{
switch (ttTag.TagType)
{
case TIFFTAGS_TAG_DATATYPE.ASCII:
try
{
//string
string sValue = ttTag.Value.ToString();
tImage.SetField((TiffTag)ttTag.TagNumber, sValue);
}
catch
{
//Could not convert to a string
return false;
}
break;
case TIFFTAGS_TAG_DATATYPE.LONG:
try
{
//long
int[] iValues;
if (ttTag.Value.GetType().ToString() == "System.Int32")
{
iValues = new int[] { (int)ttTag.Value };
}
else if (ttTag.Value.GetType().ToString() == "System.Int32[]")
{
iValues = (int[])ttTag.Value;
}
else return false;
tImage.SetField((TiffTag)ttTag.TagNumber, iValues.Count(), iValues);
}
catch
{
//Could not convert to a long
return false;
}
break;
case TIFFTAGS_TAG_DATATYPE.SHORT:
try
{
//short
Int16[] iValues;
if (ttTag.Value.GetType().ToString() == "System.Int16")
{
iValues = new Int16[] { (Int16)ttTag.Value };
}
else if (ttTag.Value.GetType().ToString() == "System.Int16[]")
{
iValues = (Int16[])ttTag.Value;
}
else return false;
tImage.SetField((TiffTag)ttTag.TagNumber, iValues.Count(), iValues);
}
catch
{
//Could not convert to a short
return false;
}
break;
case TIFFTAGS_TAG_DATATYPE.RATIONAL:
try
{
//float
Single[] iValues;
if (ttTag.Value.GetType().ToString() == "System.Single")
{
iValues = new Single[] { (Single)ttTag.Value };
}
else if (ttTag.Value.GetType().ToString() == "System.Single[]")
{
iValues = (Single[])ttTag.Value;
}
else return false;
tImage.SetField((TiffTag)ttTag.TagNumber, iValues.Count(), iValues);
}
catch
{
//Could not convert to a single
return false;
}
break;
default:
//This type of tag is not supported so error out
return false;
}
}
//Write the information to the tiff
tImage.CheckpointDirectory();
}
else
{
//Restore previous tag extender
Tiff.SetTagExtender(m_parentExtender);
return false;
}
}
//Restore previous tag extender
Tiff.SetTagExtender(m_parentExtender);
}
catch
{
//Restore previous tag extender
Tiff.SetTagExtender(m_parentExtender);
return false;
}
//Return success
return true;
}