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make hist_equal output format match input format

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If the input image was ushort but had only uchar range, hist_equal would
output a uchar image, thanks to hist_norm's auto-clip feature. Make sure
this can't happen bu casting after the norm.

See https://github.com/jcupitt/libvips/issues/680

Thanks Simon Harris
This commit is contained in:
John Cupitt 2017-06-19 09:15:51 +01:00
parent dbf7729aee
commit 882c686553
1 changed files with 11 additions and 4 deletions
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15
libvips/histogram/hist_equal.c
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@ -15,6 +15,8 @@
* - gtkdoc
* 12/8/13
* - redone as a class
* 19/6/17
* - make output format always == input format, thanks Simon
*/
/*
@ -72,20 +74,24 @@ static int
vips_hist_equal_build( VipsObject *object )
{
VipsHistEqual *equal = (VipsHistEqual *) object;
VipsImage **t = (VipsImage **) vips_object_local_array( object, 4 );
VipsImage **t = (VipsImage **) vips_object_local_array( object, 5 );
g_object_set( equal, "out", vips_image_new(), NULL );
if( VIPS_OBJECT_CLASS( vips_hist_equal_parent_class )->build( object ) )
return( -1 );
/* norm can return a uchar output for a ushort input if the range is
* small, so make sure we cast back to the input type again.
*/
if( vips_hist_find( equal->in, &t[0],
"band", equal->which,
NULL ) ||
vips_hist_cum( t[0], &t[1], NULL ) ||
vips_hist_norm( t[1], &t[2], NULL ) ||
vips_maplut( equal->in, &t[3], t[2], NULL ) ||
vips_image_write( t[3], equal->out ) )
vips_cast( t[2], &t[3], equal->in->BandFmt, NULL ) ||
vips_maplut( equal->in, &t[4], t[3], NULL ) ||
vips_image_write( t[4], equal->out ) )
return( -1 );
return( 0 );
@ -141,7 +147,8 @@ vips_hist_equal_init( VipsHistEqual *equal )
* * @band: band to equalise
*
* Histogram-equalise @in. Equalise using band @bandno, or if @bandno is -1,
* equalise bands independently.
* equalise bands independently. The output format is always the same as the
* input format.
*
* See also:
*