add page-height to pdfload

TODO

@@ -1,6 +1,42 @@
 - all toilet roll loaders need to set "page-height"
 
-  magick, pdf and tiff need to use the same page/n interface
+  magick, pdf, gif and tiff need to use the same page/n interface
+
+  magick: has page and all_frames
+
+  	deprecate all_frames, add @n, make all_frames set n == -1 
+
+	do we allow page + all_frames?
+
+	need to check magick2vips.c and magick7load.c 
+
+	add page-height
+
+  magick6
+
+	john@kiwi:~/pics$ vips magickload nipguide.pdf x.v --all-frames
+	john@kiwi:~/pics$ vipsheader x.v
+	x.v: 595x842 ushort, 2 bands, grey16, magickload
+
+  	argh
+
+  magick7
+
+	$ vips magickload nipguide.pdf x.v --all-frames
+	$ vipsheader x.v
+	x.v: 595x48836 ushort, 4 bands, rgb16, magickload
+
+	phew
+
+  gifload has page, but no n
+
+  	add an n param
+
+	add page-height
+
+  pdfload has page, n, allows n == -1, sets page-height
+
+
 
 
 

libvips/foreign/magickload.c

@@ -308,6 +308,7 @@ vips_foreign_load_magick_buffer_init( VipsForeignLoadMagickBuffer *buffer )
  * Optional arguments:
  *
  * * @all_frames: %gboolean, load all frames in sequence
+ * * @page: %gint, load from this page
  * * @density: string, canvas resolution for rendering vector formats like SVG
  *
  * Read in an image using libMagick, the ImageMagick library. This library can
@@ -355,6 +356,7 @@ vips_magickload( const char *filename, VipsImage **out, ... )
  * Optional arguments:
  *
  * * @all_frames: %gboolean, load all frames in sequence
+ * * @page: %gint, load from this page
  * * @density: string, canvas resolution for rendering vector formats like SVG
  *
  * Read an image memory block using libMagick into a VIPS image. Exactly as

libvips/foreign/pdfload.c

@@ -4,6 +4,8 @@
  * 	- from openslideload.c
  * 12/5/16
  * 	- add @n ... number of pages to load
+ * 23/11/16
+ * 	- set page-height, if we can
  */
 
 /*
@@ -309,6 +311,17 @@ vips_foreign_load_pdf_header( VipsForeignLoad *load )
 		top += pdf->pages[i].height;
 	}
 
+	/* If all pages are the same size, we can tag this as a toilet roll
+	 * image and tiffsave will be able to save it as a multipage tiff.
+	 */
+	for( i = 1; i < pdf->n; i++ ) 
+		if( pdf->pages[i].width != pdf->pages[0].width ||
+			pdf->pages[i].height != pdf->pages[0].height )
+			break;
+	if( i == pdf->n ) 
+		vips_image_set_int( load->out, 
+			VIPS_META_PAGE_HEIGHT, pdf->pages[0].height );
+
 	vips_foreign_load_pdf_set_image( pdf, load->out ); 
 
 	return( 0 );