don't use Ping in magickload

it's too unreliable :-( we are forced to read every time

ChangeLog

@@ -22,7 +22,6 @@
 - add fontfile option to vips_text() [fangqiao]
 - add vips_transpose3d() -- swap major dimensions in a volumetric image
 - remove vips7 stuff from default API ... you must now #include it explicitly
-- acquire an image colormap if none set [jtorresfabra]
 - added vips_argument_get_id() to fix derived classes on win32 [angelmixu]
 
 12/3/18 started 8.6.4

configure.ac

@@ -704,17 +704,6 @@ if test x"$magick6" = x"yes"; then
   LIBS="$save_LIBS"
 fi
 
-if test x"$magick6" = x"yes"; then
-  # more recent magick6s have AcquireImageColormap rather than 
-  # AllocateImageColormap groan
-  save_LIBS="$LIBS"
-  LIBS="$LIBS $MAGICK_LIBS"
-  AC_CHECK_FUNCS(AcquireImageColormap,
-    AC_DEFINE(HAVE_ACQUIREIMAGECOLORMAP,1,
-	      [define if your magick has AcquireImageColormap.]))
-  LIBS="$save_LIBS"
-fi
-
 if test x"$magick6" = x"yes"; then
   # more recent magick6s have SetImageExtent 
   save_LIBS="$LIBS"

libvips/foreign/magick.c

@@ -52,12 +52,6 @@ magick_acquire_image( const ImageInfo *image_info, ExceptionInfo *exception )
 	return( AcquireImage( image_info, exception ) );
 }
 
-void
-magick_acquire_image_colormap( Image *image, int colors )
-{
-	AcquireImageColormap( image, colors )
-}
-
 void
 magick_acquire_next_image( const ImageInfo *image_info, Image *image,
 	ExceptionInfo *exception )
@@ -113,16 +107,6 @@ magick_acquire_image( const ImageInfo *image_info, ExceptionInfo *exception )
 #endif
 }
 
-void
-magick_acquire_image_colormap( Image *image, int colors )
-{
-#ifdef HAVE_ACQUIREIMAGECOLORMAP
-	AcquireImageColormap( image, colors ); 
-#else /*!HAVE_ACQUIREIMAGECOLORMAP*/
-	AllocateImageColormap( image, colors ); 
-#endif /*HAVE_ACQUIREIMAGECOLORMAP*/
-}
-
 void
 magick_acquire_next_image( const ImageInfo *image_info, Image *image,
 	ExceptionInfo *exception )

libvips/foreign/magick.h

@@ -44,7 +44,6 @@
 
 Image *magick_acquire_image( const ImageInfo *image_info, 
 	ExceptionInfo *exception );
-void magick_acquire_image_colormap( Image *image, int colors );
 void magick_acquire_next_image( const ImageInfo *image_info, 
 	Image *image, ExceptionInfo *exception );
 int magick_set_image_size( Image *image, 

libvips/foreign/magick2vips.c

@@ -58,7 +58,7 @@
  * 24/4/18
  * 	- add format hint
  * 25/5/18
- * 	- acquire an image colormap if none set
+ * 	- don't use Ping, it's too unreliable
  */
 
 /*
@@ -329,15 +329,6 @@ parse_header( Read *read )
 	if( (im->Bands = get_bands( image )) < 0 )
 		return( -1 );
 
-	/* Some ImageMagick loaders (eg. TGA) fail to set the ->colormap
-	 * field on Ping. GetImageChannelDepth() needs this and
-	 * will crash if it's not set.
-	 *
-	 * If there's no colormap, set an empty one.
-	 */
-	if( !image->colormap ) 
-		magick_acquire_image_colormap( image, image->colors );
-
 	/* Depth can be 'fractional'. 
 	 *
 	 * You'd think we should use
@@ -786,10 +777,6 @@ vips__magick_read( const char *filename,
 	return( 0 );
 }
 
-/* This has severe issues. See:
- *
- * http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=20017
- */
 int
 vips__magick_read_header( const char *filename, 
 	VipsImage *out, const char *format, const char *density, 
@@ -805,14 +792,18 @@ vips__magick_read_header( const char *filename,
 		return( -1 );
 
 #ifdef DEBUG
-	printf( "vips__magick_read_header: pinging image ...\n" );
+	printf( "vips__magick_read_header: reading image ...\n" );
 #endif /*DEBUG*/
 
-	read->image = PingImage( read->image_info, &read->exception );
+	/* It would be great if we could PingImage and just read the header,
+	 * but sadly many IM coders do not support ping. The critical one for
+	 * us is DICOM. TGA also has issues. 
+	 */
+	read->image = ReadImage( read->image_info, &read->exception );
 	if( !read->image ) {
 		magick_vips_error( "magick2vips", &read->exception );
 		vips_error( "magick2vips", 
-			_( "unable to ping file \"%s\"" ), filename ); 
+			_( "unable to read file \"%s\"" ), filename ); 
 		return( -1 );
 	}
 
@@ -885,7 +876,12 @@ vips__magick_read_buffer_header( const void *buf, const size_t len,
 	printf( "vips__magick_read_buffer_header: pinging blob ...\n" );
 #endif /*DEBUG*/
 
-	read->image = PingBlob( read->image_info, buf, len, &read->exception );
+	/* It would be great if we could PingBlob and just read the header,
+	 * but sadly many IM coders do not support ping well. The critical one 
+	 * for us is DICOM. TGA also has issues. 
+	 */
+	read->image = BlobToImage( read->image_info, 
+		buf, len, &read->exception );
 	if( !read->image ) {
 		magick_vips_error( "magick2vips", &read->exception );
 		vips_error( "magick2vips", "%s", _( "unable to ping blob" ) );