VFP show from multi page tiff first page only. If you want extract some page to independently files, you can use class _XFRX_TIFF_WRITER.
This example is for XFRX 20.0. Parameter tuAppendToFile is equal to parameter tuAppend in SetParams() method.
Append source file to end destination file
LOCAL m.lcSource, m.lcDestination, m.tuAppendToFile, m.loTIFF
m.lcSource="input.tiff" && Input file
m.lcDestination="output_.tiff" && Destination file
m.tuAppendToFile=.T. && Append to end
SET PROCEDURE TO xfrx.prg
m.loTIFF=CREATEOBJECT("_XFRX_TIFF_WRITER")
?m.loTIFF.AppendPages(m.lcSource, m.lcDestination, m.tuAppendToFile)
Append source file begin first page of destination file
LOCAL m.lcSource, m.lcDestination, m.tuAppendToFile, m.loTIFF
m.lcSource="input.tiff" && Input file
m.lcDestination="output.tiff" && Destination file
m.tuAppendToFile=1 && Append before first page
SET PROCEDURE TO xfrx.prg
m.loTIFF=CREATEOBJECT("_XFRX_TIFF_WRITER")
?m.loTIFF.AppendPages(m.lcSource, m.lcDestination, m.tuAppendToFile)
Replace third page in destination file
LOCAL m.lcSource, m.lcDestination, m.tuAppendToFile, m.loTIFF
m.lcSource="input.tiff" && Input file
m.lcDestination="output_.tiff" && Destination file
m.tuAppendToFile="R3" && Replace third page
SET PROCEDURE TO xfrx.prg
m.loTIFF=CREATEOBJECT("_XFRX_TIFF_WRITER")
?m.loTIFF.AppendPages(m.lcSource, m.lcDestination, m.tuAppendToFile)