add password fielf to pdfiumload

and docs

libvips/foreign/foreign.c

@@ -2583,6 +2583,7 @@ vips_jxlsave_target( VipsImage *in, VipsTarget *target, ... )
  * * @dpi: %gdouble, render at this DPI
  * * @scale: %gdouble, scale render by this factor
  * * @background: #VipsArrayDouble background colour
+ * * @password: %gchararray background colour
  *
  * Render a PDF file into a VIPS image. 
  *
@@ -2603,6 +2604,8 @@ vips_jxlsave_target( VipsImage *in, VipsTarget *target, ... )
  * Use @background to set the background RGBA colour. The default is 255 
  * (solid white), use eg. 0 for a transparent background.
  *
+ * Use @password to supply a decryption password.
+ *
  * The operation fills a number of header fields with metadata, for example
  * "pdf-author". They may be useful. 
  *

libvips/foreign/pdfiumload.c

@@ -12,6 +12,8 @@
  * 	- have a lock just for pdfium [DarthSim]
  * 	- update for current pdfium
  * 	- add _source input
+ * 28/1/22
+ * 	- add password
  */
 
 /*
@@ -130,6 +132,10 @@ typedef struct _VipsForeignLoadPdf {
 	 */
 	VipsArrayDouble *background;
 
+	/* Decrypt with this.
+	 */
+	const char *password;
+
 	FPDF_FILEACCESS file_access;
 	FPDF_DOCUMENT doc;
 	FPDF_PAGE page;
@@ -281,7 +287,7 @@ vips_foreign_load_pdf_build( VipsObject *object )
 		g_mutex_lock( vips_pdfium_mutex );
 
 		if( !(pdf->doc = FPDF_LoadCustomDocument( &pdf->file_access, 
-			NULL )) ) {
+			pdf->password )) ) {
 			g_mutex_unlock( vips_pdfium_mutex );
 			vips_pdfium_error();
 			vips_error( "pdfload", 
@@ -693,6 +699,13 @@ vips_foreign_load_pdf_class_init( VipsForeignLoadPdfClass *class )
 		G_STRUCT_OFFSET( VipsForeignLoadPdf, background ),
 		VIPS_TYPE_ARRAY_DOUBLE );
 
+	VIPS_ARG_STRING( class, "password", 25, 
+		_( "Password" ), 
+		_( "Decrypt with this password" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsForeignLoadPdf, password ),
+		NULL );
+
 }
 
 static void

libvips/foreign/popplerload.c

@@ -20,6 +20,8 @@
  * 	- allow dpi and scale to both be set [le0daniel]
  * 21/4/21 kleisauke
  * 	- include GObject part from pdfload.c
+ * 28/1/22
+ * 	- add password
  */
 
 /*