add n-pages metadata item

tiff, magick and pdf load now attach an n-pages metadata item recording
the number of pages in the orginal file

see https://github.com/jcupitt/libvips/issues/953

ChangeLog

@@ -18,6 +18,7 @@
 - add @format option to magickload
 - jpegload adds a jpeg-chroma-subsample field with eg. 4:4:4 for no
   chrominance subsampling. 
+- tiffload, pdfload, magickload set VIPS_META_N_PAGES "n-pages" metadata item
 
 12/3/18 started 8.6.4
 - better fitting of fonts with overhanging edges [Adrià]

libvips/foreign/magick2vips.c

@@ -134,7 +134,14 @@ typedef struct _Read {
 	ImageInfo *image_info;
 	ExceptionInfo exception;
 
+	/* Number of pages in image.
+	 */
+	int n_pages;
+
+	/* Number of pages we will read.
+	 */
 	int n_frames;
+
 	Image **frames;
 	int frame_height;
 
@@ -203,6 +210,7 @@ read_new( const char *filename, VipsImage *im,
 	read->image = NULL;
 	read->image_info = CloneImageInfo( NULL );
 	GetExceptionInfo( &read->exception );
+	read->n_pages = 0;
 	read->n_frames = 0;
 	read->frames = NULL;
 	read->frame_height = 0;
@@ -488,6 +496,7 @@ parse_header( Read *read )
 		which says this is a volumetric image
 
 	 */
+	read->n_pages = GetImageListLength( image );
 	read->n_frames = 0;
 	for( p = image; p; (p = GetNextImageInList( p )) ) {
 		if( p->columns != (unsigned int) im->Xsize ||
@@ -512,7 +521,7 @@ parse_header( Read *read )
 		read->n_frames = 1;
 
 #ifdef DEBUG
-	printf( "image has %d frames\n", read->n_frames );
+	printf( "will read %d frames\n", read->n_frames );
 #endif /*DEBUG*/
 
 	if( read->n != -1 )
@@ -533,6 +542,8 @@ parse_header( Read *read )
 		im->Ysize *= read->n_frames;
 	}
 
+	vips_image_set_int( im, VIPS_META_N_PAGES, read->n_pages );
+
 	return( 0 );
 }
 

libvips/foreign/magick7load.c

@@ -76,7 +76,11 @@ typedef struct _VipsForeignLoadMagick7 {
 	ImageInfo *image_info;
 	ExceptionInfo *exception;
 
-	int n_frames;			/* Number of frames in file */
+	/* Number of pages in image.
+	 */
+	int n_pages;
+
+	int n_frames;			/* Number of frames we will read */
 	Image **frames;			/* An Image* for each frame */
 	CacheView **cache_view; 	/* A CacheView for each frame */
 	int frame_height;	
@@ -283,26 +287,6 @@ vips_foreign_load_magick7_dispose( GObject *gobject )
 		dispose( gobject );
 }
 
-static void *
-vips_foreign_load_magick7_genesis_cb( void *client )
-{
-#ifdef DEBUG
-	printf( "vips_foreign_load_magick7_genesis:\n" ); 
-#endif /*DEBUG*/
-
-	MagickCoreGenesis( vips_get_argv0(), MagickFalse );
-
-	return( NULL );
-}
-
-static void
-vips_foreign_load_magick7_genesis( void )
-{
-	static GOnce once = G_ONCE_INIT;
-
-	VIPS_ONCE( &once, vips_foreign_load_magick7_genesis_cb, NULL );
-}
-
 static int
 vips_foreign_load_magick7_build( VipsObject *object )
 {
@@ -578,14 +562,15 @@ vips_foreign_load_magick7_parse( VipsForeignLoadMagick7 *magick7,
 		which says this is a volumetric image
 
 	 */
-	magick7->n_frames = GetImageListLength( GetFirstImageInList( image ) );
+	magick7->n_pages = GetImageListLength( GetFirstImageInList( image ) );
 
 #ifdef DEBUG
-	printf( "image has %d frames\n", magick7->n_frames );
+	printf( "image has %d pages\n", magick7->n_pages );
 #endif /*DEBUG*/
 
-	if( magick7->n != -1 )
-		magick7->n_frames = VIPS_MIN( magick7->n_frames, magick7->n );
+	magick7->n_frames = magick7->n != -1 ?
+		VIPS_MIN( magick7->n_frames, magick7->n ) :
+		magick7->n_pages;
 
 	/* So we can finally set the height.
 	 */
@@ -594,11 +579,13 @@ vips_foreign_load_magick7_parse( VipsForeignLoadMagick7 *magick7,
 		out->Ysize *= magick7->n_frames;
 	}
 
+	vips_image_set_int( out, VIPS_META_N_PAGES, magick7->n_pages );
+
 	return( 0 );
 }
 
