add find_trim

compiles, not yet working

ChangeLog

@@ -10,6 +10,7 @@
 - better prefix guessing on Windows, thanks tumagonx
 - savers support a "page_height" option for multipage save
 - rename 'disc' as 'memory' and default off
+- add vips_find_trim(), search for non-background areas 
 
 12/6/17 started 8.5.7
 - transform cmyk->rgb automatically on write if there's an embedded profile

libvips/arithmetic/Makefile.am

@@ -1,6 +1,7 @@
 noinst_LTLIBRARIES = libarithmetic.la
 
 libarithmetic_la_SOURCES = \
+	find_trim.c \
 	sum.c \
 	hough.c \
 	hough.h \

libvips/arithmetic/arithmetic.c

@@ -778,6 +778,7 @@ vips_arithmetic_operation_init( void )
 	extern GType vips_complex2_get_type( void ); 
 	extern GType vips_complexget_get_type( void ); 
 	extern GType vips_complexform_get_type( void ); 
+	extern GType vips_find_trim_get_type( void ); 
 
 	vips_add_get_type();
 	vips_sum_get_type();
@@ -816,4 +817,5 @@ vips_arithmetic_operation_init( void )
 	vips_complex2_get_type(); 
 	vips_complexget_get_type(); 
 	vips_complexform_get_type(); 
+	vips_find_trim_get_type(); 
 }

