add @factor to bandunfold

TODO

@@ -1,4 +1,4 @@
-- bandunfold needs a @factor option too
+- tests for band fold/unfold with factor
 
 - how about something like vips_grid() which turns a tall thin one-band 
   image into a much smaller many-band image?

libvips/conversion/bandfold.c

@@ -74,7 +74,6 @@ vips_bandfold_gen( VipsRegion *or,
 {
 	VipsBandfold *bandfold = (VipsBandfold *) b;
 	VipsRegion *ir = (VipsRegion *) seq;
-	VipsImage *in = ir->im;
 	VipsImage *out = or->im;
 	VipsRect *r = &or->valid;
 	int psize = VIPS_IMAGE_SIZEOF_PEL( out );
@@ -82,16 +81,16 @@ vips_bandfold_gen( VipsRegion *or,
 	VipsRect need;
 	int y;
 
-	need.left = bandfold->factor * r->left;
+	need.left = r->left * bandfold->factor;
 	need.top = r->top;
-	need.width = bandfold->factor * r->width;
+	need.width = r->width * bandfold->factor;
 	need.height = r->height;
 	if( vips_region_prepare( ir, &need ) )
 		return( -1 );
 
 	for( y = 0; y < r->height; y++ ) {
 		VipsPel *p = VIPS_REGION_ADDR( ir, 
-			bandfold->factor * r->left, r->top + y );
+			r->left * bandfold->factor, r->top + y );
 		VipsPel *q = VIPS_REGION_ADDR( or, r->left, r->top + y );
 
 		/* We can't use vips_region_region() since we change pixel
@@ -190,7 +189,7 @@ vips_bandfold_init( VipsBandfold *bandfold )
  * @factor: fold by this factor
  *
  * Fold up an image horizontally: width is collapsed into bands. 
- * Set @factor to set how much to fold by: @factor 3, for example, will make
+ * Use @factor to set how much to fold by: @factor 3, for example, will make
  * the output image three times narrower than the input, and with three times
  * as many bands. By default the whole of the input width is folded up. 
  *

libvips/conversion/bandunfold.c

@@ -2,6 +2,8 @@
  *
  * 5/6/15
  * 	- from copy.c
+ * 10/6/15
+ * 	- add @factor option
  */
 
 /*
@@ -58,6 +60,8 @@ typedef struct _VipsBandunfold {
 	 */
 	VipsImage *in;
 
+	int factor;
+
 } VipsBandunfold;
 
 typedef VipsConversionClass VipsBandunfoldClass;
@@ -68,30 +72,34 @@ static int
 vips_bandunfold_gen( VipsRegion *or, 
 	void *seq, void *a, void *b, gboolean *stop )
 {
+	VipsBandunfold *bandunfold = (VipsBandunfold *) b;
 	VipsRegion *ir = (VipsRegion *) seq;
 	VipsImage *in = ir->im;
+	VipsImage *out = or->im;
 	VipsRect *r = &or->valid;
 	int esize = VIPS_IMAGE_SIZEOF_ELEMENT( in );
+	int psize = VIPS_IMAGE_SIZEOF_PEL( out );
 
 	VipsRect need;
 	int y;
 
-	need.left = 0;
+	need.left = r->left / bandunfold->factor;
 	need.top = r->top;
-	need.width = 1;
+	need.width = (1 + r->width) / bandunfold->factor;
 	need.height = r->height;
 	if( vips_region_prepare( ir, &need ) )
 		return( -1 );
 
 	for( y = 0; y < r->height; y++ ) {
-		VipsPel *p = VIPS_REGION_ADDR( ir, 0, r->top + y ) + 
-			r->left * esize;
+		VipsPel *p = VIPS_REGION_ADDR( ir, 
+			r->left / bandunfold->factor, r->top + y ) + 
+			(r->left % bandunfold->factor) * esize;
 		VipsPel *q = VIPS_REGION_ADDR( or, r->left, r->top + y );
 
