virtual L_INT LFile::ReadTag(uTag, pType, pCount, pLBuffer, pLoadFileOption=NULL)
Gets the specified tagged data from a TIFF file. This function is provided to support TIFF tags that you define.
Tag to identify the data in the TIFF file. Use the same tag that you specified in the LFileSettings::SetTag function. Examples of registered tags are:
0x8298 | Copyright comment |
---|---|
0x8769 | General Exif comments |
0x8825 | Exif GPS comments |
0x80A4 | Annotation TIFF tag defined as ANNTAG_TIFF. |
Address of the variable to be updated with the tagged data type. The following are possible values:
Value | Meaning |
---|---|
TAG_BYTE | [1] Byte. |
TAG_ASCII | [2] Byte in the range of 0 to 255. |
TAG_SBYTE | [6] Byte used as signed number in the range of -128 to +127. |
TAG_UNDEFINED | [7] Byte, with application-defined usage. |
TAG_SHORT | [3] Two bytes, unsigned. |
TAG_SSHORT | [8] Two bytes, signed. |
TAG_LONG | [4] Four bytes, unsigned. |
TAG_SLONG | [9] Four bytes, signed. |
TAG_RATIONAL | [5] Eight bytes, used as a pair of unsigned long integers, where the first number is the numerator and the second is the denominator of a fraction. |
TAG_SRATIONAL | [10] Eight bytes, used as a pair of signed long integers, where the first number is the numerator and the second is the denominator of a fraction. |
TAG_FLOAT | [11] Four bytes used as a floating point number. |
TAG_DOUBLE | [12] Eight bytes used as a double-precision floating point number. |
TAG_IFD | [13] 32-bit IFD offset. |
TAG_LONG8 | [16] Unsigned 64-bit integer (valid only for BigTIFF formats). |
TAG_SLONG8 | [17] Signed 64-bit integer (valid only for BigTIFF formats). |
TAG_IFD8 | [18] 64-bit IFD offset (valid only for BigTIFF formats). |
Address of the variable to be updated with the count of data items. The count is based on the tagged data type. For example, if the count is 2 and the data type is TAG_DOUBLE, the required buffer size is 16.
Pointer to the buffer to be updated with the data. You can pass NULL if you want to use this function's return value to determine the required buffer size.
Pointer to optional extended load options. Pass NULL to use the default load options.
Value | Meaning |
---|---|
SUCCESS | The function was successful. |
< 1 | An error occurred. Refer to Return Codes. |
It is often convenient to call this function twice, as follows:
For general information about TIFF tags, refer to Implementing TIFF Comments and Tags.
Win32, x64.
L_INT LFile__ReadTagExample()
{
L_INT nRet;
L_UINT16 LogoPosition = 0x8001; // my private tag
L_UINT16 TagType; // tagged data type
L_UINT32 TagCount; // count of data items
L_INT32 BufferSize; // required size of the buffer
LFile LeadFile;
LBuffer LeadBuffer;
LeadFile.SetFileName(MAKE_IMAGE_PATH(TEXT("clean.tif")));
// Get the required buffer size
BufferSize = LeadFile.ReadTag( LogoPosition, &TagType, &TagCount, NULL);
// Allocate and lock the buffer
if ((TagType == TAG_SSHORT) && (BufferSize > 0))
{
nRet = LeadBuffer.Reallocate(BufferSize);
if(nRet != SUCCESS)
return nRet;
}
else
return FAILURE ;
// Get the tagged data
nRet = LeadFile.ReadTag( LogoPosition, &TagType, &TagCount, &LeadBuffer);
if(nRet < 1)
return nRet;
return SUCCESS;
}
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