 /* We don't bother with GetPixelReadMask(), assume it's everywhere. Don't
- * bother with traits, assume taht's always update.
+ * bother with traits, assume that's always updated.
  *
  * We do skip index channels. Palette images add extra index channels
  * containing the index value from the file before colourmap lookup.
@@ -753,7 +740,7 @@ ismagick7( const char *filename )
 	ExceptionInfo *exception;
 	int result;
 
-	vips_foreign_load_magick7_genesis();
+	magick_genesis();
 
 	/* Horribly slow :-(
 	 */
@@ -853,7 +840,7 @@ vips_foreign_load_magick7_buffer_is_a_buffer( const void *buf, size_t len )
 	ExceptionInfo *exception;
 	int result;
 
-	vips_foreign_load_magick7_genesis();
+	magick_genesis();
 
 	/* Horribly slow :-(
 	 */

libvips/foreign/pdfload.c

@@ -204,9 +204,10 @@ vips_foreign_load_pdf_set_image( VipsForeignLoadPdf *pdf, VipsImage *out )
 	 */
         vips_image_pipelinev( out, VIPS_DEMAND_STYLE_FATSTRIP, NULL );
 
-	/* Extract and attach metadata.
+	/* Extract and attach metadata. Set the old name too for compat.
 	 */
 	vips_image_set_int( out, "pdf-n_pages", pdf->n_pages ); 
+	vips_image_set_int( out, VIPS_META_N_PAGES, pdf->n_pages );
 
 	for( i = 0; i < n_metadata; i++ ) {
 		VipsForeignLoadPdfMetadata *metadata = 

libvips/foreign/pdfload_pdfium.c

@@ -241,9 +241,10 @@ vips_foreign_load_pdf_set_image( VipsForeignLoadPdf *pdf, VipsImage *out )
 	 */
         vips_image_pipelinev( out, VIPS_DEMAND_STYLE_FATSTRIP, NULL );
 
-	/* Extract and attach metadata.
+	/* Extract and attach metadata. Set the old name too for compat.
 	 */
 	vips_image_set_int( out, "pdf-n_pages", pdf->n_pages ); 
+	vips_image_set_int( out, VIPS_META_N_PAGES, pdf->n_pages ); 
 
 	for( i = 0; i < n_metadata; i++ ) {
 		VipsForeignLoadPdfMetadata *metadata = 

libvips/foreign/tiff2vips.c

@@ -177,6 +177,8 @@
  * 	- remove missing res warning
  * 19/5/17
  * 	- page > 0 could break edge tiles or strips
+ * 26/4/18
+ * 	- add n-pages metadata item
  */
 
 /*
@@ -283,6 +285,10 @@ typedef struct _Rtiff {
 	 */
 	TIFF *tiff;
 
+	/* Number of pages (directories) in image.
+	 */
+	int n_pages;
+
 	/* The current page we have set.
 	 */
 	int current_page;
@@ -1230,6 +1236,8 @@ rtiff_set_header( Rtiff *rtiff, VipsImage *out )
 		vips_image_set_int( out, 
 			VIPS_META_PAGE_HEIGHT, rtiff->header.height );
 
+	vips_image_set_int( out, VIPS_META_N_PAGES, rtiff->n_pages );
+
 	/* Even though we could end up serving tiled data, always hint
 	 * THINSTRIP, since we're quite happy doing that too, and it could need
 	 * a lot less memory.
@@ -1984,6 +1992,7 @@ rtiff_new( VipsImage *out, int page, int n, gboolean autorotate )
 	rtiff->n = n;
 	rtiff->autorotate = autorotate;
 	rtiff->tiff = NULL;
+	rtiff->n_pages = 0;
 	rtiff->current_page = -1;
 	rtiff->sfn = NULL;
 	rtiff->client = NULL;
@@ -2167,8 +2176,9 @@ rtiff_header_read_all( Rtiff *rtiff )
 
 	/* -1 means "to the end".
 	 */
+	rtiff->n_pages = rtiff_n_pages( rtiff );
 	if( rtiff->n == -1 )
-		rtiff->n = rtiff_n_pages( rtiff ) - rtiff->page;
+		rtiff->n = rtiff->n_pages - rtiff->page;
 
 	/* If we're to read many pages, verify that they are all identical. 
 	 */

libvips/include/vips/header.h

@@ -143,6 +143,13 @@ extern "C" {
  */
 #define VIPS_META_PAGE_HEIGHT "page-height"
 
+/**
+ * VIPS_META_N_PAGES:
+ *
+ * If set, the number of pages in the original file. 
+ */
+#define VIPS_META_N_PAGES "n-pages"
+
 guint64 vips_format_sizeof( VipsBandFormat format );
 guint64 vips_format_sizeof_unsafe( VipsBandFormat format );