 		/* We can't use vips_region_region() since we change pixel
 		 * coordinates.
 		 */
-		memcpy( q, p, r->width * esize );
+		memcpy( q, p, r->width * psize );
 	}
 
 	return( 0 );
@@ -100,6 +108,7 @@ vips_bandunfold_gen( VipsRegion *or,
 static int
 vips_bandunfold_build( VipsObject *object )
 {
+	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
 	VipsConversion *conversion = VIPS_CONVERSION( object );
 	VipsBandunfold *bandunfold = (VipsBandunfold *) object;
 
@@ -109,12 +118,20 @@ vips_bandunfold_build( VipsObject *object )
 	if( vips_image_pio_input( bandunfold->in ) )
 		return( -1 );
 
+	if( bandunfold->factor == 0 )
+		bandunfold->factor = bandunfold->in->Bands;
+	if( bandunfold->in->Bands % bandunfold->factor != 0 ) {
+		vips_error( class->nickname, 
+			"%s", _( "@factor must be a factor of image bands" ) );
+		return( -1 ); 
+	}
+
 	if( vips_image_pipelinev( conversion->out, 
 		VIPS_DEMAND_STYLE_THINSTRIP, bandunfold->in, NULL ) )
 		return( -1 );
 
-	conversion->out->Xsize *= bandunfold->in->Bands;
-	conversion->out->Bands = 1;
+	conversion->out->Xsize *= bandunfold->factor;
+	conversion->out->Bands /= bandunfold->factor;
 
 	if( vips_image_generate( conversion->out,
 		vips_start_one, vips_bandunfold_gen, vips_stop_one, 
@@ -148,11 +165,20 @@ vips_bandunfold_class_init( VipsBandunfoldClass *class )
 		VIPS_ARGUMENT_REQUIRED_INPUT,
 		G_STRUCT_OFFSET( VipsBandunfold, in ) );
 
+	VIPS_ARG_INT( class, "factor", 11, 
+		_( "Factor" ), 
+		_( "Unfold by this factor" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsBandunfold, factor ),
+		0, 10000000, 0 );
 }
 
 static void
 vips_bandunfold_init( VipsBandunfold *bandunfold )
 {
+	/* 0 means unfold by width, see above.
+	 */
+	bandunfold->factor = 0;
 }
 
 /**
@@ -161,8 +187,14 @@ vips_bandunfold_init( VipsBandunfold *bandunfold )
  * @out: output image
  * @...: %NULL-terminated list of optional named arguments
  *
- * Unfold image bands into x axis. @out has 1 band, and has width
- * equal to @in bands times @in width. 
+ * Optional arguments:
+ *
+ * @factor: unfold by this factor
+ *
+ * Unfold image bands into x axis. 
+ * Use @factor to set how much to unfold by: @factor 3, for example, will make
+ * the output image three times wider than the input, and with one third 
+ * as many bands. By default, all bands are unfolded.
  *
  * See also: vips_csvload(), vips_bandfold().
  *

libvips/foreign/csvload.c

@@ -189,7 +189,8 @@ vips_foreign_load_csv_init( VipsForeignLoadCsv *csv )
  * @separator: set of separator characters
  *
  * Load a CSV (comma-separated values) file. The output image is always 1 
- * band (monochrome), #VIPS_FORMAT_DOUBLE. 
+ * band (monochrome), #VIPS_FORMAT_DOUBLE. Use vips_bandfold() to turn
+ * RGBRGBRGB mono images into colour iamges. 
  *
  * Items in lines can be either floating point numbers in the C locale, or 
  * strings enclosed in double-quotes ("), or empty.
@@ -213,7 +214,7 @@ vips_foreign_load_csv_init( VipsForeignLoadCsv *csv )
  * @separator sets the characters that separate fields. 
  * Default ;,<emphasis>tab</emphasis>. Separators are never run together.
  *
- * See also: vips_image_new_from_file().
+ * See also: vips_image_new_from_file(), vips_bandfold().
  *
  * Returns: 0 on success, -1 on error.
  */