How to add gif and tiff support to TJvDBImage? - delphi

Question

TJvDBImage is a good component that support several picture formats. In JvJVCLUtils, it mentioned that the supported format can be expanded by RegisterGraphicSignature procedure. In the comment it mentioned :
WHAT IT IS:
These are helper functions to register graphic formats than can
later be recognized from a stream, thus allowing to rely on the actual
content of a file rather than from its filename extension.
This is used in TJvDBImage and TJvImage.
IMAGE FORMATS:
The implementation is simple: Just register image signatures with
RegisterGraphicSignature procedure and the methods takes care
of the correct instantiation of the TGraphic object. The signatures
register at unit's initialization are: BMP, WMF, EMF, ICO, JPG.
If you got some other image library (such as GIF, PCX, TIFF, ANI or PNG),
just register the signature:
RegisterGraphicSignature(<string value>, <offset>, <class>)
or
RegisterGraphicSignature([<byte values>], <offset>, <class>)
This means:
When <string value> (or byte values) found at <offset> the graphic
class to use is <class>
For example (actual code of the initialization section):
RegisterGraphicSignature([$D7, $CD], 0, TMetaFile); // WMF
RegisterGraphicSignature([1, 0], 0, TMetaFile); // EMF
RegisterGraphicSignature('JFIF', 6, TJPEGImage);
You can also unregister signature. IF you want use TGIFImage instead of
TJvGIFImage, you can unregister with:
UnregisterGraphicSignature('GIF', 0);
or just
UnregisterGraphicSignature(TJvGIFImage); // must add JvGIF unit in uses clause
then:
RegisterGraphicSignature('GIF', 0, TGIFImage); // must add GIFImage to uses clause
I follow the instruction and Added GIFImage in the uses clause at that unit. Also, in procedure GraphicSignaturesNeeded I added :
RegisterGraphicSignature('GIF', 0, TGIFImage);
RegisterGraphicSignature([$4D, $4d, 0, $2A], 0, TWICImage); // TIFF
RegisterGraphicSignature([$49, $49, $2A, 0], 0, TWICImage); // TIFF
The TIFF info is based on
Tip: detecting graphic formats
Then I used the makemodified.bat to re-compile JVCL.
Before the change, loading image to the TJvDBImage will load the file and give endless error of "bitmap image not valid". After change, it refuse to load the file and give the same error for 1 time.
If I load GIF / TIFF image to the field using other tools, when displaying , it give endless error mentioned above. If I load the field content using the above link functions, it can display in a TImage perfectly.
So, what have I missed or doing wrong?
Thank you!