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restore bandfmt after unpremultiply in thumbnail

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vips_unpremultiply() always outputs float. If you save the output of
vipsthumbnail to a format that supports float files, like tiff, it won't
ever get cast back to the source format.

Example:

	$ vipsheader Opera-icon-high-res.png
	Opera-icon-high-res.png: 3056x3325 uchar, 4 bands, srgb, pngload
	$ vipsthumbnail Opera-icon-high-res.png -o x.tif
	$ vipsheader x.tif
	x.tif: 117x128 float, 4 bands, scrgb, tiffload

This change makes it note and restore BandFmt aropund pre/unpremultiply.

See https://github.com/jcupitt/libvips/issues/447
This commit is contained in:
John Cupitt 2016-05-16 13:18:59 +01:00
parent db11d3b973
commit 54d8e4808f
2 changed files with 16 additions and 5 deletions
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1
ChangeLog
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@ -5,6 +5,7 @@
- dzsave won't write empty tiles in google mode, thanks bverem, perog,
felixbuenemann
- allow nested [] in CLI args
- restore BandFmt on unpremultiply in vipsthumbnail
15/4/16 started 8.3.1
- rename vips wrapper script, it was still vips-8.2, thanks Benjamin

20
tools/vipsthumbnail.c
View File

@ -77,6 +77,8 @@
* - add webp --shrink support
* 29/2/16
* - deprecate sharpen and interpolate
* 6/5/16
* - restore BandFmt after unpremultiply
*/
#ifdef HAVE_CONFIG_H
@ -363,6 +365,7 @@ thumbnail_shrink( VipsObject *process, VipsImage *in )
/* TRUE if we've premultiplied and need to unpremultiply.
*/
gboolean have_premultiplied;
VipsBandFormat unpremultiplied_format;
/* Sniff the incoming image and try to guess what the alpha max is.
*/
@ -444,8 +447,14 @@ thumbnail_shrink( VipsObject *process, VipsImage *in )
"max_alpha", max_alpha,
NULL ) )
return( NULL );
in = t[3];
have_premultiplied = TRUE;
/* vips_premultiply() makes a float image. When we
* vips_unpremultiply() below, we need to cast back to the
* pre-premultiply format.
*/
unpremultiplied_format = in->BandFmt;
in = t[3];
}
shrink = calculate_shrink( in );
@ -458,16 +467,17 @@ thumbnail_shrink( VipsObject *process, VipsImage *in )
vips_info( "vipsthumbnail", "unpremultiplying alpha" );
if( vips_unpremultiply( in, &t[5],
"max_alpha", max_alpha,
NULL ) )
NULL ) ||
vips_cast( t[5], &t[6], unpremultiplied_format, NULL ) )
return( NULL );
in = t[5];
in = t[6];
}
/* Colour management.
*
* If we've already imported, just export. Otherwise, we're in
* device space device and we need a combined
* import/export to transform to the target space.
* device space and we need a combined import/export to transform to
* the target space.
*/
if( have_imported ) {
if( export_profile ||