src/tiff/contrib/win_dib/README.Tiffile

Frank,

I attached a file that uses RGBA interface (tif_getimage.c) to read a tiff
file and convert to a DIB.  It's advantage is that it is easy to read *any*
tiff file suported by libtiff and easily convert it to a DIB.  The disadvantage
is that bilevel (B&W) bitmaps (and all other non-rgba images) are also
converted to RGBA, thus taking up 32x as much memory as needed (4 bytes per
pixel, rather than 1 bit).  I read tiff files, but don't need to
write them.  And my files are typically small, so the overhead is mostly
inconsequential.  But for bilevel images, I overrode the get() and put()
routines of the RGBA interface to just copy the data from the input raster
to the output raster, rather than expanding out to full 32 bit format.  It
would be nice if there were a simple way to handle all palletized images,
but that would take more custom routines, and it's not that important to me.

Usage:

    m_pDIB = (PBITMAPINFOHEADER)::ReadTIFF(pathName);
    if (m_pDIB != 0) {
       m_format = IMAGETYPE_TIF;
    }

This is intended as Win32, but the modifications for new get() and put()
routines may be independent of platform.

Thanks for your work supporting the forum and the library!

Regards,

Mark James
mark@james.net
Commit	Line	Data
	1	Frank,
	2
	3	I attached a file that uses RGBA interface (tif_getimage.c) to read a tiff
	4	file and convert to a DIB. It's advantage is that it is easy to read any
	5	tiff file suported by libtiff and easily convert it to a DIB. The disadvantage
	6	is that bilevel (B&W) bitmaps (and all other non-rgba images) are also
	7	converted to RGBA, thus taking up 32x as much memory as needed (4 bytes per
	8	pixel, rather than 1 bit). I read tiff files, but don't need to
	9	write them. And my files are typically small, so the overhead is mostly
	10	inconsequential. But for bilevel images, I overrode the get() and put()
	11	routines of the RGBA interface to just copy the data from the input raster
	12	to the output raster, rather than expanding out to full 32 bit format. It
	13	would be nice if there were a simple way to handle all palletized images,
	14	but that would take more custom routines, and it's not that important to me.
	15
	16	Usage:
	17
	18	m_pDIB = (PBITMAPINFOHEADER)::ReadTIFF(pathName);
	19	if (m_pDIB != 0) {
	20	m_format = IMAGETYPE_TIF;
	21	}
	22
	23	This is intended as Win32, but the modifications for new get() and put()
	24	routines may be independent of platform.
	25
	26	Thanks for your work supporting the forum and the library!
	27
	28	Regards,
	29
	30	Mark James
	31	mark@james.net