libvips/arithmetic/find_trim.c

@@ -0,0 +1,255 @@
+/* return the bounding box of the non-border part of the image
+ *
+ * 26/7/17
+ * 	- from a ruby example
+ */
+
+/*
+
+    This file is part of VIPS.
+    
+    VIPS is free software; you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+    02110-1301  USA
+
+ */
+
+/*
+
+    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
+
+ */
+
+/*
+#define VIPS_DEBUG
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif /*HAVE_CONFIG_H*/
+#include <vips/intl.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include <vips/vips.h>
+
+typedef struct _VipsFindTrim {
+	VipsOperation parent_instance;
+
+	VipsImage *in;
+	double threshold;
+
+	int left;
+	int top;
+	int width;
+	int height;
+
+	double *ones;
+	double *background;
+	int n;
+} VipsFindTrim;
+
+typedef VipsOperationClass VipsFindTrimClass;
+
+G_DEFINE_TYPE( VipsFindTrim, vips_find_trim, VIPS_TYPE_OPERATION );
+
+static void
+vips_find_trim_finalize( GObject *gobject )
+{
+	VipsFindTrim *find_trim = (VipsFindTrim *) gobject;
+
+#ifdef DEBUG
+	printf( "vips_find_trim_finalize: " );
+	vips_object_print_name( VIPS_OBJECT( gobject ) );
+	printf( "\n" );
+#endif /*DEBUG*/
+
+	VIPS_FREE( find_trim->background ); 
+	VIPS_FREE( find_trim->ones ); 
+
+	G_OBJECT_CLASS( vips_find_trim_parent_class )->finalize( gobject );
+}
+
+static int
+vips_find_trim_build( VipsObject *object )
+{
+	VipsFindTrim *find_trim = (VipsFindTrim *) object;
+	VipsImage **t = (VipsImage **) vips_object_local_array( object, 2 );
+
+	int i;
+	double *ones;
+	double d;
+
+	if( VIPS_OBJECT_CLASS( vips_find_trim_parent_class )->build( object ) )
+		return( -1 );
+
+	if( vips_image_decode( find_trim->in, &t[0] ) )
+		return( -1 ); 
+
+	/* Fetch pixel (0, 0) as the background value.
+	 */
+	if( vips_getpoint( t[0], 
+		&find_trim->background, &find_trim->n, 
+		0, 0, NULL ) )
+		return( -1 );
+
+	/* We want to subtract the bg.
+	 */
+	if( !(ones = VIPS_ARRAY( find_trim, find_trim->n, double )) )
+		return( -1 ); 
+	for( i = 0; i < find_trim->n; i++ ) {
+		ones[i] = 1.0;
+		find_trim->background[i] *= -1;
+	}
+
+	/* Smooth, find difference from bg, abs, threshold.
+	 */
+	if( vips_median( t[0], &t[1], 3, NULL ) ||
+		vips_linear( t[1], &t[2], 
+			ones, find_trim->background, find_trim->n, NULL ) ||
+		vips_abs( t[2], &t[3], NULL ) ||
+		vips_more_const1( t[3], &t[4], find_trim->threshold, NULL ) )
+		return( -1 ); 
+
+	/* t[5] == column sums, t[6] == row sums. 
+	 */
+	if( vips_project( t[4], &t[5], &t[6], NULL ) )
+		return( -1 );
+
+	/* t[8] == search column sums in from left.
+	 */
+	if( vips_profile( t[5], &t[7], &t[8], NULL ) ||
+		vips_avg( t[8], &d, NULL ) )
+		return( -1 );
+	find_trim->left = d;
+	if( vips_flip( t[5], &t[9], VIPS_DIRECTION_HORIZONTAL, NULL ) ||
+		vips_profile( t[9], &t[10], &t[11], NULL ) ||
+		vips_avg( t[11], &d, NULL ) )
+		return( -1 );
+	find_trim->width = (t[5]->Xsize - d) - find_trim->left;
+
+	/* t[8] == search column sums in from left.
+	 */
+	if( vips_profile( t[6], &t[12], &t[13], NULL ) ||
+		vips_avg( t[12], &d, NULL ) )
+		return( -1 );
+	find_trim->top = d;
+	if( vips_flip( t[6], &t[14], VIPS_DIRECTION_VERTICAL, NULL ) ||
+		vips_profile( t[14], &t[15], &t[16], NULL ) ||
+		vips_avg( t[15], &d, NULL ) )
+		return( -1 );
+	find_trim->height = (t[6]->Ysize - d) - find_trim->left;
+
+	return( 0 );
+}
+
+static void
+vips_find_trim_class_init( VipsFindTrimClass *class )
+{
+	GObjectClass *gobject_class = (GObjectClass *) class;
+	VipsObjectClass *object_class = (VipsObjectClass *) class;
+	VipsOperationClass *operation_class = VIPS_OPERATION_CLASS( class );
+
+	gobject_class->finalize = vips_find_trim_finalize;
+	gobject_class->set_property = vips_object_set_property;
+	gobject_class->get_property = vips_object_get_property;
+
+	object_class->nickname = "find_trim";
+	object_class->description = _( "search an image for non-edge areas" );
+	object_class->build = vips_find_trim_build;
+
+	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
+
+	VIPS_ARG_IMAGE( class, "in", 1,
+		_( "in" ), 
+		_( "Image to find_trim" ),
+		VIPS_ARGUMENT_REQUIRED_INPUT,
+		G_STRUCT_OFFSET( VipsFindTrim, in ) );
+
+	VIPS_ARG_DOUBLE( class, "threshold", 2, 
+		_( "Threshold" ), 
+		_( "Object threshold" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsFindTrim, threshold ),
+		0, INFINITY, 10.0 );
+
+	VIPS_ARG_INT( class, "left", 5, 
+		_( "Left" ), 
+		_( "Left edge of image" ),
+		VIPS_ARGUMENT_REQUIRED_OUTPUT,
+		G_STRUCT_OFFSET( VipsFindTrim, left ),
+		1, VIPS_MAX_COORD, 1 );
+
+	VIPS_ARG_INT( class, "top", 11, 
+		_( "Top" ), 
+		_( "Top edge of extract area" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsFindTrim, top ),
+		0, VIPS_MAX_COORD, 0 );
+
+	VIPS_ARG_INT( class, "width", 12, 
+		_( "Width" ), 
+		_( "Width of extract area" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsFindTrim, width ),
+		1, VIPS_MAX_COORD, 1 );
+
+	VIPS_ARG_INT( class, "height", 13, 
+		_( "Height" ), 
+		_( "Height of extract area" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsFindTrim, height ),
+		1, VIPS_MAX_COORD, 1 );
+
+}
+
+static void
+vips_find_trim_init( VipsFindTrim *find_trim )
+{
+	find_trim->threshold = 10;
+}
+
+/**
+ * vips_find_trim:
+ * @in: image to find_trim
+ * @left: output left edge
+ * @top: output top edge
+ * @width: output width
+ * @height: output height
+ * @...: %NULL-terminated list of optional named arguments
+ *
+ * Optional arguments:
+ *
+ * * @threshold: background / object threshold
+ *
+ * See also: vips_extract_area(), vips_smartcrop().
+ *
+ * Returns: 0 on success, -1 on error
+ */
+int
+vips_find_trim( VipsImage *in, 
+	int *left, int *top, int *width, int *height, ... )
+{
+	va_list ap;
+	int result;
+
+	va_start( ap, height );
+	result = vips_call_split( "find_trim", ap, in, 
+		left, top, width, height );
+	va_end( ap );
+
+	return( result );
+}

libvips/include/vips/arithmetic.h

@@ -384,6 +384,9 @@ int vips_stats( VipsImage *in, VipsImage **out, ... )
 	__attribute__((sentinel));
 int vips_measure( VipsImage *in, VipsImage **out, int h, int v, ... )
 	__attribute__((sentinel));
+int vips_find_trim( VipsImage *in, 
+	int *left, int *top, int *width, int *height, ... )
+	__attribute__((sentinel));
 int vips_getpoint( VipsImage *in, double **vector, int *n, int x, int y, ... )
 	__attribute__((sentinel));
 int vips_hist_find( VipsImage *in, VipsImage **out, ... )